/*
** 2004 April 6
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This file implements an external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"
/*
** The header string that appears at the beginning of every
** SQLite database.
*/
static const char zMagicHeader[] = SQLITE_FILE_HEADER;
/*
** Set this global variable to 1 to enable tracing using the TRACE
** macro.
*/
#if 0
int sqlite3BtreeTrace=1; /* True to enable tracing */
# define TRACE(X) if(sqlite3BtreeTrace){printf X;fflush(stdout);}
#else
# define TRACE(X)
#endif
/*
** Extract a 2-byte big-endian integer from an array of unsigned bytes.
** But if the value is zero, make it 65536.
**
** This routine is used to extract the "offset to cell content area" value
** from the header of a btree page. If the page size is 65536 and the page
** is empty, the offset should be 65536, but the 2-byte value stores zero.
** This routine makes the necessary adjustment to 65536.
*/
#define get2byteNotZero(X) (((((int)get2byte(X))-1)&0xffff)+1)
/*
** Values passed as the 5th argument to allocateBtreePage()
*/
#define BTALLOC_ANY 0 /* Allocate any page */
#define BTALLOC_EXACT 1 /* Allocate exact page if possible */
#define BTALLOC_LE 2 /* Allocate any page <= the parameter */
/*
** Macro IfNotOmitAV(x) returns (x) if SQLITE_OMIT_AUTOVACUUM is not
** defined, or 0 if it is. For example:
**
** bIncrVacuum = IfNotOmitAV(pBtShared->incrVacuum);
*/
#ifndef SQLITE_OMIT_AUTOVACUUM
#define IfNotOmitAV(expr) (expr)
#else
#define IfNotOmitAV(expr) 0
#endif
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** A list of BtShared objects that are eligible for participation
** in shared cache. This variable has file scope during normal builds,
** but the test harness needs to access it so we make it global for
** test builds.
**
** Access to this variable is protected by SQLITE_MUTEX_STATIC_MASTER.
*/
#ifdef SQLITE_TEST
BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
#else
static BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
#endif
#endif /* SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Enable or disable the shared pager and schema features.
**
** This routine has no effect on existing database connections.
** The shared cache setting effects only future calls to
** sqlite3_open(), sqlite3_open16(), or sqlite3_open_v2().
*/
int sqlite3_enable_shared_cache(int enable){
sqlite3GlobalConfig.sharedCacheEnabled = enable;
return SQLITE_OK;
}
#endif
#ifdef SQLITE_OMIT_SHARED_CACHE
/*
** The functions querySharedCacheTableLock(), setSharedCacheTableLock(),
** and clearAllSharedCacheTableLocks()
** manipulate entries in the BtShared.pLock linked list used to store
** shared-cache table level locks. If the library is compiled with the
** shared-cache feature disabled, then there is only ever one user
** of each BtShared structure and so this locking is not necessary.
** So define the lock related functions as no-ops.
*/
#define querySharedCacheTableLock(a,b,c) SQLITE_OK
#define setSharedCacheTableLock(a,b,c) SQLITE_OK
#define clearAllSharedCacheTableLocks(a)
#define downgradeAllSharedCacheTableLocks(a)
#define hasSharedCacheTableLock(a,b,c,d) 1
#define hasReadConflicts(a, b) 0
#endif
#ifndef SQLITE_OMIT_SHARED_CACHE
#ifdef SQLITE_DEBUG
/*
**** This function is only used as part of an assert() statement. ***
**
** Check to see if pBtree holds the required locks to read or write to the
** table with root page iRoot. Return 1 if it does and 0 if not.
**
** For example, when writing to a table with root-page iRoot via
** Btree connection pBtree:
**
** assert( hasSharedCacheTableLock(pBtree, iRoot, 0, WRITE_LOCK) );
**
** When writing to an index that resides in a sharable database, the
** caller should have first obtained a lock specifying the root page of
** the corresponding table. This makes things a bit more complicated,
** as this module treats each table as a separate structure. To determine
** the table corresponding to the index being written, this
** function has to search through the database schema.
**
** Instead of a lock on the table/index rooted at page iRoot, the caller may
** hold a write-lock on the schema table (root page 1). This is also
** acceptable.
*/
static int hasSharedCacheTableLock(
Btree *pBtree, /* Handle that must hold lock */
Pgno iRoot, /* Root page of b-tree */
int isIndex, /* True if iRoot is the root of an index b-tree */
int eLockType /* Required lock type (READ_LOCK or WRITE_LOCK) */
){
Schema *pSchema = (Schema *)pBtree->pBt->pSchema;
Pgno iTab = 0;
BtLock *pLock;
/* If this database is not shareable, or if the client is reading
** and has the read-uncommitted flag set, then no lock is required.
** Return true immediately.
*/
if( (pBtree->sharable==0)
|| (eLockType==READ_LOCK && (pBtree->db->flags & SQLITE_ReadUncommitted))
){
return 1;
}
/* If the client is reading or writing an index and the schema is
** not loaded, then it is too difficult to actually check to see if
** the correct locks are held. So do not bother - just return true.
** This case does not come up very often anyhow.
*/
if( isIndex && (!pSchema || (pSchema->schemaFlags&DB_SchemaLoaded)==0) ){
return 1;
}
/* Figure out the root-page that the lock should be held on. For table
** b-trees, this is just the root page of the b-tree being read or
** written. For index b-trees, it is the root page of the associated
** table. */
if( isIndex ){
HashElem *p;
for(p=sqliteHashFirst(&pSchema->idxHash); p; p=sqliteHashNext(p)){
Index *pIdx = (Index *)sqliteHashData(p);
if( pIdx->tnum==(int)iRoot ){
if( iTab ){
/* Two or more indexes share the same root page. There must
** be imposter tables. So just return true. The assert is not
** useful in that case. */
return 1;
}
iTab = pIdx->pTable->tnum;
}
}
}else{
iTab = iRoot;
}
/* Search for the required lock. Either a write-lock on root-page iTab, a
** write-lock on the schema table, or (if the client is reading) a
** read-lock on iTab will suffice. Return 1 if any of these are found. */
for(pLock=pBtree->pBt->pLock; pLock; pLock=pLock->pNext){
if( pLock->pBtree==pBtree
&& (pLock->iTable==iTab || (pLock->eLock==WRITE_LOCK && pLock->iTable==1))
&& pLock->eLock>=eLockType
){
return 1;
}
}
/* Failed to find the required lock. */
return 0;
}
#endif /* SQLITE_DEBUG */
#ifdef SQLITE_DEBUG
/*
**** This function may be used as part of assert() statements only. ****
**
** Return true if it would be illegal for pBtree to write into the
** table or index rooted at iRoot because other shared connections are
** simultaneously reading that same table or index.
**
** It is illegal for pBtree to write if some other Btree object that
** shares the same BtShared object is currently reading or writing
** the iRoot table. Except, if the other Btree object has the
** read-uncommitted flag set, then it is OK for the other object to
** have a read cursor.
**
** For example, before writing to any part of the table or index
** rooted at page iRoot, one should call:
**
** assert( !hasReadConflicts(pBtree, iRoot) );
*/
static int hasReadConflicts(Btree *pBtree, Pgno iRoot){
BtCursor *p;
for(p=pBtree->pBt->pCursor; p; p=p->pNext){
if( p->pgnoRoot==iRoot
&& p->pBtree!=pBtree
&& 0==(p->pBtree->db->flags & SQLITE_ReadUncommitted)
){
return 1;
}
}
return 0;
}
#endif /* #ifdef SQLITE_DEBUG */
/*
** Query to see if Btree handle p may obtain a lock of type eLock
** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return
** SQLITE_OK if the lock may be obtained (by calling
** setSharedCacheTableLock()), or SQLITE_LOCKED if not.
*/
static int querySharedCacheTableLock(Btree *p, Pgno iTab, u8 eLock){
BtShared *pBt = p->pBt;
BtLock *pIter;
assert( sqlite3BtreeHoldsMutex(p) );
assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
assert( p->db!=0 );
assert( !(p->db->flags&SQLITE_ReadUncommitted)||eLock==WRITE_LOCK||iTab==1 );
/* If requesting a write-lock, then the Btree must have an open write
** transaction on this file. And, obviously, for this to be so there
** must be an open write transaction on the file itself.
*/
assert( eLock==READ_LOCK || (p==pBt->pWriter && p->inTrans==TRANS_WRITE) );
assert( eLock==READ_LOCK || pBt->inTransaction==TRANS_WRITE );
/* This routine is a no-op if the shared-cache is not enabled */
if( !p->sharable ){
return SQLITE_OK;
}
/* If some other connection is holding an exclusive lock, the
** requested lock may not be obtained.
*/
if( pBt->pWriter!=p && (pBt->btsFlags & BTS_EXCLUSIVE)!=0 ){
sqlite3ConnectionBlocked(p->db, pBt->pWriter->db);
return SQLITE_LOCKED_SHAREDCACHE;
}
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
/* The condition (pIter->eLock!=eLock) in the following if(...)
** statement is a simplification of:
**
** (eLock==WRITE_LOCK || pIter->eLock==WRITE_LOCK)
**
** since we know that if eLock==WRITE_LOCK, then no other connection
** may hold a WRITE_LOCK on any table in this file (since there can
** only be a single writer).
*/
assert( pIter->eLock==READ_LOCK || pIter->eLock==WRITE_LOCK );
assert( eLock==READ_LOCK || pIter->pBtree==p || pIter->eLock==READ_LOCK);
if( pIter->pBtree!=p && pIter->iTable==iTab && pIter->eLock!=eLock ){
sqlite3ConnectionBlocked(p->db, pIter->pBtree->db);
if( eLock==WRITE_LOCK ){
assert( p==pBt->pWriter );
pBt->btsFlags |= BTS_PENDING;
}
return SQLITE_LOCKED_SHAREDCACHE;
}
}
return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Add a lock on the table with root-page iTable to the shared-btree used
** by Btree handle p. Parameter eLock must be either READ_LOCK or
** WRITE_LOCK.
**
** This function assumes the following:
**
** (a) The specified Btree object p is connected to a sharable
** database (one with the BtShared.sharable flag set), and
**
** (b) No other Btree objects hold a lock that conflicts
** with the requested lock (i.e. querySharedCacheTableLock() has
** already been called and returned SQLITE_OK).
**
** SQLITE_OK is returned if the lock is added successfully. SQLITE_NOMEM
** is returned if a malloc attempt fails.
*/
static int setSharedCacheTableLock(Btree *p, Pgno iTable, u8 eLock){
BtShared *pBt = p->pBt;
BtLock *pLock = 0;
BtLock *pIter;
assert( sqlite3BtreeHoldsMutex(p) );
assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
assert( p->db!=0 );
/* A connection with the read-uncommitted flag set will never try to
** obtain a read-lock using this function. The only read-lock obtained
** by a connection in read-uncommitted mode is on the sqlite_master
** table, and that lock is obtained in BtreeBeginTrans(). */
assert( 0==(p->db->flags&SQLITE_ReadUncommitted) || eLock==WRITE_LOCK );
/* This function should only be called on a sharable b-tree after it
** has been determined that no other b-tree holds a conflicting lock. */
assert( p->sharable );
assert( SQLITE_OK==querySharedCacheTableLock(p, iTable, eLock) );
/* First search the list for an existing lock on this table. */
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->iTable==iTable && pIter->pBtree==p ){
pLock = pIter;
break;
}
}
/* If the above search did not find a BtLock struct associating Btree p
** with table iTable, allocate one and link it into the list.
*/
if( !pLock ){
pLock = (BtLock *)sqlite3MallocZero(sizeof(BtLock));
if( !pLock ){
return SQLITE_NOMEM_BKPT;
}
pLock->iTable = iTable;
pLock->pBtree = p;
pLock->pNext = pBt->pLock;
pBt->pLock = pLock;
}
/* Set the BtLock.eLock variable to the maximum of the current lock
** and the requested lock. This means if a write-lock was already held
** and a read-lock requested, we don't incorrectly downgrade the lock.
*/
assert( WRITE_LOCK>READ_LOCK );
if( eLock>pLock->eLock ){
pLock->eLock = eLock;
}
return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Release all the table locks (locks obtained via calls to
** the setSharedCacheTableLock() procedure) held by Btree object p.
**
** This function assumes that Btree p has an open read or write
** transaction. If it does not, then the BTS_PENDING flag
** may be incorrectly cleared.
*/
static void clearAllSharedCacheTableLocks(Btree *p){
BtShared *pBt = p->pBt;
BtLock **ppIter = &pBt->pLock;
assert( sqlite3BtreeHoldsMutex(p) );
assert( p->sharable || 0==*ppIter );
assert( p->inTrans>0 );
while( *ppIter ){
BtLock *pLock = *ppIter;
assert( (pBt->btsFlags & BTS_EXCLUSIVE)==0 || pBt->pWriter==pLock->pBtree );
assert( pLock->pBtree->inTrans>=pLock->eLock );
if( pLock->pBtree==p ){
*ppIter = pLock->pNext;
assert( pLock->iTable!=1 || pLock==&p->lock );
if( pLock->iTable!=1 ){
sqlite3_free(pLock);
}
}else{
ppIter = &pLock->pNext;
}
}
assert( (pBt->btsFlags & BTS_PENDING)==0 || pBt->pWriter );
if( pBt->pWriter==p ){
pBt->pWriter = 0;
pBt->btsFlags &= ~(BTS_EXCLUSIVE|BTS_PENDING);
}else if( pBt->nTransaction==2 ){
/* This function is called when Btree p is concluding its
** transaction. If there currently exists a writer, and p is not
** that writer, then the number of locks held by connections other
** than the writer must be about to drop to zero. In this case
** set the BTS_PENDING flag to 0.
**
** If there is not currently a writer, then BTS_PENDING must
** be zero already. So this next line is harmless in that case.
*/
pBt->btsFlags &= ~BTS_PENDING;
}
}
/*
** This function changes all write-locks held by Btree p into read-locks.
*/
static void downgradeAllSharedCacheTableLocks(Btree *p){
BtShared *pBt = p->pBt;
if( pBt->pWriter==p ){
BtLock *pLock;
pBt->pWriter = 0;
pBt->btsFlags &= ~(BTS_EXCLUSIVE|BTS_PENDING);
for(pLock=pBt->pLock; pLock; pLock=pLock->pNext){
assert( pLock->eLock==READ_LOCK || pLock->pBtree==p );
pLock->eLock = READ_LOCK;
}
}
}
#endif /* SQLITE_OMIT_SHARED_CACHE */
static void releasePage(MemPage *pPage); /* Forward reference */
/*
***** This routine is used inside of assert() only ****
**
** Verify that the cursor holds the mutex on its BtShared
*/
#ifdef SQLITE_DEBUG
static int cursorHoldsMutex(BtCursor *p){
return sqlite3_mutex_held(p->pBt->mutex);
}
/* Verify that the cursor and the BtShared agree about what is the current
** database connetion. This is important in shared-cache mode. If the database
** connection pointers get out-of-sync, it is possible for routines like
** btreeInitPage() to reference an stale connection pointer that references a
** a connection that has already closed. This routine is used inside assert()
** statements only and for the purpose of double-checking that the btree code
** does keep the database connection pointers up-to-date.
*/
static int cursorOwnsBtShared(BtCursor *p){
assert( cursorHoldsMutex(p) );
return (p->pBtree->db==p->pBt->db);
}
#endif
/*
** Invalidate the overflow cache of the cursor passed as the first argument.
** on the shared btree structure pBt.
*/
#define invalidateOverflowCache(pCur) (pCur->curFlags &= ~BTCF_ValidOvfl)
/*
** Invalidate the overflow page-list cache for all cursors opened
** on the shared btree structure pBt.
*/
static void invalidateAllOverflowCache(BtShared *pBt){
BtCursor *p;
assert( sqlite3_mutex_held(pBt->mutex) );
for(p=pBt->pCursor; p; p=p->pNext){
invalidateOverflowCache(p);
}
}
#ifndef SQLITE_OMIT_INCRBLOB
/*
** This function is called before modifying the contents of a table
** to invalidate any incrblob cursors that are open on the
** row or one of the rows being modified.
**
** If argument isClearTable is true, then the entire contents of the
** table is about to be deleted. In this case invalidate all incrblob
** cursors open on any row within the table with root-page pgnoRoot.
**
** Otherwise, if argument isClearTable is false, then the row with
** rowid iRow is being replaced or deleted. In this case invalidate
** only those incrblob cursors open on that specific row.
*/
static void invalidateIncrblobCursors(
Btree *pBtree, /* The database file to check */
i64 iRow, /* The rowid that might be changing */
int isClearTable /* True if all rows are being deleted */
){
BtCursor *p;
if( pBtree->hasIncrblobCur==0 ) return;
assert( sqlite3BtreeHoldsMutex(pBtree) );
pBtree->hasIncrblobCur = 0;
for(p=pBtree->pBt->pCursor; p; p=p->pNext){
if( (p->curFlags & BTCF_Incrblob)!=0 ){
pBtree->hasIncrblobCur = 1;
if( isClearTable || p->info.nKey==iRow ){
p->eState = CURSOR_INVALID;
}
}
}
}
#else
/* Stub function when INCRBLOB is omitted */
#define invalidateIncrblobCursors(x,y,z)
#endif /* SQLITE_OMIT_INCRBLOB */
/*
** Set bit pgno of the BtShared.pHasContent bitvec. This is called
** when a page that previously contained data becomes a free-list leaf
** page.
**
** The BtShared.pHasContent bitvec exists to work around an obscure
** bug caused by the interaction of two useful IO optimizations surrounding
** free-list leaf pages:
**
** 1) When all data is deleted from a page and the page becomes
** a free-list leaf page, the page is not written to the database
** (as free-list leaf pages contain no meaningful data). Sometimes
** such a page is not even journalled (as it will not be modified,
** why bother journalling it?).
**
** 2) When a free-list leaf page is reused, its content is not read
** from the database or written to the journal file (why should it
** be, if it is not at all meaningful?).
**
** By themselves, these optimizations work fine and provide a handy
** performance boost to bulk delete or insert operations. However, if
** a page is moved to the free-list and then reused within the same
** transaction, a problem comes up. If the page is not journalled when
** it is moved to the free-list and it is also not journalled when it
** is extracted from the free-list and reused, then the original data
** may be lost. In the event of a rollback, it may not be possible
** to restore the database to its original configuration.
**
** The solution is the BtShared.pHasContent bitvec. Whenever a page is
** moved to become a free-list leaf page, the corresponding bit is
** set in the bitvec. Whenever a leaf page is extracted from the free-list,
** optimization 2 above is omitted if the corresponding bit is already
** set in BtShared.pHasContent. The contents of the bitvec are cleared
** at the end of every transaction.
*/
static int btreeSetHasContent(BtShared *pBt, Pgno pgno){
int rc = SQLITE_OK;
if( !pBt->pHasContent ){
assert( pgno<=pBt->nPage );
pBt->pHasContent = sqlite3BitvecCreate(pBt->nPage);
if( !pBt->pHasContent ){
rc = SQLITE_NOMEM_BKPT;
}
}
if( rc==SQLITE_OK && pgno<=sqlite3BitvecSize(pBt->pHasContent) ){
rc = sqlite3BitvecSet(pBt->pHasContent, pgno);
}
return rc;
}
/*
** Query the BtShared.pHasContent vector.
**
** This function is called when a free-list leaf page is removed from the
** free-list for reuse. It returns false if it is safe to retrieve the
** page from the pager layer with the 'no-content' flag set. True otherwise.
*/
static int btreeGetHasContent(BtShared *pBt, Pgno pgno){
Bitvec *p = pBt->pHasContent;
return (p && (pgno>sqlite3BitvecSize(p) || sqlite3BitvecTest(p, pgno)));
}
/*
** Clear (destroy) the BtShared.pHasContent bitvec. This should be
** invoked at the conclusion of each write-transaction.
*/
static void btreeClearHasContent(BtShared *pBt){
sqlite3BitvecDestroy(pBt->pHasContent);
pBt->pHasContent = 0;
}
/*
** Release all of the apPage[] pages for a cursor.
*/
static void btreeReleaseAllCursorPages(BtCursor *pCur){
int i;
for(i=0; i<=pCur->iPage; i++){
releasePage(pCur->apPage[i]);
pCur->apPage[i] = 0;
}
pCur->iPage = -1;
}
/*
** The cursor passed as the only argument must point to a valid entry
** when this function is called (i.e. have eState==CURSOR_VALID). This
** function saves the current cursor key in variables pCur->nKey and
** pCur->pKey. SQLITE_OK is returned if successful or an SQLite error
** code otherwise.
**
** If the cursor is open on an intkey table, then the integer key
** (the rowid) is stored in pCur->nKey and pCur->pKey is left set to
** NULL. If the cursor is open on a non-intkey table, then pCur->pKey is
** set to point to a malloced buffer pCur->nKey bytes in size containing
** the key.
*/
static int saveCursorKey(BtCursor *pCur){
int rc = SQLITE_OK;
assert( CURSOR_VALID==pCur->eState );
assert( 0==pCur->pKey );
assert( cursorHoldsMutex(pCur) );
if( pCur->curIntKey ){
/* Only the rowid is required for a table btree */
pCur->nKey = sqlite3BtreeIntegerKey(pCur);
}else{
/* For an index btree, save the complete key content */
void *pKey;
pCur->nKey = sqlite3BtreePayloadSize(pCur);
pKey = sqlite3Malloc( pCur->nKey );
if( pKey ){
rc = sqlite3BtreeKey(pCur, 0, (int)pCur->nKey, pKey);
if( rc==SQLITE_OK ){
pCur->pKey = pKey;
}else{
sqlite3_free(pKey);
}
}else{
rc = SQLITE_NOMEM_BKPT;
}
}
assert( !pCur->curIntKey || !pCur->pKey );
return rc;
}
/*
** Save the current cursor position in the variables BtCursor.nKey
** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
**
** The caller must ensure that the cursor is valid (has eState==CURSOR_VALID)
** prior to calling this routine.
*/
static int saveCursorPosition(BtCursor *pCur){
int rc;
assert( CURSOR_VALID==pCur->eState || CURSOR_SKIPNEXT==pCur->eState );
assert( 0==pCur->pKey );
assert( cursorHoldsMutex(pCur) );
if( pCur->eState==CURSOR_SKIPNEXT ){
pCur->eState = CURSOR_VALID;
}else{
pCur->skipNext = 0;
}
rc = saveCursorKey(pCur);
if( rc==SQLITE_OK ){
btreeReleaseAllCursorPages(pCur);
pCur->eState = CURSOR_REQUIRESEEK;
}
pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl|BTCF_AtLast);
return rc;
}
/* Forward reference */
static int SQLITE_NOINLINE saveCursorsOnList(BtCursor*,Pgno,BtCursor*);
/*
** Save the positions of all cursors (except pExcept) that are open on
** the table with root-page iRoot. "Saving the cursor position" means that
** the location in the btree is remembered in such a way that it can be
** moved back to the same spot after the btree has been modified. This
** routine is called just before cursor pExcept is used to modify the
** table, for example in BtreeDelete() or BtreeInsert().
**
** If there are two or more cursors on the same btree, then all such
** cursors should have their BTCF_Multiple flag set. The btreeCursor()
** routine enforces that rule. This routine only needs to be called in
** the uncommon case when pExpect has the BTCF_Multiple flag set.
**
** If pExpect!=NULL and if no other cursors are found on the same root-page,
** then the BTCF_Multiple flag on pExpect is cleared, to avoid another
** pointless call to this routine.
**
** Implementation note: This routine merely checks to see if any cursors
** need to be saved. It calls out to saveCursorsOnList() in the (unusual)
** event that cursors are in need to being saved.
*/
static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
BtCursor *p;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pExcept==0 || pExcept->pBt==pBt );
for(p=pBt->pCursor; p; p=p->pNext){
if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ) break;
}
if( p ) return saveCursorsOnList(p, iRoot, pExcept);
if( pExcept ) pExcept->curFlags &= ~BTCF_Multiple;
return SQLITE_OK;
}
/* This helper routine to saveAllCursors does the actual work of saving
** the cursors if and when a cursor is found that actually requires saving.
** The common case is that no cursors need to be saved, so this routine is
** broken out from its caller to avoid unnecessary stack pointer movement.
*/
static int SQLITE_NOINLINE saveCursorsOnList(
BtCursor *p, /* The first cursor that needs saving */
Pgno iRoot, /* Only save cursor with this iRoot. Save all if zero */
BtCursor *pExcept /* Do not save this cursor */
){
do{
if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ){
if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
int rc = saveCursorPosition(p);
if( SQLITE_OK!=rc ){
return rc;
}
}else{
testcase( p->iPage>0 );
btreeReleaseAllCursorPages(p);
}
}
p = p->pNext;
}while( p );
return SQLITE_OK;
}
/*
** Clear the current cursor position.
*/
void sqlite3BtreeClearCursor(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
sqlite3_free(pCur->pKey);
pCur->pKey = 0;
pCur->eState = CURSOR_INVALID;
}
/*
** In this version of BtreeMoveto, pKey is a packed index record
** such as is generated by the OP_MakeRecord opcode. Unpack the
** record and then call BtreeMovetoUnpacked() to do the work.
*/
static int btreeMoveto(
BtCursor *pCur, /* Cursor open on the btree to be searched */
const void *pKey, /* Packed key if the btree is an index */
i64 nKey, /* Integer key for tables. Size of pKey for indices */
int bias, /* Bias search to the high end */
int *pRes /* Write search results here */
){
int rc; /* Status code */
UnpackedRecord *pIdxKey; /* Unpacked index key */
char aSpace[384]; /* Temp space for pIdxKey - to avoid a malloc */
char *pFree = 0;
if( pKey ){
assert( nKey==(i64)(int)nKey );
pIdxKey = sqlite3VdbeAllocUnpackedRecord(
pCur->pKeyInfo, aSpace, sizeof(aSpace), &pFree
);
if( pIdxKey==0 ) return SQLITE_NOMEM_BKPT;
sqlite3VdbeRecordUnpack(pCur->pKeyInfo, (int)nKey, pKey, pIdxKey);
if( pIdxKey->nField==0 ){
sqlite3DbFree(pCur->pKeyInfo->db, pFree);
return SQLITE_CORRUPT_BKPT;
}
}else{
pIdxKey = 0;
}
rc = sqlite3BtreeMovetoUnpacked(pCur, pIdxKey, nKey, bias, pRes);
if( pFree ){
sqlite3DbFree(pCur->pKeyInfo->db, pFree);
}
return rc;
}
/*
** Restore the cursor to the position it was in (or as close to as possible)
** when saveCursorPosition() was called. Note that this call deletes the
** saved position info stored by saveCursorPosition(), so there can be
** at most one effective restoreCursorPosition() call after each
** saveCursorPosition().
*/
static int btreeRestoreCursorPosition(BtCursor *pCur){
int rc;
int skipNext;
assert( cursorOwnsBtShared(pCur) );
assert( pCur->eState>=CURSOR_REQUIRESEEK );
if( pCur->eState==CURSOR_FAULT ){
return pCur->skipNext;
}
pCur->eState = CURSOR_INVALID;
rc = btreeMoveto(pCur, pCur->pKey, pCur->nKey, 0, &skipNext);
if( rc==SQLITE_OK ){
sqlite3_free(pCur->pKey);
pCur->pKey = 0;
assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_INVALID );
pCur->skipNext |= skipNext;
if( pCur->skipNext && pCur->eState==CURSOR_VALID ){
pCur->eState = CURSOR_SKIPNEXT;
}
}
return rc;
}
#define restoreCursorPosition(p) \
(p->eState>=CURSOR_REQUIRESEEK ? \
btreeRestoreCursorPosition(p) : \
SQLITE_OK)
/*
** Determine whether or not a cursor has moved from the position where
** it was last placed, or has been invalidated for any other reason.
** Cursors can move when the row they are pointing at is deleted out
** from under them, for example. Cursor might also move if a btree
** is rebalanced.
**
** Calling this routine with a NULL cursor pointer returns false.
**
** Use the separate sqlite3BtreeCursorRestore() routine to restore a cursor
** back to where it ought to be if this routine returns true.
*/
int sqlite3BtreeCursorHasMoved(BtCursor *pCur){
return pCur->eState!=CURSOR_VALID;
}
/*
** This routine restores a cursor back to its original position after it
** has been moved by some outside activity (such as a btree rebalance or
** a row having been deleted out from under the cursor).
**
** On success, the *pDifferentRow parameter is false if the cursor is left
** pointing at exactly the same row. *pDifferntRow is the row the cursor
** was pointing to has been deleted, forcing the cursor to point to some
** nearby row.
**
** This routine should only be called for a cursor that just returned
** TRUE from sqlite3BtreeCursorHasMoved().
*/
int sqlite3BtreeCursorRestore(BtCursor *pCur, int *pDifferentRow){
int rc;
assert( pCur!=0 );
assert( pCur->eState!=CURSOR_VALID );
rc = restoreCursorPosition(pCur);
if( rc ){
*pDifferentRow = 1;
return rc;
}
if( pCur->eState!=CURSOR_VALID ){
*pDifferentRow = 1;
}else{
assert( pCur->skipNext==0 );
*pDifferentRow = 0;
}
return SQLITE_OK;
}
#ifdef SQLITE_ENABLE_CURSOR_HINTS
/*
** Provide hints to the cursor. The particular hint given (and the type
** and number of the varargs parameters) is determined by the eHintType
** parameter. See the definitions of the BTREE_HINT_* macros for details.
*/
void sqlite3BtreeCursorHint(BtCursor *pCur, int eHintType, ...){
/* Used only by system that substitute their own storage engine */
}
#endif
/*
** Provide flag hints to the cursor.
*/
void sqlite3BtreeCursorHintFlags(BtCursor *pCur, unsigned x){
assert( x==BTREE_SEEK_EQ || x==BTREE_BULKLOAD || x==0 );
pCur->hints = x;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Given a page number of a regular database page, return the page
** number for the pointer-map page that contains the entry for the
** input page number.
**
** Return 0 (not a valid page) for pgno==1 since there is
** no pointer map associated with page 1. The integrity_check logic
** requires that ptrmapPageno(*,1)!=1.
*/
static Pgno ptrmapPageno(BtShared *pBt, Pgno pgno){
int nPagesPerMapPage;
Pgno iPtrMap, ret;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pgno<2 ) return 0;
nPagesPerMapPage = (pBt->usableSize/5)+1;
iPtrMap = (pgno-2)/nPagesPerMapPage;
ret = (iPtrMap*nPagesPerMapPage) + 2;
if( ret==PENDING_BYTE_PAGE(pBt) ){
ret++;
}
return ret;
}
/*
** Write an entry into the pointer map.
**
** This routine updates the pointer map entry for page number 'key'
** so that it maps to type 'eType' and parent page number 'pgno'.
**
** If *pRC is initially non-zero (non-SQLITE_OK) then this routine is
** a no-op. If an error occurs, the appropriate error code is written
** into *pRC.
*/
static void ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent, int *pRC){
DbPage *pDbPage; /* The pointer map page */
u8 *pPtrmap; /* The pointer map data */
Pgno iPtrmap; /* The pointer map page number */
int offset; /* Offset in pointer map page */
int rc; /* Return code from subfunctions */
if( *pRC ) return;
assert( sqlite3_mutex_held(pBt->mutex) );
/* The master-journal page number must never be used as a pointer map page */
assert( 0==PTRMAP_ISPAGE(pBt, PENDING_BYTE_PAGE(pBt)) );
assert( pBt->autoVacuum );
if( key==0 ){
*pRC = SQLITE_CORRUPT_BKPT;
return;
}
iPtrmap = PTRMAP_PAGENO(pBt, key);
rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage, 0);
if( rc!=SQLITE_OK ){
*pRC = rc;
return;
}
offset = PTRMAP_PTROFFSET(iPtrmap, key);
if( offset<0 ){
*pRC = SQLITE_CORRUPT_BKPT;
goto ptrmap_exit;
}
assert( offset <= (int)pBt->usableSize-5 );
pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
if( eType!=pPtrmap[offset] || get4byte(&pPtrmap[offset+1])!=parent ){
TRACE(("PTRMAP_UPDATE: %d->(%d,%d)\n", key, eType, parent));
*pRC= rc = sqlite3PagerWrite(pDbPage);
if( rc==SQLITE_OK ){
pPtrmap[offset] = eType;
put4byte(&pPtrmap[offset+1], parent);
}
}
ptrmap_exit:
sqlite3PagerUnref(pDbPage);
}
/*
** Read an entry from the pointer map.
**
** This routine retrieves the pointer map entry for page 'key', writing
** the type and parent page number to *pEType and *pPgno respectively.
** An error code is returned if something goes wrong, otherwise SQLITE_OK.
*/
static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
DbPage *pDbPage; /* The pointer map page */
int iPtrmap; /* Pointer map page index */
u8 *pPtrmap; /* Pointer map page data */
int offset; /* Offset of entry in pointer map */
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
iPtrmap = PTRMAP_PAGENO(pBt, key);
rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage, 0);
if( rc!=0 ){
return rc;
}
pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
offset = PTRMAP_PTROFFSET(iPtrmap, key);
if( offset<0 ){
sqlite3PagerUnref(pDbPage);
return SQLITE_CORRUPT_BKPT;
}
assert( offset <= (int)pBt->usableSize-5 );
assert( pEType!=0 );
*pEType = pPtrmap[offset];
if( pPgno ) *pPgno = get4byte(&pPtrmap[offset+1]);
sqlite3PagerUnref(pDbPage);
if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_BKPT;
return SQLITE_OK;
}
#else /* if defined SQLITE_OMIT_AUTOVACUUM */
#define ptrmapPut(w,x,y,z,rc)
#define ptrmapGet(w,x,y,z) SQLITE_OK
#define ptrmapPutOvflPtr(x, y, rc)
#endif
/*
** Given a btree page and a cell index (0 means the first cell on
** the page, 1 means the second cell, and so forth) return a pointer
** to the cell content.
**
** findCellPastPtr() does the same except it skips past the initial
** 4-byte child pointer found on interior pages, if there is one.
**
** This routine works only for pages that do not contain overflow cells.
*/
#define findCell(P,I) \
((P)->aData + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
#define findCellPastPtr(P,I) \
((P)->aDataOfst + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
/*
** This is common tail processing for btreeParseCellPtr() and
** btreeParseCellPtrIndex() for the case when the cell does not fit entirely
** on a single B-tree page. Make necessary adjustments to the CellInfo
** structure.
*/
static SQLITE_NOINLINE void btreeParseCellAdjustSizeForOverflow(
MemPage *pPage, /* Page containing the cell */
u8 *pCell, /* Pointer to the cell text. */
CellInfo *pInfo /* Fill in this structure */
){
/* If the payload will not fit completely on the local page, we have
** to decide how much to store locally and how much to spill onto
** overflow pages. The strategy is to minimize the amount of unused
** space on overflow pages while keeping the amount of local storage
** in between minLocal and maxLocal.
**
** Warning: changing the way overflow payload is distributed in any
** way will result in an incompatible file format.
*/
int minLocal; /* Minimum amount of payload held locally */
int maxLocal; /* Maximum amount of payload held locally */
int surplus; /* Overflow payload available for local storage */
minLocal = pPage->minLocal;
maxLocal = pPage->maxLocal;
surplus = minLocal + (pInfo->nPayload - minLocal)%(pPage->pBt->usableSize-4);
testcase( surplus==maxLocal );
testcase( surplus==maxLocal+1 );
if( surplus <= maxLocal ){
pInfo->nLocal = (u16)surplus;
}else{
pInfo->nLocal = (u16)minLocal;
}
pInfo->nSize = (u16)(&pInfo->pPayload[pInfo->nLocal] - pCell) + 4;
}
/*
** The following routines are implementations of the MemPage.xParseCell()
** method.
**
** Parse a cell content block and fill in the CellInfo structure.
**
** btreeParseCellPtr() => table btree leaf nodes
** btreeParseCellNoPayload() => table btree internal nodes
** btreeParseCellPtrIndex() => index btree nodes
**
** There is also a wrapper function btreeParseCell() that works for
** all MemPage types and that references the cell by index rather than
** by pointer.
*/
static void btreeParseCellPtrNoPayload(
MemPage *pPage, /* Page containing the cell */
u8 *pCell, /* Pointer to the cell text. */
CellInfo *pInfo /* Fill in this structure */
){
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->leaf==0 );
assert( pPage->childPtrSize==4 );
#ifndef SQLITE_DEBUG
UNUSED_PARAMETER(pPage);
#endif
pInfo->nSize = 4 + getVarint(&pCell[4], (u64*)&pInfo->nKey);
pInfo->nPayload = 0;
pInfo->nLocal = 0;
pInfo->pPayload = 0;
return;
}
static void btreeParseCellPtr(
MemPage *pPage, /* Page containing the cell */
u8 *pCell, /* Pointer to the cell text. */
CellInfo *pInfo /* Fill in this structure */
){
u8 *pIter; /* For scanning through pCell */
u32 nPayload; /* Number of bytes of cell payload */
u64 iKey; /* Extracted Key value */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->leaf==0 || pPage->leaf==1 );
assert( pPage->intKeyLeaf );
assert( pPage->childPtrSize==0 );
pIter = pCell;
/* The next block of code is equivalent to:
**
** pIter += getVarint32(pIter, nPayload);
**
** The code is inlined to avoid a function call.
*/
nPayload = *pIter;
if( nPayload>=0x80 ){
u8 *pEnd = &pIter[8];
nPayload &= 0x7f;
do{
nPayload = (nPayload<<7) | (*++pIter & 0x7f);
}while( (*pIter)>=0x80 && pIter<pEnd );
}
pIter++;
/* The next block of code is equivalent to:
**
** pIter += getVarint(pIter, (u64*)&pInfo->nKey);
**
** The code is inlined to avoid a function call.
*/
iKey = *pIter;
if( iKey>=0x80 ){
u8 *pEnd = &pIter[7];
iKey &= 0x7f;
while(1){
iKey = (iKey<<7) | (*++pIter & 0x7f);
if( (*pIter)<0x80 ) break;
if( pIter>=pEnd ){
iKey = (iKey<<8) | *++pIter;
break;
}
}
}
pIter++;
pInfo->nKey = *(i64*)&iKey;
pInfo->nPayload = nPayload;
pInfo->pPayload = pIter;
testcase( nPayload==pPage->maxLocal );
testcase( nPayload==pPage->maxLocal+1 );
if( nPayload<=pPage->maxLocal ){
/* This is the (easy) common case where the entire payload fits
** on the local page. No overflow is required.
*/
pInfo->nSize = nPayload + (u16)(pIter - pCell);
if( pInfo->nSize<4 ) pInfo->nSize = 4;
pInfo->nLocal = (u16)nPayload;
}else{
btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
}
}
static void btreeParseCellPtrIndex(
MemPage *pPage, /* Page containing the cell */
u8 *pCell, /* Pointer to the cell text. */
CellInfo *pInfo /* Fill in this structure */
){
u8 *pIter; /* For scanning through pCell */
u32 nPayload; /* Number of bytes of cell payload */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->leaf==0 || pPage->leaf==1 );
assert( pPage->intKeyLeaf==0 );
pIter = pCell + pPage->childPtrSize;
nPayload = *pIter;
if( nPayload>=0x80 ){
u8 *pEnd = &pIter[8];
nPayload &= 0x7f;
do{
nPayload = (nPayload<<7) | (*++pIter & 0x7f);
}while( *(pIter)>=0x80 && pIter<pEnd );
}
pIter++;
pInfo->nKey = nPayload;
pInfo->nPayload = nPayload;
pInfo->pPayload = pIter;
testcase( nPayload==pPage->maxLocal );
testcase( nPayload==pPage->maxLocal+1 );
if( nPayload<=pPage->maxLocal ){
/* This is the (easy) common case where the entire payload fits
** on the local page. No overflow is required.
*/
pInfo->nSize = nPayload + (u16)(pIter - pCell);
if( pInfo->nSize<4 ) pInfo->nSize = 4;
pInfo->nLocal = (u16)nPayload;
}else{
btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
}
}
static void btreeParseCell(
MemPage *pPage, /* Page containing the cell */
int iCell, /* The cell index. First cell is 0 */
CellInfo *pInfo /* Fill in this structure */
){
pPage->xParseCell(pPage, findCell(pPage, iCell), pInfo);
}
/*
** The following routines are implementations of the MemPage.xCellSize
** method.
**
** Compute the total number of bytes that a Cell needs in the cell
** data area of the btree-page. The return number includes the cell
** data header and the local payload, but not any overflow page or
** the space used by the cell pointer.
**
** cellSizePtrNoPayload() => table internal nodes
** cellSizePtr() => all index nodes & table leaf nodes
*/
static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
u8 *pIter = pCell + pPage->childPtrSize; /* For looping over bytes of pCell */
u8 *pEnd; /* End mark for a varint */
u32 nSize; /* Size value to return */
#ifdef SQLITE_DEBUG
/* The value returned by this function should always be the same as
** the (CellInfo.nSize) value found by doing a full parse of the
** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
** this function verifies that this invariant is not violated. */
CellInfo debuginfo;
pPage->xParseCell(pPage, pCell, &debuginfo);
#endif
nSize = *pIter;
if( nSize>=0x80 ){
pEnd = &pIter[8];
nSize &= 0x7f;
do{
nSize = (nSize<<7) | (*++pIter & 0x7f);
}while( *(pIter)>=0x80 && pIter<pEnd );
}
pIter++;
if( pPage->intKey ){
/* pIter now points at the 64-bit integer key value, a variable length
** integer. The following block moves pIter to point at the first byte
** past the end of the key value. */
pEnd = &pIter[9];
while( (*pIter++)&0x80 && pIter<pEnd );
}
testcase( nSize==pPage->maxLocal );
testcase( nSize==pPage->maxLocal+1 );
if( nSize<=pPage->maxLocal ){
nSize += (u32)(pIter - pCell);
if( nSize<4 ) nSize = 4;
}else{
int minLocal = pPage->minLocal;
nSize = minLocal + (nSize - minLocal) % (pPage->pBt->usableSize - 4);
testcase( nSize==pPage->maxLocal );
testcase( nSize==pPage->maxLocal+1 );
if( nSize>pPage->maxLocal ){
nSize = minLocal;
}
nSize += 4 + (u16)(pIter - pCell);
}
assert( nSize==debuginfo.nSize || CORRUPT_DB );
return (u16)nSize;
}
static u16 cellSizePtrNoPayload(MemPage *pPage, u8 *pCell){
u8 *pIter = pCell + 4; /* For looping over bytes of pCell */
u8 *pEnd; /* End mark for a varint */
#ifdef SQLITE_DEBUG
/* The value returned by this function should always be the same as
** the (CellInfo.nSize) value found by doing a full parse of the
** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
** this function verifies that this invariant is not violated. */
CellInfo debuginfo;
pPage->xParseCell(pPage, pCell, &debuginfo);
#else
UNUSED_PARAMETER(pPage);
#endif
assert( pPage->childPtrSize==4 );
pEnd = pIter + 9;
while( (*pIter++)&0x80 && pIter<pEnd );
assert( debuginfo.nSize==(u16)(pIter - pCell) || CORRUPT_DB );
return (u16)(pIter - pCell);
}
#ifdef SQLITE_DEBUG
/* This variation on cellSizePtr() is used inside of assert() statements
** only. */
static u16 cellSize(MemPage *pPage, int iCell){
return pPage->xCellSize(pPage, findCell(pPage, iCell));
}
#endif
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** If the cell pCell, part of page pPage contains a pointer
** to an overflow page, insert an entry into the pointer-map
** for the overflow page.
*/
static void ptrmapPutOvflPtr(MemPage *pPage, u8 *pCell, int *pRC){
CellInfo info;
if( *pRC ) return;
assert( pCell!=0 );
pPage->xParseCell(pPage, pCell, &info);
if( info.nLocal<info.nPayload ){
Pgno ovfl = get4byte(&pCell[info.nSize-4]);
ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, pRC);
}
}
#endif
/*
** Defragment the page given. All Cells are moved to the
** end of the page and all free space is collected into one
** big FreeBlk that occurs in between the header and cell
** pointer array and the cell content area.
**
** EVIDENCE-OF: R-44582-60138 SQLite may from time to time reorganize a
** b-tree page so that there are no freeblocks or fragment bytes, all
** unused bytes are contained in the unallocated space region, and all
** cells are packed tightly at the end of the page.
*/
static int defragmentPage(MemPage *pPage){
int i; /* Loop counter */
int pc; /* Address of the i-th cell */
int hdr; /* Offset to the page header */
int size; /* Size of a cell */
int usableSize; /* Number of usable bytes on a page */
int cellOffset; /* Offset to the cell pointer array */
int cbrk; /* Offset to the cell content area */
int nCell; /* Number of cells on the page */
unsigned char *data; /* The page data */
unsigned char *temp; /* Temp area for cell content */
unsigned char *src; /* Source of content */
int iCellFirst; /* First allowable cell index */
int iCellLast; /* Last possible cell index */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt!=0 );
assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
assert( pPage->nOverflow==0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
temp = 0;
src = data = pPage->aData;
hdr = pPage->hdrOffset;
cellOffset = pPage->cellOffset;
nCell = pPage->nCell;
assert( nCell==get2byte(&data[hdr+3]) );
usableSize = pPage->pBt->usableSize;
cbrk = usableSize;
iCellFirst = cellOffset + 2*nCell;
iCellLast = usableSize - 4;
for(i=0; i<nCell; i++){
u8 *pAddr; /* The i-th cell pointer */
pAddr = &data[cellOffset + i*2];
pc = get2byte(pAddr);
testcase( pc==iCellFirst );
testcase( pc==iCellLast );
/* These conditions have already been verified in btreeInitPage()
** if PRAGMA cell_size_check=ON.
*/
if( pc<iCellFirst || pc>iCellLast ){
return SQLITE_CORRUPT_BKPT;
}
assert( pc>=iCellFirst && pc<=iCellLast );
size = pPage->xCellSize(pPage, &src[pc]);
cbrk -= size;
if( cbrk<iCellFirst || pc+size>usableSize ){
return SQLITE_CORRUPT_BKPT;
}
assert( cbrk+size<=usableSize && cbrk>=iCellFirst );
testcase( cbrk+size==usableSize );
testcase( pc+size==usableSize );
put2byte(pAddr, cbrk);
if( temp==0 ){
int x;
if( cbrk==pc ) continue;
temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
x = get2byte(&data[hdr+5]);
memcpy(&temp[x], &data[x], (cbrk+size) - x);
src = temp;
}
memcpy(&data[cbrk], &src[pc], size);
}
assert( cbrk>=iCellFirst );
put2byte(&data[hdr+5], cbrk);
data[hdr+1] = 0;
data[hdr+2] = 0;
data[hdr+7] = 0;
memset(&data[iCellFirst], 0, cbrk-iCellFirst);
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
if( cbrk-iCellFirst!=pPage->nFree ){
return SQLITE_CORRUPT_BKPT;
}
return SQLITE_OK;
}
/*
** Search the free-list on page pPg for space to store a cell nByte bytes in
** size. If one can be found, return a pointer to the space and remove it
** from the free-list.
**
** If no suitable space can be found on the free-list, return NULL.
**
** This function may detect corruption within pPg. If corruption is
** detected then *pRc is set to SQLITE_CORRUPT and NULL is returned.
**
** Slots on the free list that are between 1 and 3 bytes larger than nByte
** will be ignored if adding the extra space to the fragmentation count
** causes the fragmentation count to exceed 60.
*/
static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc){
const int hdr = pPg->hdrOffset;
u8 * const aData = pPg->aData;
int iAddr = hdr + 1;
int pc = get2byte(&aData[iAddr]);
int x;
int usableSize = pPg->pBt->usableSize;
assert( pc>0 );
do{
int size; /* Size of the free slot */
/* EVIDENCE-OF: R-06866-39125 Freeblocks are always connected in order of
** increasing offset. */
if( pc>usableSize-4 || pc<iAddr+4 ){
*pRc = SQLITE_CORRUPT_BKPT;
return 0;
}
/* EVIDENCE-OF: R-22710-53328 The third and fourth bytes of each
** freeblock form a big-endian integer which is the size of the freeblock
** in bytes, including the 4-byte header. */
size = get2byte(&aData[pc+2]);
if( (x = size - nByte)>=0 ){
testcase( x==4 );
testcase( x==3 );
if( pc < pPg->cellOffset+2*pPg->nCell || size+pc > usableSize ){
*pRc = SQLITE_CORRUPT_BKPT;
return 0;
}else if( x<4 ){
/* EVIDENCE-OF: R-11498-58022 In a well-formed b-tree page, the total
** number of bytes in fragments may not exceed 60. */
if( aData[hdr+7]>57 ) return 0;
/* Remove the slot from the free-list. Update the number of
** fragmented bytes within the page. */
memcpy(&aData[iAddr], &aData[pc], 2);
aData[hdr+7] += (u8)x;
}else{
/* The slot remains on the free-list. Reduce its size to account
** for the portion used by the new allocation. */
put2byte(&aData[pc+2], x);
}
return &aData[pc + x];
}
iAddr = pc;
pc = get2byte(&aData[pc]);
}while( pc );
return 0;
}
/*
** Allocate nByte bytes of space from within the B-Tree page passed
** as the first argument. Write into *pIdx the index into pPage->aData[]
** of the first byte of allocated space. Return either SQLITE_OK or
** an error code (usually SQLITE_CORRUPT).
**
** The caller guarantees that there is sufficient space to make the
** allocation. This routine might need to defragment in order to bring
** all the space together, however. This routine will avoid using
** the first two bytes past the cell pointer area since presumably this
** allocation is being made in order to insert a new cell, so we will
** also end up needing a new cell pointer.
*/
static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
const int hdr = pPage->hdrOffset; /* Local cache of pPage->hdrOffset */
u8 * const data = pPage->aData; /* Local cache of pPage->aData */
int top; /* First byte of cell content area */
int rc = SQLITE_OK; /* Integer return code */
int gap; /* First byte of gap between cell pointers and cell content */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( nByte>=0 ); /* Minimum cell size is 4 */
assert( pPage->nFree>=nByte );
assert( pPage->nOverflow==0 );
assert( nByte < (int)(pPage->pBt->usableSize-8) );
assert( pPage->cellOffset == hdr + 12 - 4*pPage->leaf );
gap = pPage->cellOffset + 2*pPage->nCell;
assert( gap<=65536 );
/* EVIDENCE-OF: R-29356-02391 If the database uses a 65536-byte page size
** and the reserved space is zero (the usual value for reserved space)
** then the cell content offset of an empty page wants to be 65536.
** However, that integer is too large to be stored in a 2-byte unsigned
** integer, so a value of 0 is used in its place. */
top = get2byte(&data[hdr+5]);
assert( top<=(int)pPage->pBt->usableSize ); /* Prevent by getAndInitPage() */
if( gap>top ){
if( top==0 && pPage->pBt->usableSize==65536 ){
top = 65536;
}else{
return SQLITE_CORRUPT_BKPT;
}
}
/* If there is enough space between gap and top for one more cell pointer
** array entry offset, and if the freelist is not empty, then search the
** freelist looking for a free slot big enough to satisfy the request.
*/
testcase( gap+2==top );
testcase( gap+1==top );
testcase( gap==top );
if( (data[hdr+2] || data[hdr+1]) && gap+2<=top ){
u8 *pSpace = pageFindSlot(pPage, nByte, &rc);
if( pSpace ){
assert( pSpace>=data && (pSpace - data)<65536 );
*pIdx = (int)(pSpace - data);
return SQLITE_OK;
}else if( rc ){
return rc;
}
}
/* The request could not be fulfilled using a freelist slot. Check
** to see if defragmentation is necessary.
*/
testcase( gap+2+nByte==top );
if( gap+2+nByte>top ){
assert( pPage->nCell>0 || CORRUPT_DB );
rc = defragmentPage(pPage);
if( rc ) return rc;
top = get2byteNotZero(&data[hdr+5]);
assert( gap+nByte<=top );
}
/* Allocate memory from the gap in between the cell pointer array
** and the cell content area. The btreeInitPage() call has already
** validated the freelist. Given that the freelist is valid, there
** is no way that the allocation can extend off the end of the page.
** The assert() below verifies the previous sentence.
*/
top -= nByte;
put2byte(&data[hdr+5], top);
assert( top+nByte <= (int)pPage->pBt->usableSize );
*pIdx = top;
return SQLITE_OK;
}
/*
** Return a section of the pPage->aData to the freelist.
** The first byte of the new free block is pPage->aData[iStart]
** and the size of the block is iSize bytes.
**
** Adjacent freeblocks are coalesced.
**
** Note that even though the freeblock list was checked by btreeInitPage(),
** that routine will not detect overlap between cells or freeblocks. Nor
** does it detect cells or freeblocks that encrouch into the reserved bytes
** at the end of the page. So do additional corruption checks inside this
** routine and return SQLITE_CORRUPT if any problems are found.
*/
static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
u16 iPtr; /* Address of ptr to next freeblock */
u16 iFreeBlk; /* Address of the next freeblock */
u8 hdr; /* Page header size. 0 or 100 */
u8 nFrag = 0; /* Reduction in fragmentation */
u16 iOrigSize = iSize; /* Original value of iSize */
u32 iLast = pPage->pBt->usableSize-4; /* Largest possible freeblock offset */
u32 iEnd = iStart + iSize; /* First byte past the iStart buffer */
unsigned char *data = pPage->aData; /* Page content */
assert( pPage->pBt!=0 );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( CORRUPT_DB || iStart>=pPage->hdrOffset+6+pPage->childPtrSize );
assert( CORRUPT_DB || iEnd <= pPage->pBt->usableSize );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( iSize>=4 ); /* Minimum cell size is 4 */
assert( iStart<=iLast );
/* Overwrite deleted information with zeros when the secure_delete
** option is enabled */
if( pPage->pBt->btsFlags & BTS_SECURE_DELETE ){
memset(&data[iStart], 0, iSize);
}
/* The list of freeblocks must be in ascending order. Find the
** spot on the list where iStart should be inserted.
*/
hdr = pPage->hdrOffset;
iPtr = hdr + 1;
if( data[iPtr+1]==0 && data[iPtr]==0 ){
iFreeBlk = 0; /* Shortcut for the case when the freelist is empty */
}else{
while( (iFreeBlk = get2byte(&data[iPtr]))<iStart ){
if( iFreeBlk<iPtr+4 ){
if( iFreeBlk==0 ) break;
return SQLITE_CORRUPT_BKPT;
}
iPtr = iFreeBlk;
}
if( iFreeBlk>iLast ) return SQLITE_CORRUPT_BKPT;
assert( iFreeBlk>iPtr || iFreeBlk==0 );
/* At this point:
** iFreeBlk: First freeblock after iStart, or zero if none
** iPtr: The address of a pointer to iFreeBlk
**
** Check to see if iFreeBlk should be coalesced onto the end of iStart.
*/
if( iFreeBlk && iEnd+3>=iFreeBlk ){
nFrag = iFreeBlk - iEnd;
if( iEnd>iFreeBlk ) return SQLITE_CORRUPT_BKPT;
iEnd = iFreeBlk + get2byte(&data[iFreeBlk+2]);
if( iEnd > pPage->pBt->usableSize ) return SQLITE_CORRUPT_BKPT;
iSize = iEnd - iStart;
iFreeBlk = get2byte(&data[iFreeBlk]);
}
/* If iPtr is another freeblock (that is, if iPtr is not the freelist
** pointer in the page header) then check to see if iStart should be
** coalesced onto the end of iPtr.
*/
if( iPtr>hdr+1 ){
int iPtrEnd = iPtr + get2byte(&data[iPtr+2]);
if( iPtrEnd+3>=iStart ){
if( iPtrEnd>iStart ) return SQLITE_CORRUPT_BKPT;
nFrag += iStart - iPtrEnd;
iSize = iEnd - iPtr;
iStart = iPtr;
}
}
if( nFrag>data[hdr+7] ) return SQLITE_CORRUPT_BKPT;
data[hdr+7] -= nFrag;
}
if( iStart==get2byte(&data[hdr+5]) ){
/* The new freeblock is at the beginning of the cell content area,
** so just extend the cell content area rather than create another
** freelist entry */
if( iPtr!=hdr+1 ) return SQLITE_CORRUPT_BKPT;
put2byte(&data[hdr+1], iFreeBlk);
put2byte(&data[hdr+5], iEnd);
}else{
/* Insert the new freeblock into the freelist */
put2byte(&data[iPtr], iStart);
put2byte(&data[iStart], iFreeBlk);
put2byte(&data[iStart+2], iSize);
}
pPage->nFree += iOrigSize;
return SQLITE_OK;
}
/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
**
** Only the following combinations are supported. Anything different
** indicates a corrupt database files:
**
** PTF_ZERODATA
** PTF_ZERODATA | PTF_LEAF
** PTF_LEAFDATA | PTF_INTKEY
** PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF
*/
static int decodeFlags(MemPage *pPage, int flagByte){
BtShared *pBt; /* A copy of pPage->pBt */
assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pPage->leaf = (u8)(flagByte>>3); assert( PTF_LEAF == 1<<3 );
flagByte &= ~PTF_LEAF;
pPage->childPtrSize = 4-4*pPage->leaf;
pPage->xCellSize = cellSizePtr;
pBt = pPage->pBt;
if( flagByte==(PTF_LEAFDATA | PTF_INTKEY) ){
/* EVIDENCE-OF: R-07291-35328 A value of 5 (0x05) means the page is an
** interior table b-tree page. */
assert( (PTF_LEAFDATA|PTF_INTKEY)==5 );
/* EVIDENCE-OF: R-26900-09176 A value of 13 (0x0d) means the page is a
** leaf table b-tree page. */
assert( (PTF_LEAFDATA|PTF_INTKEY|PTF_LEAF)==13 );
pPage->intKey = 1;
if( pPage->leaf ){
pPage->intKeyLeaf = 1;
pPage->xParseCell = btreeParseCellPtr;
}else{
pPage->intKeyLeaf = 0;
pPage->xCellSize = cellSizePtrNoPayload;
pPage->xParseCell = btreeParseCellPtrNoPayload;
}
pPage->maxLocal = pBt->maxLeaf;
pPage->minLocal = pBt->minLeaf;
}else if( flagByte==PTF_ZERODATA ){
/* EVIDENCE-OF: R-43316-37308 A value of 2 (0x02) means the page is an
** interior index b-tree page. */
assert( (PTF_ZERODATA)==2 );
/* EVIDENCE-OF: R-59615-42828 A value of 10 (0x0a) means the page is a
** leaf index b-tree page. */
assert( (PTF_ZERODATA|PTF_LEAF)==10 );
pPage->intKey = 0;
pPage->intKeyLeaf = 0;
pPage->xParseCell = btreeParseCellPtrIndex;
pPage->maxLocal = pBt->maxLocal;
pPage->minLocal = pBt->minLocal;
}else{
/* EVIDENCE-OF: R-47608-56469 Any other value for the b-tree page type is
** an error. */
return SQLITE_CORRUPT_BKPT;
}
pPage->max1bytePayload = pBt->max1bytePayload;
return SQLITE_OK;
}
/*
** Initialize the auxiliary information for a disk block.
**
** Return SQLITE_OK on success. If we see that the page does
** not contain a well-formed database page, then return
** SQLITE_CORRUPT. Note that a return of SQLITE_OK does not
** guarantee that the page is well-formed. It only shows that
** we failed to detect any corruption.
*/
static int btreeInitPage(MemPage *pPage){
assert( pPage->pBt!=0 );
assert( pPage->pBt->db!=0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) );
assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) );
if( !pPage->isInit ){
u16 pc; /* Address of a freeblock within pPage->aData[] */
u8 hdr; /* Offset to beginning of page header */
u8 *data; /* Equal to pPage->aData */
BtShared *pBt; /* The main btree structure */
int usableSize; /* Amount of usable space on each page */
u16 cellOffset; /* Offset from start of page to first cell pointer */
int nFree; /* Number of unused bytes on the page */
int top; /* First byte of the cell content area */
int iCellFirst; /* First allowable cell or freeblock offset */
int iCellLast; /* Last possible cell or freeblock offset */
pBt = pPage->pBt;
hdr = pPage->hdrOffset;
data = pPage->aData;
/* EVIDENCE-OF: R-28594-02890 The one-byte flag at offset 0 indicating
** the b-tree page type. */
if( decodeFlags(pPage, data[hdr]) ) return SQLITE_CORRUPT_BKPT;
assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
pPage->maskPage = (u16)(pBt->pageSize - 1);
pPage->nOverflow = 0;
usableSize = pBt->usableSize;
pPage->cellOffset = cellOffset = hdr + 8 + pPage->childPtrSize;
pPage->aDataEnd = &data[usableSize];
pPage->aCellIdx = &data[cellOffset];
pPage->aDataOfst = &data[pPage->childPtrSize];
/* EVIDENCE-OF: R-58015-48175 The two-byte integer at offset 5 designates
** the start of the cell content area. A zero value for this integer is
** interpreted as 65536. */
top = get2byteNotZero(&data[hdr+5]);
/* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
** number of cells on the page. */
pPage->nCell = get2byte(&data[hdr+3]);
if( pPage->nCell>MX_CELL(pBt) ){
/* To many cells for a single page. The page must be corrupt */
return SQLITE_CORRUPT_BKPT;
}
testcase( pPage->nCell==MX_CELL(pBt) );
/* EVIDENCE-OF: R-24089-57979 If a page contains no cells (which is only
** possible for a root page of a table that contains no rows) then the
** offset to the cell content area will equal the page size minus the
** bytes of reserved space. */
assert( pPage->nCell>0 || top==usableSize || CORRUPT_DB );
/* A malformed database page might cause us to read past the end
** of page when parsing a cell.
**
** The following block of code checks early to see if a cell extends
** past the end of a page boundary and causes SQLITE_CORRUPT to be
** returned if it does.
*/
iCellFirst = cellOffset + 2*pPage->nCell;
iCellLast = usableSize - 4;
if( pBt->db->flags & SQLITE_CellSizeCk ){
int i; /* Index into the cell pointer array */
int sz; /* Size of a cell */
if( !pPage->leaf ) iCellLast--;
for(i=0; i<pPage->nCell; i++){
pc = get2byteAligned(&data[cellOffset+i*2]);
testcase( pc==iCellFirst );
testcase( pc==iCellLast );
if( pc<iCellFirst || pc>iCellLast ){
return SQLITE_CORRUPT_BKPT;
}
sz = pPage->xCellSize(pPage, &data[pc]);
testcase( pc+sz==usableSize );
if( pc+sz>usableSize ){
return SQLITE_CORRUPT_BKPT;
}
}
if( !pPage->leaf ) iCellLast++;
}
/* Compute the total free space on the page
** EVIDENCE-OF: R-23588-34450 The two-byte integer at offset 1 gives the
** start of the first freeblock on the page, or is zero if there are no
** freeblocks. */
pc = get2byte(&data[hdr+1]);
nFree = data[hdr+7] + top; /* Init nFree to non-freeblock free space */
while( pc>0 ){
u16 next, size;
if( pc<iCellFirst || pc>iCellLast ){
/* EVIDENCE-OF: R-55530-52930 In a well-formed b-tree page, there will
** always be at least one cell before the first freeblock.
**
** Or, the freeblock is off the end of the page
*/
return SQLITE_CORRUPT_BKPT;
}
next = get2byte(&data[pc]);
size = get2byte(&data[pc+2]);
if( (next>0 && next<=pc+size+3) || pc+size>usableSize ){
/* Free blocks must be in ascending order. And the last byte of
** the free-block must lie on the database page. */
return SQLITE_CORRUPT_BKPT;
}
nFree = nFree + size;
pc = next;
}
/* At this point, nFree contains the sum of the offset to the start
** of the cell-content area plus the number of free bytes within
** the cell-content area. If this is greater than the usable-size
** of the page, then the page must be corrupted. This check also
** serves to verify that the offset to the start of the cell-content
** area, according to the page header, lies within the page.
*/
if( nFree>usableSize ){
return SQLITE_CORRUPT_BKPT;
}
pPage->nFree = (u16)(nFree - iCellFirst);
pPage->isInit = 1;
}
return SQLITE_OK;
}
/*
** Set up a raw page so that it looks like a database page holding
** no entries.
*/
static void zeroPage(MemPage *pPage, int flags){
unsigned char *data = pPage->aData;
BtShared *pBt = pPage->pBt;
u8 hdr = pPage->hdrOffset;
u16 first;
assert( sqlite3PagerPagenumber(pPage->pDbPage)==pPage->pgno );
assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
assert( sqlite3PagerGetData(pPage->pDbPage) == data );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( sqlite3_mutex_held(pBt->mutex) );
if( pBt->btsFlags & BTS_SECURE_DELETE ){
memset(&data[hdr], 0, pBt->usableSize - hdr);
}
data[hdr] = (char)flags;
first = hdr + ((flags&PTF_LEAF)==0 ? 12 : 8);
memset(&data[hdr+1], 0, 4);
data[hdr+7] = 0;
put2byte(&data[hdr+5], pBt->usableSize);
pPage->nFree = (u16)(pBt->usableSize - first);
decodeFlags(pPage, flags);
pPage->cellOffset = first;
pPage->aDataEnd = &data[pBt->usableSize];
pPage->aCellIdx = &data[first];
pPage->aDataOfst = &data[pPage->childPtrSize];
pPage->nOverflow = 0;
assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
pPage->maskPage = (u16)(pBt->pageSize - 1);
pPage->nCell = 0;
pPage->isInit = 1;
}
/*
** Convert a DbPage obtained from the pager into a MemPage used by
** the btree layer.
*/
static MemPage *btreePageFromDbPage(DbPage *pDbPage, Pgno pgno, BtShared *pBt){
MemPage *pPage = (MemPage*)sqlite3PagerGetExtra(pDbPage);
if( pgno!=pPage->pgno ){
pPage->aData = sqlite3PagerGetData(pDbPage);
pPage->pDbPage = pDbPage;
pPage->pBt = pBt;
pPage->pgno = pgno;
pPage->hdrOffset = pgno==1 ? 100 : 0;
}
assert( pPage->aData==sqlite3PagerGetData(pDbPage) );
return pPage;
}
/*
** Get a page from the pager. Initialize the MemPage.pBt and
** MemPage.aData elements if needed. See also: btreeGetUnusedPage().
**
** If the PAGER_GET_NOCONTENT flag is set, it means that we do not care
** about the content of the page at this time. So do not go to the disk
** to fetch the content. Just fill in the content with zeros for now.
** If in the future we call sqlite3PagerWrite() on this page, that
** means we have started to be concerned about content and the disk
** read should occur at that point.
*/
static int btreeGetPage(
BtShared *pBt, /* The btree */
Pgno pgno, /* Number of the page to fetch */
MemPage **ppPage, /* Return the page in this parameter */
int flags /* PAGER_GET_NOCONTENT or PAGER_GET_READONLY */
){
int rc;
DbPage *pDbPage;
assert( flags==0 || flags==PAGER_GET_NOCONTENT || flags==PAGER_GET_READONLY );
assert( sqlite3_mutex_held(pBt->mutex) );
rc = sqlite3PagerGet(pBt->pPager, pgno, (DbPage**)&pDbPage, flags);
if( rc ) return rc;
*ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
return SQLITE_OK;
}
/*
** Retrieve a page from the pager cache. If the requested page is not
** already in the pager cache return NULL. Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
*/
static MemPage *btreePageLookup(BtShared *pBt, Pgno pgno){
DbPage *pDbPage;
assert( sqlite3_mutex_held(pBt->mutex) );
pDbPage = sqlite3PagerLookup(pBt->pPager, pgno);
if( pDbPage ){
return btreePageFromDbPage(pDbPage, pgno, pBt);
}
return 0;
}
/*
** Return the size of the database file in pages. If there is any kind of
** error, return ((unsigned int)-1).
*/
static Pgno btreePagecount(BtShared *pBt){
return pBt->nPage;
}
u32 sqlite3BtreeLastPage(Btree *p){
assert( sqlite3BtreeHoldsMutex(p) );
assert( ((p->pBt->nPage)&0x8000000)==0 );
return btreePagecount(p->pBt);
}
/*
** Get a page from the pager and initialize it.
**
** If pCur!=0 then the page is being fetched as part of a moveToChild()
** call. Do additional sanity checking on the page in this case.
** And if the fetch fails, this routine must decrement pCur->iPage.
**
** The page is fetched as read-write unless pCur is not NULL and is
** a read-only cursor.
**
** If an error occurs, then *ppPage is undefined. It
** may remain unchanged, or it may be set to an invalid value.
*/
static int getAndInitPage(
BtShared *pBt, /* The database file */
Pgno pgno, /* Number of the page to get */
MemPage **ppPage, /* Write the page pointer here */
BtCursor *pCur, /* Cursor to receive the page, or NULL */
int bReadOnly /* True for a read-only page */
){
int rc;
DbPage *pDbPage;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pCur==0 || ppPage==&pCur->apPage[pCur->iPage] );
assert( pCur==0 || bReadOnly==pCur->curPagerFlags );
assert( pCur==0 || pCur->iPage>0 );
if( pgno>btreePagecount(pBt) ){
rc = SQLITE_CORRUPT_BKPT;
goto getAndInitPage_error;
}
rc = sqlite3PagerGet(pBt->pPager, pgno, (DbPage**)&pDbPage, bReadOnly);
if( rc ){
goto getAndInitPage_error;
}
*ppPage = (MemPage*)sqlite3PagerGetExtra(pDbPage);
if( (*ppPage)->isInit==0 ){
btreePageFromDbPage(pDbPage, pgno, pBt);
rc = btreeInitPage(*ppPage);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
goto getAndInitPage_error;
}
}
assert( (*ppPage)->pgno==pgno );
assert( (*ppPage)->aData==sqlite3PagerGetData(pDbPage) );
/* If obtaining a child page for a cursor, we must verify that the page is
** compatible with the root page. */
if( pCur && ((*ppPage)->nCell<1 || (*ppPage)->intKey!=pCur->curIntKey) ){
rc = SQLITE_CORRUPT_BKPT;
releasePage(*ppPage);
goto getAndInitPage_error;
}
return SQLITE_OK;
getAndInitPage_error:
if( pCur ) pCur->iPage--;
testcase( pgno==0 );
assert( pgno!=0 || rc==SQLITE_CORRUPT );
return rc;
}
/*
** Release a MemPage. This should be called once for each prior
** call to btreeGetPage.
*/
static void releasePageNotNull(MemPage *pPage){
assert( pPage->aData );
assert( pPage->pBt );
assert( pPage->pDbPage!=0 );
assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
sqlite3PagerUnrefNotNull(pPage->pDbPage);
}
static void releasePage(MemPage *pPage){
if( pPage ) releasePageNotNull(pPage);
}
/*
** Get an unused page.
**
** This works just like btreeGetPage() with the addition:
**
** * If the page is already in use for some other purpose, immediately
** release it and return an SQLITE_CURRUPT error.
** * Make sure the isInit flag is clear
*/
static int btreeGetUnusedPage(
BtShared *pBt, /* The btree */
Pgno pgno, /* Number of the page to fetch */
MemPage **ppPage, /* Return the page in this parameter */
int flags /* PAGER_GET_NOCONTENT or PAGER_GET_READONLY */
){
int rc = btreeGetPage(pBt, pgno, ppPage, flags);
if( rc==SQLITE_OK ){
if( sqlite3PagerPageRefcount((*ppPage)->pDbPage)>1 ){
releasePage(*ppPage);
*ppPage = 0;
return SQLITE_CORRUPT_BKPT;
}
(*ppPage)->isInit = 0;
}else{
*ppPage = 0;
}
return rc;
}
/*
** During a rollback, when the pager reloads information into the cache
** so that the cache is restored to its original state at the start of
** the transaction, for each page restored this routine is called.
**
** This routine needs to reset the extra data section at the end of the
** page to agree with the restored data.
*/
static void pageReinit(DbPage *pData){
MemPage *pPage;
pPage = (MemPage *)sqlite3PagerGetExtra(pData);
assert( sqlite3PagerPageRefcount(pData)>0 );
if( pPage->isInit ){
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pPage->isInit = 0;
if( sqlite3PagerPageRefcount(pData)>1 ){
/* pPage might not be a btree page; it might be an overflow page
** or ptrmap page or a free page. In those cases, the following
** call to btreeInitPage() will likely return SQLITE_CORRUPT.
** But no harm is done by this. And it is very important that
** btreeInitPage() be called on every btree page so we make
** the call for every page that comes in for re-initing. */
btreeInitPage(pPage);
}
}
}
/*
** Invoke the busy handler for a btree.
*/
static int btreeInvokeBusyHandler(void *pArg){
BtShared *pBt = (BtShared*)pArg;
assert( pBt->db );
assert( sqlite3_mutex_held(pBt->db->mutex) );
return sqlite3InvokeBusyHandler(&pBt->db->busyHandler);
}
/*
** Open a database file.
**
** zFilename is the name of the database file. If zFilename is NULL
** then an ephemeral database is created. The ephemeral database might
** be exclusively in memory, or it might use a disk-based memory cache.
** Either way, the ephemeral database will be automatically deleted
** when sqlite3BtreeClose() is called.
**
** If zFilename is ":memory:" then an in-memory database is created
** that is automatically destroyed when it is closed.
**
** The "flags" parameter is a bitmask that might contain bits like
** BTREE_OMIT_JOURNAL and/or BTREE_MEMORY.
**
** If the database is already opened in the same database connection
** and we are in shared cache mode, then the open will fail with an
** SQLITE_CONSTRAINT error. We cannot allow two or more BtShared
** objects in the same database connection since doing so will lead
** to problems with locking.
*/
int sqlite3BtreeOpen(
sqlite3_vfs *pVfs, /* VFS to use for this b-tree */
const char *zFilename, /* Name of the file containing the BTree database */
sqlite3 *db, /* Associated database handle */
Btree **ppBtree, /* Pointer to new Btree object written here */
int flags, /* Options */
int vfsFlags /* Flags passed through to sqlite3_vfs.xOpen() */
){
BtShared *pBt = 0; /* Shared part of btree structure */
Btree *p; /* Handle to return */
sqlite3_mutex *mutexOpen = 0; /* Prevents a race condition. Ticket #3537 */
int rc = SQLITE_OK; /* Result code from this function */
u8 nReserve; /* Byte of unused space on each page */
unsigned char zDbHeader[100]; /* Database header content */
/* True if opening an ephemeral, temporary database */
const int isTempDb = zFilename==0 || zFilename[0]==0;
/* Set the variable isMemdb to true for an in-memory database, or
** false for a file-based database.
*/
#ifdef SQLITE_OMIT_MEMORYDB
const int isMemdb = 0;
#else
const int isMemdb = (zFilename && strcmp(zFilename, ":memory:")==0)
|| (isTempDb && sqlite3TempInMemory(db))
|| (vfsFlags & SQLITE_OPEN_MEMORY)!=0;
#endif
assert( db!=0 );
assert( pVfs!=0 );
assert( sqlite3_mutex_held(db->mutex) );
assert( (flags&0xff)==flags ); /* flags fit in 8 bits */
/* Only a BTREE_SINGLE database can be BTREE_UNORDERED */
assert( (flags & BTREE_UNORDERED)==0 || (flags & BTREE_SINGLE)!=0 );
/* A BTREE_SINGLE database is always a temporary and/or ephemeral */
assert( (flags & BTREE_SINGLE)==0 || isTempDb );
if( isMemdb ){
flags |= BTREE_MEMORY;
}
if( (vfsFlags & SQLITE_OPEN_MAIN_DB)!=0 && (isMemdb || isTempDb) ){
vfsFlags = (vfsFlags & ~SQLITE_OPEN_MAIN_DB) | SQLITE_OPEN_TEMP_DB;
}
p = sqlite3MallocZero(sizeof(Btree));
if( !p ){
return SQLITE_NOMEM_BKPT;
}
p->inTrans = TRANS_NONE;
p->db = db;
#ifndef SQLITE_OMIT_SHARED_CACHE
p->lock.pBtree = p;
p->lock.iTable = 1;
#endif
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/*
** If this Btree is a candidate for shared cache, try to find an
** existing BtShared object that we can share with
*/
if( isTempDb==0 && (isMemdb==0 || (vfsFlags&SQLITE_OPEN_URI)!=0) ){
if( vfsFlags & SQLITE_OPEN_SHAREDCACHE ){
int nFilename = sqlite3Strlen30(zFilename)+1;
int nFullPathname = pVfs->mxPathname+1;
char *zFullPathname = sqlite3Malloc(MAX(nFullPathname,nFilename));
MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
p->sharable = 1;
if( !zFullPathname ){
sqlite3_free(p);
return SQLITE_NOMEM_BKPT;
}
if( isMemdb ){
memcpy(zFullPathname, zFilename, nFilename);
}else{
rc = sqlite3OsFullPathname(pVfs, zFilename,
nFullPathname, zFullPathname);
if( rc ){
sqlite3_free(zFullPathname);
sqlite3_free(p);
return rc;
}
}
#if SQLITE_THREADSAFE
mutexOpen = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_OPEN);
sqlite3_mutex_enter(mutexOpen);
mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
sqlite3_mutex_enter(mutexShared);
#endif
for(pBt=GLOBAL(BtShared*,sqlite3SharedCacheList); pBt; pBt=pBt->pNext){
assert( pBt->nRef>0 );
if( 0==strcmp(zFullPathname, sqlite3PagerFilename(pBt->pPager, 0))
&& sqlite3PagerVfs(pBt->pPager)==pVfs ){
int iDb;
for(iDb=db->nDb-1; iDb>=0; iDb--){
Btree *pExisting = db->aDb[iDb].pBt;
if( pExisting && pExisting->pBt==pBt ){
sqlite3_mutex_leave(mutexShared);
sqlite3_mutex_leave(mutexOpen);
sqlite3_free(zFullPathname);
sqlite3_free(p);
return SQLITE_CONSTRAINT;
}
}
p->pBt = pBt;
pBt->nRef++;
break;
}
}
sqlite3_mutex_leave(mutexShared);
sqlite3_free(zFullPathname);
}
#ifdef SQLITE_DEBUG
else{
/* In debug mode, we mark all persistent databases as sharable
** even when they are not. This exercises the locking code and
** gives more opportunity for asserts(sqlite3_mutex_held())
** statements to find locking problems.
*/
p->sharable = 1;
}
#endif
}
#endif
if( pBt==0 ){
/*
** The following asserts make sure that structures used by the btree are
** the right size. This is to guard against size changes that result
** when compiling on a different architecture.
*/
assert( sizeof(i64)==8 );
assert( sizeof(u64)==8 );
assert( sizeof(u32)==4 );
assert( sizeof(u16)==2 );
assert( sizeof(Pgno)==4 );
pBt = sqlite3MallocZero( sizeof(*pBt) );
if( pBt==0 ){
rc = SQLITE_NOMEM_BKPT;
goto btree_open_out;
}
rc = sqlite3PagerOpen(pVfs, &pBt->pPager, zFilename,
EXTRA_SIZE, flags, vfsFlags, pageReinit);
if( rc==SQLITE_OK ){
sqlite3PagerSetMmapLimit(pBt->pPager, db->szMmap);
rc = sqlite3PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
}
if( rc!=SQLITE_OK ){
goto btree_open_out;
}
pBt->openFlags = (u8)flags;
pBt->db = db;
sqlite3PagerSetBusyhandler(pBt->pPager, btreeInvokeBusyHandler, pBt);
p->pBt = pBt;
pBt->pCursor = 0;
pBt->pPage1 = 0;
if( sqlite3PagerIsreadonly(pBt->pPager) ) pBt->btsFlags |= BTS_READ_ONLY;
#ifdef SQLITE_SECURE_DELETE
pBt->btsFlags |= BTS_SECURE_DELETE;
#endif
/* EVIDENCE-OF: R-51873-39618 The page size for a database file is
** determined by the 2-byte integer located at an offset of 16 bytes from
** the beginning of the database file. */
pBt->pageSize = (zDbHeader[16]<<8) | (zDbHeader[17]<<16);
if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
|| ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
pBt->pageSize = 0;
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the magic name ":memory:" will create an in-memory database, then
** leave the autoVacuum mode at 0 (do not auto-vacuum), even if
** SQLITE_DEFAULT_AUTOVACUUM is true. On the other hand, if
** SQLITE_OMIT_MEMORYDB has been defined, then ":memory:" is just a
** regular file-name. In this case the auto-vacuum applies as per normal.
*/
if( zFilename && !isMemdb ){
pBt->autoVacuum = (SQLITE_DEFAULT_AUTOVACUUM ? 1 : 0);
pBt->incrVacuum = (SQLITE_DEFAULT_AUTOVACUUM==2 ? 1 : 0);
}
#endif
nReserve = 0;
}else{
/* EVIDENCE-OF: R-37497-42412 The size of the reserved region is
** determined by the one-byte unsigned integer found at an offset of 20
** into the database file header. */
nReserve = zDbHeader[20];
pBt->btsFlags |= BTS_PAGESIZE_FIXED;
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
pBt->incrVacuum = (get4byte(&zDbHeader[36 + 7*4])?1:0);
#endif
}
rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
if( rc ) goto btree_open_out;
pBt->usableSize = pBt->pageSize - nReserve;
assert( (pBt->pageSize & 7)==0 ); /* 8-byte alignment of pageSize */
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/* Add the new BtShared object to the linked list sharable BtShareds.
*/
pBt->nRef = 1;
if( p->sharable ){
MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
MUTEX_LOGIC( mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);)
if( SQLITE_THREADSAFE && sqlite3GlobalConfig.bCoreMutex ){
pBt->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_FAST);
if( pBt->mutex==0 ){
rc = SQLITE_NOMEM_BKPT;
goto btree_open_out;
}
}
sqlite3_mutex_enter(mutexShared);
pBt->pNext = GLOBAL(BtShared*,sqlite3SharedCacheList);
GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt;
sqlite3_mutex_leave(mutexShared);
}
#endif
}
#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
/* If the new Btree uses a sharable pBtShared, then link the new
** Btree into the list of all sharable Btrees for the same connection.
** The list is kept in ascending order by pBt address.
*/
if( p->sharable ){
int i;
Btree *pSib;
for(i=0; i<db->nDb; i++){
if( (pSib = db->aDb[i].pBt)!=0 && pSib->sharable ){
while( pSib->pPrev ){ pSib = pSib->pPrev; }
if( (uptr)p->pBt<(uptr)pSib->pBt ){
p->pNext = pSib;
p->pPrev = 0;
pSib->pPrev = p;
}else{
while( pSib->pNext && (uptr)pSib->pNext->pBt<(uptr)p->pBt ){
pSib = pSib->pNext;
}
p->pNext = pSib->pNext;
p->pPrev = pSib;
if( p->pNext ){
p->pNext->pPrev = p;
}
pSib->pNext = p;
}
break;
}
}
}
#endif
*ppBtree = p;
btree_open_out:
if( rc!=SQLITE_OK ){
if( pBt && pBt->pPager ){
sqlite3PagerClose(pBt->pPager);
}
sqlite3_free(pBt);
sqlite3_free(p);
*ppBtree = 0;
}else{
/* If the B-Tree was successfully opened, set the pager-cache size to the
** default value. Except, when opening on an existing shared pager-cache,
** do not change the pager-cache size.
*/
if( sqlite3BtreeSchema(p, 0, 0)==0 ){
sqlite3PagerSetCachesize(p->pBt->pPager, SQLITE_DEFAULT_CACHE_SIZE);
}
}
if( mutexOpen ){
assert( sqlite3_mutex_held(mutexOpen) );
sqlite3_mutex_leave(mutexOpen);
}
assert( rc!=SQLITE_OK || sqlite3BtreeConnectionCount(*ppBtree)>0 );
return rc;
}
/*
** Decrement the BtShared.nRef counter. When it reaches zero,
** remove the BtShared structure from the sharing list. Return
** true if the BtShared.nRef counter reaches zero and return
** false if it is still positive.
*/
static int removeFromSharingList(BtShared *pBt){
#ifndef SQLITE_OMIT_SHARED_CACHE
MUTEX_LOGIC( sqlite3_mutex *pMaster; )
BtShared *pList;
int removed = 0;
assert( sqlite3_mutex_notheld(pBt->mutex) );
MUTEX_LOGIC( pMaster = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
sqlite3_mutex_enter(pMaster);
pBt->nRef--;
if( pBt->nRef<=0 ){
if( GLOBAL(BtShared*,sqlite3SharedCacheList)==pBt ){
GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt->pNext;
}else{
pList = GLOBAL(BtShared*,sqlite3SharedCacheList);
while( ALWAYS(pList) && pList->pNext!=pBt ){
pList=pList->pNext;
}
if( ALWAYS(pList) ){
pList->pNext = pBt->pNext;
}
}
if( SQLITE_THREADSAFE ){
sqlite3_mutex_free(pBt->mutex);
}
removed = 1;
}
sqlite3_mutex_leave(pMaster);
return removed;
#else
return 1;
#endif
}
/*
** Make sure pBt->pTmpSpace points to an allocation of
** MX_CELL_SIZE(pBt) bytes with a 4-byte prefix for a left-child
** pointer.
*/
static void allocateTempSpace(BtShared *pBt){
if( !pBt->pTmpSpace ){
pBt->pTmpSpace = sqlite3PageMalloc( pBt->pageSize );
/* One of the uses of pBt->pTmpSpace is to format cells before
** inserting them into a leaf page (function fillInCell()). If
** a cell is less than 4 bytes in size, it is rounded up to 4 bytes
** by the various routines that manipulate binary cells. Which
** can mean that fillInCell() only initializes the first 2 or 3
** bytes of pTmpSpace, but that the first 4 bytes are copied from
** it into a database page. This is not actually a problem, but it
** does cause a valgrind error when the 1 or 2 bytes of unitialized
** data is passed to system call write(). So to avoid this error,
** zero the first 4 bytes of temp space here.
**
** Also: Provide four bytes of initialized space before the
** beginning of pTmpSpace as an area available to prepend the
** left-child pointer to the beginning of a cell.
*/
if( pBt->pTmpSpace ){
memset(pBt->pTmpSpace, 0, 8);
pBt->pTmpSpace += 4;
}
}
}
/*
** Free the pBt->pTmpSpace allocation
*/
static void freeTempSpace(BtShared *pBt){
if( pBt->pTmpSpace ){
pBt->pTmpSpace -= 4;
sqlite3PageFree(pBt->pTmpSpace);
pBt->pTmpSpace = 0;
}
}
/*
** Close an open database and invalidate all cursors.
*/
int sqlite3BtreeClose(Btree *p){
BtShared *pBt = p->pBt;
BtCursor *pCur;
/* Close all cursors opened via this handle. */
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
pCur = pBt->pCursor;
while( pCur ){
BtCursor *pTmp = pCur;
pCur = pCur->pNext;
if( pTmp->pBtree==p ){
sqlite3BtreeCloseCursor(pTmp);
}
}
/* Rollback any active transaction and free the handle structure.
** The call to sqlite3BtreeRollback() drops any table-locks held by
** this handle.
*/
sqlite3BtreeRollback(p, SQLITE_OK, 0);
sqlite3BtreeLeave(p);
/* If there are still other outstanding references to the shared-btree
** structure, return now. The remainder of this procedure cleans
** up the shared-btree.
*/
assert( p->wantToLock==0 && p->locked==0 );
if( !p->sharable || removeFromSharingList(pBt) ){
/* The pBt is no longer on the sharing list, so we can access
** it without having to hold the mutex.
**
** Clean out and delete the BtShared object.
*/
assert( !pBt->pCursor );
sqlite3PagerClose(pBt->pPager);
if( pBt->xFreeSchema && pBt->pSchema ){
pBt->xFreeSchema(pBt->pSchema);
}
sqlite3DbFree(0, pBt->pSchema);
freeTempSpace(pBt);
sqlite3_free(pBt);
}
#ifndef SQLITE_OMIT_SHARED_CACHE
assert( p->wantToLock==0 );
assert( p->locked==0 );
if( p->pPrev ) p->pPrev->pNext = p->pNext;
if( p->pNext ) p->pNext->pPrev = p->pPrev;
#endif
sqlite3_free(p);
return SQLITE_OK;
}
/*
** Change the "soft" limit on the number of pages in the cache.
** Unused and unmodified pages will be recycled when the number of
** pages in the cache exceeds this soft limit. But the size of the
** cache is allowed to grow larger than this limit if it contains
** dirty pages or pages still in active use.
*/
int sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetCachesize(pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
/*
** Change the "spill" limit on the number of pages in the cache.
** If the number of pages exceeds this limit during a write transaction,
** the pager might attempt to "spill" pages to the journal early in
** order to free up memory.
**
** The value returned is the current spill size. If zero is passed
** as an argument, no changes are made to the spill size setting, so
** using mxPage of 0 is a way to query the current spill size.
*/
int sqlite3BtreeSetSpillSize(Btree *p, int mxPage){
BtShared *pBt = p->pBt;
int res;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
res = sqlite3PagerSetSpillsize(pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return res;
}
#if SQLITE_MAX_MMAP_SIZE>0
/*
** Change the limit on the amount of the database file that may be
** memory mapped.
*/
int sqlite3BtreeSetMmapLimit(Btree *p, sqlite3_int64 szMmap){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetMmapLimit(pBt->pPager, szMmap);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
#endif /* SQLITE_MAX_MMAP_SIZE>0 */
/*
** Change the way data is synced to disk in order to increase or decrease
** how well the database resists damage due to OS crashes and power
** failures. Level 1 is the same as asynchronous (no syncs() occur and
** there is a high probability of damage) Level 2 is the default. There
** is a very low but non-zero probability of damage. Level 3 reduces the
** probability of damage to near zero but with a write performance reduction.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
int sqlite3BtreeSetPagerFlags(
Btree *p, /* The btree to set the safety level on */
unsigned pgFlags /* Various PAGER_* flags */
){
BtShared *pBt = p->pBt;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
sqlite3PagerSetFlags(pBt->pPager, pgFlags);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
#endif
/*
** Change the default pages size and the number of reserved bytes per page.
** Or, if the page size has already been fixed, return SQLITE_READONLY
** without changing anything.
**
** The page size must be a power of 2 between 512 and 65536. If the page
** size supplied does not meet this constraint then the page size is not
** changed.
**
** Page sizes are constrained to be a power of two so that the region
** of the database file used for locking (beginning at PENDING_BYTE,
** the first byte past the 1GB boundary, 0x40000000) needs to occur
** at the beginning of a page.
**
** If parameter nReserve is less than zero, then the number of reserved
** bytes per page is left unchanged.
**
** If the iFix!=0 then the BTS_PAGESIZE_FIXED flag is set so that the page size
** and autovacuum mode can no longer be changed.
*/
int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve, int iFix){
int rc = SQLITE_OK;
BtShared *pBt = p->pBt;
assert( nReserve>=-1 && nReserve<=255 );
sqlite3BtreeEnter(p);
#if SQLITE_HAS_CODEC
if( nReserve>pBt->optimalReserve ) pBt->optimalReserve = (u8)nReserve;
#endif
if( pBt->btsFlags & BTS_PAGESIZE_FIXED ){
sqlite3BtreeLeave(p);
return SQLITE_READONLY;
}
if( nReserve<0 ){
nReserve = pBt->pageSize - pBt->usableSize;
}
assert( nReserve>=0 && nReserve<=255 );
if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
((pageSize-1)&pageSize)==0 ){
assert( (pageSize & 7)==0 );
assert( !pBt->pCursor );
pBt->pageSize = (u32)pageSize;
freeTempSpace(pBt);
}
rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
pBt->usableSize = pBt->pageSize - (u16)nReserve;
if( iFix ) pBt->btsFlags |= BTS_PAGESIZE_FIXED;
sqlite3BtreeLeave(p);
return rc;
}
/*
** Return the currently defined page size
*/
int sqlite3BtreeGetPageSize(Btree *p){
return p->pBt->pageSize;
}
/*
** This function is similar to sqlite3BtreeGetReserve(), except that it
** may only be called if it is guaranteed that the b-tree mutex is already
** held.
**
** This is useful in one special case in the backup API code where it is
** known that the shared b-tree mutex is held, but the mutex on the
** database handle that owns *p is not. In this case if sqlite3BtreeEnter()
** were to be called, it might collide with some other operation on the
** database handle that owns *p, causing undefined behavior.
*/
int sqlite3BtreeGetReserveNoMutex(Btree *p){
int n;
assert( sqlite3_mutex_held(p->pBt->mutex) );
n = p->pBt->pageSize - p->pBt->usableSize;
return n;
}
/*
** Return the number of bytes of space at the end of every page that
** are intentually left unused. This is the "reserved" space that is
** sometimes used by extensions.
**
** If SQLITE_HAS_MUTEX is defined then the number returned is the
** greater of the current reserved space and the maximum requested
** reserve space.
*/
int sqlite3BtreeGetOptimalReserve(Btree *p){
int n;
sqlite3BtreeEnter(p);
n = sqlite3BtreeGetReserveNoMutex(p);
#ifdef SQLITE_HAS_CODEC
if( n<p->pBt->optimalReserve ) n = p->pBt->optimalReserve;
#endif
sqlite3BtreeLeave(p);
return n;
}
/*
** Set the maximum page count for a database if mxPage is positive.
** No changes are made if mxPage is 0 or negative.
** Regardless of the value of mxPage, return the maximum page count.
*/
int sqlite3BtreeMaxPageCount(Btree *p, int mxPage){
int n;
sqlite3BtreeEnter(p);
n = sqlite3PagerMaxPageCount(p->pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return n;
}
/*
** Set the BTS_SECURE_DELETE flag if newFlag is 0 or 1. If newFlag is -1,
** then make no changes. Always return the value of the BTS_SECURE_DELETE
** setting after the change.
*/
int sqlite3BtreeSecureDelete(Btree *p, int newFlag){
int b;
if( p==0 ) return 0;
sqlite3BtreeEnter(p);
if( newFlag>=0 ){
p->pBt->btsFlags &= ~BTS_SECURE_DELETE;
if( newFlag ) p->pBt->btsFlags |= BTS_SECURE_DELETE;
}
b = (p->pBt->btsFlags & BTS_SECURE_DELETE)!=0;
sqlite3BtreeLeave(p);
return b;
}
/*
** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it
** is disabled. The default value for the auto-vacuum property is
** determined by the SQLITE_DEFAULT_AUTOVACUUM macro.
*/
int sqlite3BtreeSetAutoVacuum(Btree *p, int autoVacuum){
#ifdef SQLITE_OMIT_AUTOVACUUM
return SQLITE_READONLY;
#else
BtShared *pBt = p->pBt;
int rc = SQLITE_OK;
u8 av = (u8)autoVacuum;
sqlite3BtreeEnter(p);
if( (pBt->btsFlags & BTS_PAGESIZE_FIXED)!=0 && (av ?1:0)!=pBt->autoVacuum ){
rc = SQLITE_READONLY;
}else{
pBt->autoVacuum = av ?1:0;
pBt->incrVacuum = av==2 ?1:0;
}
sqlite3BtreeLeave(p);
return rc;
#endif
}
/*
** Return the value of the 'auto-vacuum' property. If auto-vacuum is
** enabled 1 is returned. Otherwise 0.
*/
int sqlite3BtreeGetAutoVacuum(Btree *p){
#ifdef SQLITE_OMIT_AUTOVACUUM
return BTREE_AUTOVACUUM_NONE;
#else
int rc;
sqlite3BtreeEnter(p);
rc = (
(!p->pBt->autoVacuum)?BTREE_AUTOVACUUM_NONE:
(!p->pBt->incrVacuum)?BTREE_AUTOVACUUM_FULL:
BTREE_AUTOVACUUM_INCR
);
sqlite3BtreeLeave(p);
return rc;
#endif
}
/*
** Get a reference to pPage1 of the database file. This will
** also acquire a readlock on that file.
**
** SQLITE_OK is returned on success. If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked. SQLITE_NOMEM
** is returned if we run out of memory.
*/
static int lockBtree(BtShared *pBt){
int rc; /* Result code from subfunctions */
MemPage *pPage1; /* Page 1 of the database file */
int nPage; /* Number of pages in the database */
int nPageFile = 0; /* Number of pages in the database file */
int nPageHeader; /* Number of pages in the database according to hdr */
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pBt->pPage1==0 );
rc = sqlite3PagerSharedLock(pBt->pPager);
if( rc!=SQLITE_OK ) return rc;
rc = btreeGetPage(pBt, 1, &pPage1, 0);
if( rc!=SQLITE_OK ) return rc;
/* Do some checking to help insure the file we opened really is
** a valid database file.
*/
nPage = nPageHeader = get4byte(28+(u8*)pPage1->aData);
sqlite3PagerPagecount(pBt->pPager, &nPageFile);
if( nPage==0 || memcmp(24+(u8*)pPage1->aData, 92+(u8*)pPage1->aData,4)!=0 ){
nPage = nPageFile;
}
if( nPage>0 ){
u32 pageSize;
u32 usableSize;
u8 *page1 = pPage1->aData;
rc = SQLITE_NOTADB;
/* EVIDENCE-OF: R-43737-39999 Every valid SQLite database file begins
** with the following 16 bytes (in hex): 53 51 4c 69 74 65 20 66 6f 72 6d
** 61 74 20 33 00. */
if( memcmp(page1, zMagicHeader, 16)!=0 ){
goto page1_init_failed;
}
#ifdef SQLITE_OMIT_WAL
if( page1[18]>1 ){
pBt->btsFlags |= BTS_READ_ONLY;
}
if( page1[19]>1 ){
goto page1_init_failed;
}
#else
if( page1[18]>2 ){
pBt->btsFlags |= BTS_READ_ONLY;
}
if( page1[19]>2 ){
goto page1_init_failed;
}
/* If the write version is set to 2, this database should be accessed
** in WAL mode. If the log is not already open, open it now. Then
** return SQLITE_OK and return without populating BtShared.pPage1.
** The caller detects this and calls this function again. This is
** required as the version of page 1 currently in the page1 buffer
** may not be the latest version - there may be a newer one in the log
** file.
*/
if( page1[19]==2 && (pBt->btsFlags & BTS_NO_WAL)==0 ){
int isOpen = 0;
rc = sqlite3PagerOpenWal(pBt->pPager, &isOpen);
if( rc!=SQLITE_OK ){
goto page1_init_failed;
}else{
#if SQLITE_DEFAULT_SYNCHRONOUS!=SQLITE_DEFAULT_WAL_SYNCHRONOUS
sqlite3 *db;
Db *pDb;
if( (db=pBt->db)!=0 && (pDb=db->aDb)!=0 ){
while( pDb->pBt==0 || pDb->pBt->pBt!=pBt ){ pDb++; }
if( pDb->bSyncSet==0
&& pDb->safety_level==SQLITE_DEFAULT_SYNCHRONOUS+1
){
pDb->safety_level = SQLITE_DEFAULT_WAL_SYNCHRONOUS+1;
sqlite3PagerSetFlags(pBt->pPager,
pDb->safety_level | (db->flags & PAGER_FLAGS_MASK));
}
}
#endif
if( isOpen==0 ){
releasePage(pPage1);
return SQLITE_OK;
}
}
rc = SQLITE_NOTADB;
}
#endif
/* EVIDENCE-OF: R-15465-20813 The maximum and minimum embedded payload
** fractions and the leaf payload fraction values must be 64, 32, and 32.
**
** The original design allowed these amounts to vary, but as of
** version 3.6.0, we require them to be fixed.
*/
if( memcmp(&page1[21], "\100\040\040",3)!=0 ){
goto page1_init_failed;
}
/* EVIDENCE-OF: R-51873-39618 The page size for a database file is
** determined by the 2-byte integer located at an offset of 16 bytes from
** the beginning of the database file. */
pageSize = (page1[16]<<8) | (page1[17]<<16);
/* EVIDENCE-OF: R-25008-21688 The size of a page is a power of two
** between 512 and 65536 inclusive. */
if( ((pageSize-1)&pageSize)!=0
|| pageSize>SQLITE_MAX_PAGE_SIZE
|| pageSize<=256
){
goto page1_init_failed;
}
assert( (pageSize & 7)==0 );
/* EVIDENCE-OF: R-59310-51205 The "reserved space" size in the 1-byte
** integer at offset 20 is the number of bytes of space at the end of
** each page to reserve for extensions.
**
** EVIDENCE-OF: R-37497-42412 The size of the reserved region is
** determined by the one-byte unsigned integer found at an offset of 20
** into the database file header. */
usableSize = pageSize - page1[20];
if( (u32)pageSize!=pBt->pageSize ){
/* After reading the first page of the database assuming a page size
** of BtShared.pageSize, we have discovered that the page-size is
** actually pageSize. Unlock the database, leave pBt->pPage1 at
** zero and return SQLITE_OK. The caller will call this function
** again with the correct page-size.
*/
releasePage(pPage1);
pBt->usableSize = usableSize;
pBt->pageSize = pageSize;
freeTempSpace(pBt);
rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize,
pageSize-usableSize);
return rc;
}
if( (pBt->db->flags & SQLITE_RecoveryMode)==0 && nPage>nPageFile ){
rc = SQLITE_CORRUPT_BKPT;
goto page1_init_failed;
}
/* EVIDENCE-OF: R-28312-64704 However, the usable size is not allowed to
** be less than 480. In other words, if the page size is 512, then the
** reserved space size cannot exceed 32. */
if( usableSize<480 ){
goto page1_init_failed;
}
pBt->pageSize = pageSize;
pBt->usableSize = usableSize;
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->autoVacuum = (get4byte(&page1[36 + 4*4])?1:0);
pBt->incrVacuum = (get4byte(&page1[36 + 7*4])?1:0);
#endif
}
/* maxLocal is the maximum amount of payload to store locally for
** a cell. Make sure it is small enough so that at least minFanout
** cells can will fit on one page. We assume a 10-byte page header.
** Besides the payload, the cell must store:
** 2-byte pointer to the cell
** 4-byte child pointer
** 9-byte nKey value
** 4-byte nData value
** 4-byte overflow page pointer
** So a cell consists of a 2-byte pointer, a header which is as much as
** 17 bytes long, 0 to N bytes of payload, and an optional 4 byte overflow
** page pointer.
*/
pBt->maxLocal = (u16)((pBt->usableSize-12)*64/255 - 23);
pBt->minLocal = (u16)((pBt->usableSize-12)*32/255 - 23);
pBt->maxLeaf = (u16)(pBt->usableSize - 35);
pBt->minLeaf = (u16)((pBt->usableSize-12)*32/255 - 23);
if( pBt->maxLocal>127 ){
pBt->max1bytePayload = 127;
}else{
pBt->max1bytePayload = (u8)pBt->maxLocal;
}
assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE(pBt) );
pBt->pPage1 = pPage1;
pBt->nPage = nPage;
return SQLITE_OK;
page1_init_failed:
releasePage(pPage1);
pBt->pPage1 = 0;
return rc;
}
#ifndef NDEBUG
/*
** Return the number of cursors open on pBt. This is for use
** in assert() expressions, so it is only compiled if NDEBUG is not
** defined.
**
** Only write cursors are counted if wrOnly is true. If wrOnly is
** false then all cursors are counted.
**
** For the purposes of this routine, a cursor is any cursor that
** is capable of reading or writing to the database. Cursors that
** have been tripped into the CURSOR_FAULT state are not counted.
*/
static int countValidCursors(BtShared *pBt, int wrOnly){
BtCursor *pCur;
int r = 0;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( (wrOnly==0 || (pCur->curFlags & BTCF_WriteFlag)!=0)
&& pCur->eState!=CURSOR_FAULT ) r++;
}
return r;
}
#endif
/*
** If there are no outstanding cursors and we are not in the middle
** of a transaction but there is a read lock on the database, then
** this routine unrefs the first page of the database file which
** has the effect of releasing the read lock.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(BtShared *pBt){
assert( sqlite3_mutex_held(pBt->mutex) );
assert( countValidCursors(pBt,0)==0 || pBt->inTransaction>TRANS_NONE );
if( pBt->inTransaction==TRANS_NONE && pBt->pPage1!=0 ){
MemPage *pPage1 = pBt->pPage1;
assert( pPage1->aData );
assert( sqlite3PagerRefcount(pBt->pPager)==1 );
pBt->pPage1 = 0;
releasePageNotNull(pPage1);
}
}
/*
** If pBt points to an empty file then convert that empty file
** into a new empty database by initializing the first page of
** the database.
*/
static int newDatabase(BtShared *pBt){
MemPage *pP1;
unsigned char *data;
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pBt->nPage>0 ){
return SQLITE_OK;
}
pP1 = pBt->pPage1;
assert( pP1!=0 );
data = pP1->aData;
rc = sqlite3PagerWrite(pP1->pDbPage);
if( rc ) return rc;
memcpy(data, zMagicHeader, sizeof(zMagicHeader));
assert( sizeof(zMagicHeader)==16 );
data[16] = (u8)((pBt->pageSize>>8)&0xff);
data[17] = (u8)((pBt->pageSize>>16)&0xff);
data[18] = 1;
data[19] = 1;
assert( pBt->usableSize<=pBt->pageSize && pBt->usableSize+255>=pBt->pageSize);
data[20] = (u8)(pBt->pageSize - pBt->usableSize);
data[21] = 64;
data[22] = 32;
data[23] = 32;
memset(&data[24], 0, 100-24);
zeroPage(pP1, PTF_INTKEY|PTF_LEAF|PTF_LEAFDATA );
pBt->btsFlags |= BTS_PAGESIZE_FIXED;
#ifndef SQLITE_OMIT_AUTOVACUUM
assert( pBt->autoVacuum==1 || pBt->autoVacuum==0 );
assert( pBt->incrVacuum==1 || pBt->incrVacuum==0 );
put4byte(&data[36 + 4*4], pBt->autoVacuum);
put4byte(&data[36 + 7*4], pBt->incrVacuum);
#endif
pBt->nPage = 1;
data[31] = 1;
return SQLITE_OK;
}
/*
** Initialize the first page of the database file (creating a database
** consisting of a single page and no schema objects). Return SQLITE_OK
** if successful, or an SQLite error code otherwise.
*/
int sqlite3BtreeNewDb(Btree *p){
int rc;
sqlite3BtreeEnter(p);
p->pBt->nPage = 0;
rc = newDatabase(p->pBt);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Attempt to start a new transaction. A write-transaction
** is started if the second argument is nonzero, otherwise a read-
** transaction. If the second argument is 2 or more and exclusive
** transaction is started, meaning that no other process is allowed
** to access the database. A preexisting transaction may not be
** upgraded to exclusive by calling this routine a second time - the
** exclusivity flag only works for a new transaction.
**
** A write-transaction must be started before attempting any
** changes to the database. None of the following routines
** will work unless a transaction is started first:
**
** sqlite3BtreeCreateTable()
** sqlite3BtreeCreateIndex()
** sqlite3BtreeClearTable()
** sqlite3BtreeDropTable()
** sqlite3BtreeInsert()
** sqlite3BtreeDelete()
** sqlite3BtreeUpdateMeta()
**
** If an initial attempt to acquire the lock fails because of lock contention
** and the database was previously unlocked, then invoke the busy handler
** if there is one. But if there was previously a read-lock, do not
** invoke the busy handler - just return SQLITE_BUSY. SQLITE_BUSY is
** returned when there is already a read-lock in order to avoid a deadlock.
**
** Suppose there are two processes A and B. A has a read lock and B has
** a reserved lock. B tries to promote to exclusive but is blocked because
** of A's read lock. A tries to promote to reserved but is blocked by B.
** One or the other of the two processes must give way or there can be
** no progress. By returning SQLITE_BUSY and not invoking the busy callback
** when A already has a read lock, we encourage A to give up and let B
** proceed.
*/
int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
BtShared *pBt = p->pBt;
int rc = SQLITE_OK;
sqlite3BtreeEnter(p);
btreeIntegrity(p);
/* If the btree is already in a write-transaction, or it
** is already in a read-transaction and a read-transaction
** is requested, this is a no-op.
*/
if( p->inTrans==TRANS_WRITE || (p->inTrans==TRANS_READ && !wrflag) ){
goto trans_begun;
}
assert( pBt->inTransaction==TRANS_WRITE || IfNotOmitAV(pBt->bDoTruncate)==0 );
/* Write transactions are not possible on a read-only database */
if( (pBt->btsFlags & BTS_READ_ONLY)!=0 && wrflag ){
rc = SQLITE_READONLY;
goto trans_begun;
}
#ifndef SQLITE_OMIT_SHARED_CACHE
{
sqlite3 *pBlock = 0;
/* If another database handle has already opened a write transaction
** on this shared-btree structure and a second write transaction is
** requested, return SQLITE_LOCKED.
*/
if( (wrflag && pBt->inTransaction==TRANS_WRITE)
|| (pBt->btsFlags & BTS_PENDING)!=0
){
pBlock = pBt->pWriter->db;
}else if( wrflag>1 ){
BtLock *pIter;
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->pBtree!=p ){
pBlock = pIter->pBtree->db;
break;
}
}
}
if( pBlock ){
sqlite3ConnectionBlocked(p->db, pBlock);
rc = SQLITE_LOCKED_SHAREDCACHE;
goto trans_begun;
}
}
#endif
/* Any read-only or read-write transaction implies a read-lock on
** page 1. So if some other shared-cache client already has a write-lock
** on page 1, the transaction cannot be opened. */
rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);
if( SQLITE_OK!=rc ) goto trans_begun;
pBt->btsFlags &= ~BTS_INITIALLY_EMPTY;
if( pBt->nPage==0 ) pBt->btsFlags |= BTS_INITIALLY_EMPTY;
do {
/* Call lockBtree() until either pBt->pPage1 is populated or
** lockBtree() returns something other than SQLITE_OK. lockBtree()
** may return SQLITE_OK but leave pBt->pPage1 set to 0 if after
** reading page 1 it discovers that the page-size of the database
** file is not pBt->pageSize. In this case lockBtree() will update
** pBt->pageSize to the page-size of the file on disk.
*/
while( pBt->pPage1==0 && SQLITE_OK==(rc = lockBtree(pBt)) );
if( rc==SQLITE_OK && wrflag ){
if( (pBt->btsFlags & BTS_READ_ONLY)!=0 ){
rc = SQLITE_READONLY;
}else{
rc = sqlite3PagerBegin(pBt->pPager,wrflag>1,sqlite3TempInMemory(p->db));
if( rc==SQLITE_OK ){
rc = newDatabase(pBt);
}
}
}
if( rc!=SQLITE_OK ){
unlockBtreeIfUnused(pBt);
}
}while( (rc&0xFF)==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
btreeInvokeBusyHandler(pBt) );
if( rc==SQLITE_OK ){
if( p->inTrans==TRANS_NONE ){
pBt->nTransaction++;
#ifndef SQLITE_OMIT_SHARED_CACHE
if( p->sharable ){
assert( p->lock.pBtree==p && p->lock.iTable==1 );
p->lock.eLock = READ_LOCK;
p->lock.pNext = pBt->pLock;
pBt->pLock = &p->lock;
}
#endif
}
p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
if( p->inTrans>pBt->inTransaction ){
pBt->inTransaction = p->inTrans;
}
if( wrflag ){
MemPage *pPage1 = pBt->pPage1;
#ifndef SQLITE_OMIT_SHARED_CACHE
assert( !pBt->pWriter );
pBt->pWriter = p;
pBt->btsFlags &= ~BTS_EXCLUSIVE;
if( wrflag>1 ) pBt->btsFlags |= BTS_EXCLUSIVE;
#endif
/* If the db-size header field is incorrect (as it may be if an old
** client has been writing the database file), update it now. Doing
** this sooner rather than later means the database size can safely
** re-read the database size from page 1 if a savepoint or transaction
** rollback occurs within the transaction.
*/
if( pBt->nPage!=get4byte(&pPage1->aData[28]) ){
rc = sqlite3PagerWrite(pPage1->pDbPage);
if( rc==SQLITE_OK ){
put4byte(&pPage1->aData[28], pBt->nPage);
}
}
}
}
trans_begun:
if( rc==SQLITE_OK && wrflag ){
/* This call makes sure that the pager has the correct number of
** open savepoints. If the second parameter is greater than 0 and
** the sub-journal is not already open, then it will be opened here.
*/
rc = sqlite3PagerOpenSavepoint(pBt->pPager, p->db->nSavepoint);
}
btreeIntegrity(p);
sqlite3BtreeLeave(p);
return rc;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Set the pointer-map entries for all children of page pPage. Also, if
** pPage contains cells that point to overflow pages, set the pointer
** map entries for the overflow pages as well.
*/
static int setChildPtrmaps(MemPage *pPage){
int i; /* Counter variable */
int nCell; /* Number of cells in page pPage */
int rc; /* Return code */
BtShared *pBt = pPage->pBt;
u8 isInitOrig = pPage->isInit;
Pgno pgno = pPage->pgno;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
rc = btreeInitPage(pPage);
if( rc!=SQLITE_OK ){
goto set_child_ptrmaps_out;
}
nCell = pPage->nCell;
for(i=0; i<nCell; i++){
u8 *pCell = findCell(pPage, i);
ptrmapPutOvflPtr(pPage, pCell, &rc);
if( !pPage->leaf ){
Pgno childPgno = get4byte(pCell);
ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
}
}
if( !pPage->leaf ){
Pgno childPgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
}
set_child_ptrmaps_out:
pPage->isInit = isInitOrig;
return rc;
}
/*
** Somewhere on pPage is a pointer to page iFrom. Modify this pointer so
** that it points to iTo. Parameter eType describes the type of pointer to
** be modified, as follows:
**
** PTRMAP_BTREE: pPage is a btree-page. The pointer points at a child
** page of pPage.
**
** PTRMAP_OVERFLOW1: pPage is a btree-page. The pointer points at an overflow
** page pointed to by one of the cells on pPage.
**
** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
** overflow page in the list.
*/
static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
if( eType==PTRMAP_OVERFLOW2 ){
/* The pointer is always the first 4 bytes of the page in this case. */
if( get4byte(pPage->aData)!=iFrom ){
return SQLITE_CORRUPT_BKPT;
}
put4byte(pPage->aData, iTo);
}else{
u8 isInitOrig = pPage->isInit;
int i;
int nCell;
int rc;
rc = btreeInitPage(pPage);
if( rc ) return rc;
nCell = pPage->nCell;
for(i=0; i<nCell; i++){
u8 *pCell = findCell(pPage, i);
if( eType==PTRMAP_OVERFLOW1 ){
CellInfo info;
pPage->xParseCell(pPage, pCell, &info);
if( info.nLocal<info.nPayload
&& pCell+info.nSize-1<=pPage->aData+pPage->maskPage
&& iFrom==get4byte(pCell+info.nSize-4)
){
put4byte(pCell+info.nSize-4, iTo);
break;
}
}else{
if( get4byte(pCell)==iFrom ){
put4byte(pCell, iTo);
break;
}
}
}
if( i==nCell ){
if( eType!=PTRMAP_BTREE ||
get4byte(&pPage->aData[pPage->hdrOffset+8])!=iFrom ){
return SQLITE_CORRUPT_BKPT;
}
put4byte(&pPage->aData[pPage->hdrOffset+8], iTo);
}
pPage->isInit = isInitOrig;
}
return SQLITE_OK;
}
/*
** Move the open database page pDbPage to location iFreePage in the
** database. The pDbPage reference remains valid.
**
** The isCommit flag indicates that there is no need to remember that
** the journal needs to be sync()ed before database page pDbPage->pgno
** can be written to. The caller has already promised not to write to that
** page.
*/
static int relocatePage(
BtShared *pBt, /* Btree */
MemPage *pDbPage, /* Open page to move */
u8 eType, /* Pointer map 'type' entry for pDbPage */
Pgno iPtrPage, /* Pointer map 'page-no' entry for pDbPage */
Pgno iFreePage, /* The location to move pDbPage to */
int isCommit /* isCommit flag passed to sqlite3PagerMovepage */
){
MemPage *pPtrPage; /* The page that contains a pointer to pDbPage */
Pgno iDbPage = pDbPage->pgno;
Pager *pPager = pBt->pPager;
int rc;
assert( eType==PTRMAP_OVERFLOW2 || eType==PTRMAP_OVERFLOW1 ||
eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE );
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pDbPage->pBt==pBt );
/* Move page iDbPage from its current location to page number iFreePage */
TRACE(("AUTOVACUUM: Moving %d to free page %d (ptr page %d type %d)\n",
iDbPage, iFreePage, iPtrPage, eType));
rc = sqlite3PagerMovepage(pPager, pDbPage->pDbPage, iFreePage, isCommit);
if( rc!=SQLITE_OK ){
return rc;
}
pDbPage->pgno = iFreePage;
/* If pDbPage was a btree-page, then it may have child pages and/or cells
** that point to overflow pages. The pointer map entries for all these
** pages need to be changed.
**
** If pDbPage is an overflow page, then the first 4 bytes may store a
** pointer to a subsequent overflow page. If this is the case, then
** the pointer map needs to be updated for the subsequent overflow page.
*/
if( eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE ){
rc = setChildPtrmaps(pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
}else{
Pgno nextOvfl = get4byte(pDbPage->aData);
if( nextOvfl!=0 ){
ptrmapPut(pBt, nextOvfl, PTRMAP_OVERFLOW2, iFreePage, &rc);
if( rc!=SQLITE_OK ){
return rc;
}
}
}
/* Fix the database pointer on page iPtrPage that pointed at iDbPage so
** that it points at iFreePage. Also fix the pointer map entry for
** iPtrPage.
*/
if( eType!=PTRMAP_ROOTPAGE ){
rc = btreeGetPage(pBt, iPtrPage, &pPtrPage, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pPtrPage->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pPtrPage);
return rc;
}
rc = modifyPagePointer(pPtrPage, iDbPage, iFreePage, eType);
releasePage(pPtrPage);
if( rc==SQLITE_OK ){
ptrmapPut(pBt, iFreePage, eType, iPtrPage, &rc);
}
}
return rc;
}
/* Forward declaration required by incrVacuumStep(). */
static int allocateBtreePage(BtShared *, MemPage **, Pgno *, Pgno, u8);
/*
** Perform a single step of an incremental-vacuum. If successful, return
** SQLITE_OK. If there is no work to do (and therefore no point in
** calling this function again), return SQLITE_DONE. Or, if an error
** occurs, return some other error code.
**
** More specifically, this function attempts to re-organize the database so
** that the last page of the file currently in use is no longer in use.
**
** Parameter nFin is the number of pages that this database would contain
** were this function called until it returns SQLITE_DONE.
**
** If the bCommit parameter is non-zero, this function assumes that the
** caller will keep calling incrVacuumStep() until it returns SQLITE_DONE
** or an error. bCommit is passed true for an auto-vacuum-on-commit
** operation, or false for an incremental vacuum.
*/
static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg, int bCommit){
Pgno nFreeList; /* Number of pages still on the free-list */
int rc;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( iLastPg>nFin );
if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
u8 eType;
Pgno iPtrPage;
nFreeList = get4byte(&pBt->pPage1->aData[36]);
if( nFreeList==0 ){
return SQLITE_DONE;
}
rc = ptrmapGet(pBt, iLastPg, &eType, &iPtrPage);
if( rc!=SQLITE_OK ){
return rc;
}
if( eType==PTRMAP_ROOTPAGE ){
return SQLITE_CORRUPT_BKPT;
}
if( eType==PTRMAP_FREEPAGE ){
if( bCommit==0 ){
/* Remove the page from the files free-list. This is not required
** if bCommit is non-zero. In that case, the free-list will be
** truncated to zero after this function returns, so it doesn't
** matter if it still contains some garbage entries.
*/
Pgno iFreePg;
MemPage *pFreePg;
rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iLastPg, BTALLOC_EXACT);
if( rc!=SQLITE_OK ){
return rc;
}
assert( iFreePg==iLastPg );
releasePage(pFreePg);
}
} else {
Pgno iFreePg; /* Index of free page to move pLastPg to */
MemPage *pLastPg;
u8 eMode = BTALLOC_ANY; /* Mode parameter for allocateBtreePage() */
Pgno iNear = 0; /* nearby parameter for allocateBtreePage() */
rc = btreeGetPage(pBt, iLastPg, &pLastPg, 0);
if( rc!=SQLITE_OK ){
return rc;
}
/* If bCommit is zero, this loop runs exactly once and page pLastPg
** is swapped with the first free page pulled off the free list.
**
** On the other hand, if bCommit is greater than zero, then keep
** looping until a free-page located within the first nFin pages
** of the file is found.
*/
if( bCommit==0 ){
eMode = BTALLOC_LE;
iNear = nFin;
}
do {
MemPage *pFreePg;
rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iNear, eMode);
if( rc!=SQLITE_OK ){
releasePage(pLastPg);
return rc;
}
releasePage(pFreePg);
}while( bCommit && iFreePg>nFin );
assert( iFreePg<iLastPg );
rc = relocatePage(pBt, pLastPg, eType, iPtrPage, iFreePg, bCommit);
releasePage(pLastPg);
if( rc!=SQLITE_OK ){
return rc;
}
}
}
if( bCommit==0 ){
do {
iLastPg--;
}while( iLastPg==PENDING_BYTE_PAGE(pBt) || PTRMAP_ISPAGE(pBt, iLastPg) );
pBt->bDoTruncate = 1;
pBt->nPage = iLastPg;
}
return SQLITE_OK;
}
/*
** The database opened by the first argument is an auto-vacuum database
** nOrig pages in size containing nFree free pages. Return the expected
** size of the database in pages following an auto-vacuum operation.
*/
static Pgno finalDbSize(BtShared *pBt, Pgno nOrig, Pgno nFree){
int nEntry; /* Number of entries on one ptrmap page */
Pgno nPtrmap; /* Number of PtrMap pages to be freed */
Pgno nFin; /* Return value */
nEntry = pBt->usableSize/5;
nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+nEntry)/nEntry;
nFin = nOrig - nFree - nPtrmap;
if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<PENDING_BYTE_PAGE(pBt) ){
nFin--;
}
while( PTRMAP_ISPAGE(pBt, nFin) || nFin==PENDING_BYTE_PAGE(pBt) ){
nFin--;
}
return nFin;
}
/*
** A write-transaction must be opened before calling this function.
** It performs a single unit of work towards an incremental vacuum.
**
** If the incremental vacuum is finished after this function has run,
** SQLITE_DONE is returned. If it is not finished, but no error occurred,
** SQLITE_OK is returned. Otherwise an SQLite error code.
*/
int sqlite3BtreeIncrVacuum(Btree *p){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
assert( pBt->inTransaction==TRANS_WRITE && p->inTrans==TRANS_WRITE );
if( !pBt->autoVacuum ){
rc = SQLITE_DONE;
}else{
Pgno nOrig = btreePagecount(pBt);
Pgno nFree = get4byte(&pBt->pPage1->aData[36]);
Pgno nFin = finalDbSize(pBt, nOrig, nFree);
if( nOrig<nFin ){
rc = SQLITE_CORRUPT_BKPT;
}else if( nFree>0 ){
rc = saveAllCursors(pBt, 0, 0);
if( rc==SQLITE_OK ){
invalidateAllOverflowCache(pBt);
rc = incrVacuumStep(pBt, nFin, nOrig, 0);
}
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
put4byte(&pBt->pPage1->aData[28], pBt->nPage);
}
}else{
rc = SQLITE_DONE;
}
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** This routine is called prior to sqlite3PagerCommit when a transaction
** is committed for an auto-vacuum database.
**
** If SQLITE_OK is returned, then *pnTrunc is set to the number of pages
** the database file should be truncated to during the commit process.
** i.e. the database has been reorganized so that only the first *pnTrunc
** pages are in use.
*/
static int autoVacuumCommit(BtShared *pBt){
int rc = SQLITE_OK;
Pager *pPager = pBt->pPager;
VVA_ONLY( int nRef = sqlite3PagerRefcount(pPager); )
assert( sqlite3_mutex_held(pBt->mutex) );
invalidateAllOverflowCache(pBt);
assert(pBt->autoVacuum);
if( !pBt->incrVacuum ){
Pgno nFin; /* Number of pages in database after autovacuuming */
Pgno nFree; /* Number of pages on the freelist initially */
Pgno iFree; /* The next page to be freed */
Pgno nOrig; /* Database size before freeing */
nOrig = btreePagecount(pBt);
if( PTRMAP_ISPAGE(pBt, nOrig) || nOrig==PENDING_BYTE_PAGE(pBt) ){
/* It is not possible to create a database for which the final page
** is either a pointer-map page or the pending-byte page. If one
** is encountered, this indicates corruption.
*/
return SQLITE_CORRUPT_BKPT;
}
nFree = get4byte(&pBt->pPage1->aData[36]);
nFin = finalDbSize(pBt, nOrig, nFree);
if( nFin>nOrig ) return SQLITE_CORRUPT_BKPT;
if( nFin<nOrig ){
rc = saveAllCursors(pBt, 0, 0);
}
for(iFree=nOrig; iFree>nFin && rc==SQLITE_OK; iFree--){
rc = incrVacuumStep(pBt, nFin, iFree, 1);
}
if( (rc==SQLITE_DONE || rc==SQLITE_OK) && nFree>0 ){
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
put4byte(&pBt->pPage1->aData[32], 0);
put4byte(&pBt->pPage1->aData[36], 0);
put4byte(&pBt->pPage1->aData[28], nFin);
pBt->bDoTruncate = 1;
pBt->nPage = nFin;
}
if( rc!=SQLITE_OK ){
sqlite3PagerRollback(pPager);
}
}
assert( nRef>=sqlite3PagerRefcount(pPager) );
return rc;
}
#else /* ifndef SQLITE_OMIT_AUTOVACUUM */
# define setChildPtrmaps(x) SQLITE_OK
#endif
/*
** This routine does the first phase of a two-phase commit. This routine
** causes a rollback journal to be created (if it does not already exist)
** and populated with enough information so that if a power loss occurs
** the database can be restored to its original state by playing back
** the journal. Then the contents of the journal are flushed out to
** the disk. After the journal is safely on oxide, the changes to the
** database are written into the database file and flushed to oxide.
** At the end of this call, the rollback journal still exists on the
** disk and we are still holding all locks, so the transaction has not
** committed. See sqlite3BtreeCommitPhaseTwo() for the second phase of the
** commit process.
**
** This call is a no-op if no write-transaction is currently active on pBt.
**
** Otherwise, sync the database file for the btree pBt. zMaster points to
** the name of a master journal file that should be written into the
** individual journal file, or is NULL, indicating no master journal file
** (single database transaction).
**
** When this is called, the master journal should already have been
** created, populated with this journal pointer and synced to disk.
**
** Once this is routine has returned, the only thing required to commit
** the write-transaction for this database file is to delete the journal.
*/
int sqlite3BtreeCommitPhaseOne(Btree *p, const char *zMaster){
int rc = SQLITE_OK;
if( p->inTrans==TRANS_WRITE ){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
rc = autoVacuumCommit(pBt);
if( rc!=SQLITE_OK ){
sqlite3BtreeLeave(p);
return rc;
}
}
if( pBt->bDoTruncate ){
sqlite3PagerTruncateImage(pBt->pPager, pBt->nPage);
}
#endif
rc = sqlite3PagerCommitPhaseOne(pBt->pPager, zMaster, 0);
sqlite3BtreeLeave(p);
}
return rc;
}
/*
** This function is called from both BtreeCommitPhaseTwo() and BtreeRollback()
** at the conclusion of a transaction.
*/
static void btreeEndTransaction(Btree *p){
BtShared *pBt = p->pBt;
sqlite3 *db = p->db;
assert( sqlite3BtreeHoldsMutex(p) );
#ifndef SQLITE_OMIT_AUTOVACUUM
pBt->bDoTruncate = 0;
#endif
if( p->inTrans>TRANS_NONE && db->nVdbeRead>1 ){
/* If there are other active statements that belong to this database
** handle, downgrade to a read-only transaction. The other statements
** may still be reading from the database. */
downgradeAllSharedCacheTableLocks(p);
p->inTrans = TRANS_READ;
}else{
/* If the handle had any kind of transaction open, decrement the
** transaction count of the shared btree. If the transaction count
** reaches 0, set the shared state to TRANS_NONE. The unlockBtreeIfUnused()
** call below will unlock the pager. */
if( p->inTrans!=TRANS_NONE ){
clearAllSharedCacheTableLocks(p);
pBt->nTransaction--;
if( 0==pBt->nTransaction ){
pBt->inTransaction = TRANS_NONE;
}
}
/* Set the current transaction state to TRANS_NONE and unlock the
** pager if this call closed the only read or write transaction. */
p->inTrans = TRANS_NONE;
unlockBtreeIfUnused(pBt);
}
btreeIntegrity(p);
}
/*
** Commit the transaction currently in progress.
**
** This routine implements the second phase of a 2-phase commit. The
** sqlite3BtreeCommitPhaseOne() routine does the first phase and should
** be invoked prior to calling this routine. The sqlite3BtreeCommitPhaseOne()
** routine did all the work of writing information out to disk and flushing the
** contents so that they are written onto the disk platter. All this
** routine has to do is delete or truncate or zero the header in the
** the rollback journal (which causes the transaction to commit) and
** drop locks.
**
** Normally, if an error occurs while the pager layer is attempting to
** finalize the underlying journal file, this function returns an error and
** the upper layer will attempt a rollback. However, if the second argument
** is non-zero then this b-tree transaction is part of a multi-file
** transaction. In this case, the transaction has already been committed
** (by deleting a master journal file) and the caller will ignore this
** functions return code. So, even if an error occurs in the pager layer,
** reset the b-tree objects internal state to indicate that the write
** transaction has been closed. This is quite safe, as the pager will have
** transitioned to the error state.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeCommitPhaseTwo(Btree *p, int bCleanup){
if( p->inTrans==TRANS_NONE ) return SQLITE_OK;
sqlite3BtreeEnter(p);
btreeIntegrity(p);
/* If the handle has a write-transaction open, commit the shared-btrees
** transaction and set the shared state to TRANS_READ.
*/
if( p->inTrans==TRANS_WRITE ){
int rc;
BtShared *pBt = p->pBt;
assert( pBt->inTransaction==TRANS_WRITE );
assert( pBt->nTransaction>0 );
rc = sqlite3PagerCommitPhaseTwo(pBt->pPager);
if( rc!=SQLITE_OK && bCleanup==0 ){
sqlite3BtreeLeave(p);
return rc;
}
p->iDataVersion--; /* Compensate for pPager->iDataVersion++; */
pBt->inTransaction = TRANS_READ;
btreeClearHasContent(pBt);
}
btreeEndTransaction(p);
sqlite3BtreeLeave(p);
return SQLITE_OK;
}
/*
** Do both phases of a commit.
*/
int sqlite3BtreeCommit(Btree *p){
int rc;
sqlite3BtreeEnter(p);
rc = sqlite3BtreeCommitPhaseOne(p, 0);
if( rc==SQLITE_OK ){
rc = sqlite3BtreeCommitPhaseTwo(p, 0);
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** This routine sets the state to CURSOR_FAULT and the error
** code to errCode for every cursor on any BtShared that pBtree
** references. Or if the writeOnly flag is set to 1, then only
** trip write cursors and leave read cursors unchanged.
**
** Every cursor is a candidate to be tripped, including cursors
** that belong to other database connections that happen to be
** sharing the cache with pBtree.
**
** This routine gets called when a rollback occurs. If the writeOnly
** flag is true, then only write-cursors need be tripped - read-only
** cursors save their current positions so that they may continue
** following the rollback. Or, if writeOnly is false, all cursors are
** tripped. In general, writeOnly is false if the transaction being
** rolled back modified the database schema. In this case b-tree root
** pages may be moved or deleted from the database altogether, making
** it unsafe for read cursors to continue.
**
** If the writeOnly flag is true and an error is encountered while
** saving the current position of a read-only cursor, all cursors,
** including all read-cursors are tripped.
**
** SQLITE_OK is returned if successful, or if an error occurs while
** saving a cursor position, an SQLite error code.
*/
int sqlite3BtreeTripAllCursors(Btree *pBtree, int errCode, int writeOnly){
BtCursor *p;
int rc = SQLITE_OK;
assert( (writeOnly==0 || writeOnly==1) && BTCF_WriteFlag==1 );
if( pBtree ){
sqlite3BtreeEnter(pBtree);
for(p=pBtree->pBt->pCursor; p; p=p->pNext){
int i;
if( writeOnly && (p->curFlags & BTCF_WriteFlag)==0 ){
if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
rc = saveCursorPosition(p);
if( rc!=SQLITE_OK ){
(void)sqlite3BtreeTripAllCursors(pBtree, rc, 0);
break;
}
}
}else{
sqlite3BtreeClearCursor(p);
p->eState = CURSOR_FAULT;
p->skipNext = errCode;
}
for(i=0; i<=p->iPage; i++){
releasePage(p->apPage[i]);
p->apPage[i] = 0;
}
}
sqlite3BtreeLeave(pBtree);
}
return rc;
}
/*
** Rollback the transaction in progress.
**
** If tripCode is not SQLITE_OK then cursors will be invalidated (tripped).
** Only write cursors are tripped if writeOnly is true but all cursors are
** tripped if writeOnly is false. Any attempt to use
** a tripped cursor will result in an error.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeRollback(Btree *p, int tripCode, int writeOnly){
int rc;
BtShared *pBt = p->pBt;
MemPage *pPage1;
assert( writeOnly==1 || writeOnly==0 );
assert( tripCode==SQLITE_ABORT_ROLLBACK || tripCode==SQLITE_OK );
sqlite3BtreeEnter(p);
if( tripCode==SQLITE_OK ){
rc = tripCode = saveAllCursors(pBt, 0, 0);
if( rc ) writeOnly = 0;
}else{
rc = SQLITE_OK;
}
if( tripCode ){
int rc2 = sqlite3BtreeTripAllCursors(p, tripCode, writeOnly);
assert( rc==SQLITE_OK || (writeOnly==0 && rc2==SQLITE_OK) );
if( rc2!=SQLITE_OK ) rc = rc2;
}
btreeIntegrity(p);
if( p->inTrans==TRANS_WRITE ){
int rc2;
assert( TRANS_WRITE==pBt->inTransaction );
rc2 = sqlite3PagerRollback(pBt->pPager);
if( rc2!=SQLITE_OK ){
rc = rc2;
}
/* The rollback may have destroyed the pPage1->aData value. So
** call btreeGetPage() on page 1 again to make
** sure pPage1->aData is set correctly. */
if( btreeGetPage(pBt, 1, &pPage1, 0)==SQLITE_OK ){
int nPage = get4byte(28+(u8*)pPage1->aData);
testcase( nPage==0 );
if( nPage==0 ) sqlite3PagerPagecount(pBt->pPager, &nPage);
testcase( pBt->nPage!=nPage );
pBt->nPage = nPage;
releasePage(pPage1);
}
assert( countValidCursors(pBt, 1)==0 );
pBt->inTransaction = TRANS_READ;
btreeClearHasContent(pBt);
}
btreeEndTransaction(p);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Start a statement subtransaction. The subtransaction can be rolled
** back independently of the main transaction. You must start a transaction
** before starting a subtransaction. The subtransaction is ended automatically
** if the main transaction commits or rolls back.
**
** Statement subtransactions are used around individual SQL statements
** that are contained within a BEGIN...COMMIT block. If a constraint
** error occurs within the statement, the effect of that one statement
** can be rolled back without having to rollback the entire transaction.
**
** A statement sub-transaction is implemented as an anonymous savepoint. The
** value passed as the second parameter is the total number of savepoints,
** including the new anonymous savepoint, open on the B-Tree. i.e. if there
** are no active savepoints and no other statement-transactions open,
** iStatement is 1. This anonymous savepoint can be released or rolled back
** using the sqlite3BtreeSavepoint() function.
*/
int sqlite3BtreeBeginStmt(Btree *p, int iStatement){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
assert( p->inTrans==TRANS_WRITE );
assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
assert( iStatement>0 );
assert( iStatement>p->db->nSavepoint );
assert( pBt->inTransaction==TRANS_WRITE );
/* At the pager level, a statement transaction is a savepoint with
** an index greater than all savepoints created explicitly using
** SQL statements. It is illegal to open, release or rollback any
** such savepoints while the statement transaction savepoint is active.
*/
rc = sqlite3PagerOpenSavepoint(pBt->pPager, iStatement);
sqlite3BtreeLeave(p);
return rc;
}
/*
** The second argument to this function, op, is always SAVEPOINT_ROLLBACK
** or SAVEPOINT_RELEASE. This function either releases or rolls back the
** savepoint identified by parameter iSavepoint, depending on the value
** of op.
**
** Normally, iSavepoint is greater than or equal to zero. However, if op is
** SAVEPOINT_ROLLBACK, then iSavepoint may also be -1. In this case the
** contents of the entire transaction are rolled back. This is different
** from a normal transaction rollback, as no locks are released and the
** transaction remains open.
*/
int sqlite3BtreeSavepoint(Btree *p, int op, int iSavepoint){
int rc = SQLITE_OK;
if( p && p->inTrans==TRANS_WRITE ){
BtShared *pBt = p->pBt;
assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
assert( iSavepoint>=0 || (iSavepoint==-1 && op==SAVEPOINT_ROLLBACK) );
sqlite3BtreeEnter(p);
rc = sqlite3PagerSavepoint(pBt->pPager, op, iSavepoint);
if( rc==SQLITE_OK ){
if( iSavepoint<0 && (pBt->btsFlags & BTS_INITIALLY_EMPTY)!=0 ){
pBt->nPage = 0;
}
rc = newDatabase(pBt);
pBt->nPage = get4byte(28 + pBt->pPage1->aData);
/* The database size was written into the offset 28 of the header
** when the transaction started, so we know that the value at offset
** 28 is nonzero. */
assert( pBt->nPage>0 );
}
sqlite3BtreeLeave(p);
}
return rc;
}
/*
** Create a new cursor for the BTree whose root is on the page
** iTable. If a read-only cursor is requested, it is assumed that
** the caller already has at least a read-only transaction open
** on the database already. If a write-cursor is requested, then
** the caller is assumed to have an open write transaction.
**
** If the BTREE_WRCSR bit of wrFlag is clear, then the cursor can only
** be used for reading. If the BTREE_WRCSR bit is set, then the cursor
** can be used for reading or for writing if other conditions for writing
** are also met. These are the conditions that must be met in order
** for writing to be allowed:
**
** 1: The cursor must have been opened with wrFlag containing BTREE_WRCSR
**
** 2: Other database connections that share the same pager cache
** but which are not in the READ_UNCOMMITTED state may not have
** cursors open with wrFlag==0 on the same table. Otherwise
** the changes made by this write cursor would be visible to
** the read cursors in the other database connection.
**
** 3: The database must be writable (not on read-only media)
**
** 4: There must be an active transaction.
**
** The BTREE_FORDELETE bit of wrFlag may optionally be set if BTREE_WRCSR
** is set. If FORDELETE is set, that is a hint to the implementation that
** this cursor will only be used to seek to and delete entries of an index
** as part of a larger DELETE statement. The FORDELETE hint is not used by
** this implementation. But in a hypothetical alternative storage engine
** in which index entries are automatically deleted when corresponding table
** rows are deleted, the FORDELETE flag is a hint that all SEEK and DELETE
** operations on this cursor can be no-ops and all READ operations can
** return a null row (2-bytes: 0x01 0x00).
**
** No checking is done to make sure that page iTable really is the
** root page of a b-tree. If it is not, then the cursor acquired
** will not work correctly.
**
** It is assumed that the sqlite3BtreeCursorZero() has been called
** on pCur to initialize the memory space prior to invoking this routine.
*/
static int btreeCursor(
Btree *p, /* The btree */
int iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
struct KeyInfo *pKeyInfo, /* First arg to comparison function */
BtCursor *pCur /* Space for new cursor */
){
BtShared *pBt = p->pBt; /* Shared b-tree handle */
BtCursor *pX; /* Looping over other all cursors */
assert( sqlite3BtreeHoldsMutex(p) );
assert( wrFlag==0
|| wrFlag==BTREE_WRCSR
|| wrFlag==(BTREE_WRCSR|BTREE_FORDELETE)
);
/* The following assert statements verify that if this is a sharable
** b-tree database, the connection is holding the required table locks,
** and that no other connection has any open cursor that conflicts with
** this lock. */
assert( hasSharedCacheTableLock(p, iTable, pKeyInfo!=0, (wrFlag?2:1)) );
assert( wrFlag==0 || !hasReadConflicts(p, iTable) );
/* Assert that the caller has opened the required transaction. */
assert( p->inTrans>TRANS_NONE );
assert( wrFlag==0 || p->inTrans==TRANS_WRITE );
assert( pBt->pPage1 && pBt->pPage1->aData );
assert( wrFlag==0 || (pBt->btsFlags & BTS_READ_ONLY)==0 );
if( wrFlag ){
allocateTempSpace(pBt);
if( pBt->pTmpSpace==0 ) return SQLITE_NOMEM_BKPT;
}
if( iTable==1 && btreePagecount(pBt)==0 ){
assert( wrFlag==0 );
iTable = 0;
}
/* Now that no other errors can occur, finish filling in the BtCursor
** variables and link the cursor into the BtShared list. */
pCur->pgnoRoot = (Pgno)iTable;
pCur->iPage = -1;
pCur->pKeyInfo = pKeyInfo;
pCur->pBtree = p;
pCur->pBt = pBt;
pCur->curFlags = wrFlag ? BTCF_WriteFlag : 0;
pCur->curPagerFlags = wrFlag ? 0 : PAGER_GET_READONLY;
/* If there are two or more cursors on the same btree, then all such
** cursors *must* have the BTCF_Multiple flag set. */
for(pX=pBt->pCursor; pX; pX=pX->pNext){
if( pX->pgnoRoot==(Pgno)iTable ){
pX->curFlags |= BTCF_Multiple;
pCur->curFlags |= BTCF_Multiple;
}
}
pCur->pNext = pBt->pCursor;
pBt->pCursor = pCur;
pCur->eState = CURSOR_INVALID;
return SQLITE_OK;
}
int sqlite3BtreeCursor(
Btree *p, /* The btree */
int iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
struct KeyInfo *pKeyInfo, /* First arg to xCompare() */
BtCursor *pCur /* Write new cursor here */
){
int rc;
if( iTable<1 ){
rc = SQLITE_CORRUPT_BKPT;
}else{
sqlite3BtreeEnter(p);
rc = btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
sqlite3BtreeLeave(p);
}
return rc;
}
/*
** Return the size of a BtCursor object in bytes.
**
** This interfaces is needed so that users of cursors can preallocate
** sufficient storage to hold a cursor. The BtCursor object is opaque
** to users so they cannot do the sizeof() themselves - they must call
** this routine.
*/
int sqlite3BtreeCursorSize(void){
return ROUND8(sizeof(BtCursor));
}
/*
** Initialize memory that will be converted into a BtCursor object.
**
** The simple approach here would be to memset() the entire object
** to zero. But it turns out that the apPage[] and aiIdx[] arrays
** do not need to be zeroed and they are large, so we can save a lot
** of run-time by skipping the initialization of those elements.
*/
void sqlite3BtreeCursorZero(BtCursor *p){
memset(p, 0, offsetof(BtCursor, iPage));
}
/*
** Close a cursor. The read lock on the database file is released
** when the last cursor is closed.
*/
int sqlite3BtreeCloseCursor(BtCursor *pCur){
Btree *pBtree = pCur->pBtree;
if( pBtree ){
int i;
BtShared *pBt = pCur->pBt;
sqlite3BtreeEnter(pBtree);
sqlite3BtreeClearCursor(pCur);
assert( pBt->pCursor!=0 );
if( pBt->pCursor==pCur ){
pBt->pCursor = pCur->pNext;
}else{
BtCursor *pPrev = pBt->pCursor;
do{
if( pPrev->pNext==pCur ){
pPrev->pNext = pCur->pNext;
break;
}
pPrev = pPrev->pNext;
}while( ALWAYS(pPrev) );
}
for(i=0; i<=pCur->iPage; i++){
releasePage(pCur->apPage[i]);
}
unlockBtreeIfUnused(pBt);
sqlite3_free(pCur->aOverflow);
/* sqlite3_free(pCur); */
sqlite3BtreeLeave(pBtree);
}
return SQLITE_OK;
}
/*
** Make sure the BtCursor* given in the argument has a valid
** BtCursor.info structure. If it is not already valid, call
** btreeParseCell() to fill it in.
**
** BtCursor.info is a cache of the information in the current cell.
** Using this cache reduces the number of calls to btreeParseCell().
*/
#ifndef NDEBUG
static void assertCellInfo(BtCursor *pCur){
CellInfo info;
int iPage = pCur->iPage;
memset(&info, 0, sizeof(info));
btreeParseCell(pCur->apPage[iPage], pCur->aiIdx[iPage], &info);
assert( CORRUPT_DB || memcmp(&info, &pCur->info, sizeof(info))==0 );
}
#else
#define assertCellInfo(x)
#endif
static SQLITE_NOINLINE void getCellInfo(BtCursor *pCur){
if( pCur->info.nSize==0 ){
int iPage = pCur->iPage;
pCur->curFlags |= BTCF_ValidNKey;
btreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info);
}else{
assertCellInfo(pCur);
}
}
#ifndef NDEBUG /* The next routine used only within assert() statements */
/*
** Return true if the given BtCursor is valid. A valid cursor is one
** that is currently pointing to a row in a (non-empty) table.
** This is a verification routine is used only within assert() statements.
*/
int sqlite3BtreeCursorIsValid(BtCursor *pCur){
return pCur && pCur->eState==CURSOR_VALID;
}
#endif /* NDEBUG */
/*
** Return the value of the integer key or "rowid" for a table btree.
** This routine is only valid for a cursor that is pointing into a
** ordinary table btree. If the cursor points to an index btree or
** is invalid, the result of this routine is undefined.
*/
i64 sqlite3BtreeIntegerKey(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->curIntKey );
getCellInfo(pCur);
return pCur->info.nKey;
}
/*
** Return the number of bytes of payload for the entry that pCur is
** currently pointing to. For table btrees, this will be the amount
** of data. For index btrees, this will be the size of the key.
**
** The caller must guarantee that the cursor is pointing to a non-NULL
** valid entry. In other words, the calling procedure must guarantee
** that the cursor has Cursor.eState==CURSOR_VALID.
*/
u32 sqlite3BtreePayloadSize(BtCursor *pCur){
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
getCellInfo(pCur);
return pCur->info.nPayload;
}
/*
** Given the page number of an overflow page in the database (parameter
** ovfl), this function finds the page number of the next page in the
** linked list of overflow pages. If possible, it uses the auto-vacuum
** pointer-map data instead of reading the content of page ovfl to do so.
**
** If an error occurs an SQLite error code is returned. Otherwise:
**
** The page number of the next overflow page in the linked list is
** written to *pPgnoNext. If page ovfl is the last page in its linked
** list, *pPgnoNext is set to zero.
**
** If ppPage is not NULL, and a reference to the MemPage object corresponding
** to page number pOvfl was obtained, then *ppPage is set to point to that
** reference. It is the responsibility of the caller to call releasePage()
** on *ppPage to free the reference. In no reference was obtained (because
** the pointer-map was used to obtain the value for *pPgnoNext), then
** *ppPage is set to zero.
*/
static int getOverflowPage(
BtShared *pBt, /* The database file */
Pgno ovfl, /* Current overflow page number */
MemPage **ppPage, /* OUT: MemPage handle (may be NULL) */
Pgno *pPgnoNext /* OUT: Next overflow page number */
){
Pgno next = 0;
MemPage *pPage = 0;
int rc = SQLITE_OK;
assert( sqlite3_mutex_held(pBt->mutex) );
assert(pPgnoNext);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* Try to find the next page in the overflow list using the
** autovacuum pointer-map pages. Guess that the next page in
** the overflow list is page number (ovfl+1). If that guess turns
** out to be wrong, fall back to loading the data of page
** number ovfl to determine the next page number.
*/
if( pBt->autoVacuum ){
Pgno pgno;
Pgno iGuess = ovfl+1;
u8 eType;
while( PTRMAP_ISPAGE(pBt, iGuess) || iGuess==PENDING_BYTE_PAGE(pBt) ){
iGuess++;
}
if( iGuess<=btreePagecount(pBt) ){
rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
if( rc==SQLITE_OK && eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
next = iGuess;
rc = SQLITE_DONE;
}
}
}
#endif
assert( next==0 || rc==SQLITE_DONE );
if( rc==SQLITE_OK ){
rc = btreeGetPage(pBt, ovfl, &pPage, (ppPage==0) ? PAGER_GET_READONLY : 0);
assert( rc==SQLITE_OK || pPage==0 );
if( rc==SQLITE_OK ){
next = get4byte(pPage->aData);
}
}
*pPgnoNext = next;
if( ppPage ){
*ppPage = pPage;
}else{
releasePage(pPage);
}
return (rc==SQLITE_DONE ? SQLITE_OK : rc);
}
/*
** Copy data from a buffer to a page, or from a page to a buffer.
**
** pPayload is a pointer to data stored on database page pDbPage.
** If argument eOp is false, then nByte bytes of data are copied
** from pPayload to the buffer pointed at by pBuf. If eOp is true,
** then sqlite3PagerWrite() is called on pDbPage and nByte bytes
** of data are copied from the buffer pBuf to pPayload.
**
** SQLITE_OK is returned on success, otherwise an error code.
*/
static int copyPayload(
void *pPayload, /* Pointer to page data */
void *pBuf, /* Pointer to buffer */
int nByte, /* Number of bytes to copy */
int eOp, /* 0 -> copy from page, 1 -> copy to page */
DbPage *pDbPage /* Page containing pPayload */
){
if( eOp ){
/* Copy data from buffer to page (a write operation) */
int rc = sqlite3PagerWrite(pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
memcpy(pPayload, pBuf, nByte);
}else{
/* Copy data from page to buffer (a read operation) */
memcpy(pBuf, pPayload, nByte);
}
return SQLITE_OK;
}
/*
** This function is used to read or overwrite payload information
** for the entry that the pCur cursor is pointing to. The eOp
** argument is interpreted as follows:
**
** 0: The operation is a read. Populate the overflow cache.
** 1: The operation is a write. Populate the overflow cache.
** 2: The operation is a read. Do not populate the overflow cache.
**
** A total of "amt" bytes are read or written beginning at "offset".
** Data is read to or from the buffer pBuf.
**
** The content being read or written might appear on the main page
** or be scattered out on multiple overflow pages.
**
** If the current cursor entry uses one or more overflow pages and the
** eOp argument is not 2, this function may allocate space for and lazily
** populates the overflow page-list cache array (BtCursor.aOverflow).
** Subsequent calls use this cache to make seeking to the supplied offset
** more efficient.
**
** Once an overflow page-list cache has been allocated, it may be
** invalidated if some other cursor writes to the same table, or if
** the cursor is moved to a different row. Additionally, in auto-vacuum
** mode, the following events may invalidate an overflow page-list cache.
**
** * An incremental vacuum,
** * A commit in auto_vacuum="full" mode,
** * Creating a table (may require moving an overflow page).
*/
static int accessPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
u32 offset, /* Begin reading this far into payload */
u32 amt, /* Read this many bytes */
unsigned char *pBuf, /* Write the bytes into this buffer */
int eOp /* zero to read. non-zero to write. */
){
unsigned char *aPayload;
int rc = SQLITE_OK;
int iIdx = 0;
MemPage *pPage = pCur->apPage[pCur->iPage]; /* Btree page of current entry */
BtShared *pBt = pCur->pBt; /* Btree this cursor belongs to */
#ifdef SQLITE_DIRECT_OVERFLOW_READ
unsigned char * const pBufStart = pBuf;
int bEnd; /* True if reading to end of data */
#endif
assert( pPage );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
assert( cursorHoldsMutex(pCur) );
assert( eOp!=2 || offset==0 ); /* Always start from beginning for eOp==2 */
getCellInfo(pCur);
aPayload = pCur->info.pPayload;
#ifdef SQLITE_DIRECT_OVERFLOW_READ
bEnd = offset+amt==pCur->info.nPayload;
#endif
assert( offset+amt <= pCur->info.nPayload );
assert( aPayload > pPage->aData );
if( (uptr)(aPayload - pPage->aData) > (pBt->usableSize - pCur->info.nLocal) ){
/* Trying to read or write past the end of the data is an error. The
** conditional above is really:
** &aPayload[pCur->info.nLocal] > &pPage->aData[pBt->usableSize]
** but is recast into its current form to avoid integer overflow problems
*/
return SQLITE_CORRUPT_BKPT;
}
/* Check if data must be read/written to/from the btree page itself. */
if( offset<pCur->info.nLocal ){
int a = amt;
if( a+offset>pCur->info.nLocal ){
a = pCur->info.nLocal - offset;
}
rc = copyPayload(&aPayload[offset], pBuf, a, (eOp & 0x01), pPage->pDbPage);
offset = 0;
pBuf += a;
amt -= a;
}else{
offset -= pCur->info.nLocal;
}
if( rc==SQLITE_OK && amt>0 ){
const u32 ovflSize = pBt->usableSize - 4; /* Bytes content per ovfl page */
Pgno nextPage;
nextPage = get4byte(&aPayload[pCur->info.nLocal]);
/* If the BtCursor.aOverflow[] has not been allocated, allocate it now.
** Except, do not allocate aOverflow[] for eOp==2.
**
** The aOverflow[] array is sized at one entry for each overflow page
** in the overflow chain. The page number of the first overflow page is
** stored in aOverflow[0], etc. A value of 0 in the aOverflow[] array
** means "not yet known" (the cache is lazily populated).
*/
if( eOp!=2 && (pCur->curFlags & BTCF_ValidOvfl)==0 ){
int nOvfl = (pCur->info.nPayload-pCur->info.nLocal+ovflSize-1)/ovflSize;
if( nOvfl>pCur->nOvflAlloc ){
Pgno *aNew = (Pgno*)sqlite3Realloc(
pCur->aOverflow, nOvfl*2*sizeof(Pgno)
);
if( aNew==0 ){
rc = SQLITE_NOMEM_BKPT;
}else{
pCur->nOvflAlloc = nOvfl*2;
pCur->aOverflow = aNew;
}
}
if( rc==SQLITE_OK ){
memset(pCur->aOverflow, 0, nOvfl*sizeof(Pgno));
pCur->curFlags |= BTCF_ValidOvfl;
}
}
/* If the overflow page-list cache has been allocated and the
** entry for the first required overflow page is valid, skip
** directly to it.
*/
if( (pCur->curFlags & BTCF_ValidOvfl)!=0
&& pCur->aOverflow[offset/ovflSize]
){
iIdx = (offset/ovflSize);
nextPage = pCur->aOverflow[iIdx];
offset = (offset%ovflSize);
}
for( ; rc==SQLITE_OK && amt>0 && nextPage; iIdx++){
/* If required, populate the overflow page-list cache. */
if( (pCur->curFlags & BTCF_ValidOvfl)!=0 ){
assert( pCur->aOverflow[iIdx]==0
|| pCur->aOverflow[iIdx]==nextPage
|| CORRUPT_DB );
pCur->aOverflow[iIdx] = nextPage;
}
if( offset>=ovflSize ){
/* The only reason to read this page is to obtain the page
** number for the next page in the overflow chain. The page
** data is not required. So first try to lookup the overflow
** page-list cache, if any, then fall back to the getOverflowPage()
** function.
**
** Note that the aOverflow[] array must be allocated because eOp!=2
** here. If eOp==2, then offset==0 and this branch is never taken.
*/
assert( eOp!=2 );
assert( pCur->curFlags & BTCF_ValidOvfl );
assert( pCur->pBtree->db==pBt->db );
if( pCur->aOverflow[iIdx+1] ){
nextPage = pCur->aOverflow[iIdx+1];
}else{
rc = getOverflowPage(pBt, nextPage, 0, &nextPage);
}
offset -= ovflSize;
}else{
/* Need to read this page properly. It contains some of the
** range of data that is being read (eOp==0) or written (eOp!=0).
*/
#ifdef SQLITE_DIRECT_OVERFLOW_READ
sqlite3_file *fd;
#endif
int a = amt;
if( a + offset > ovflSize ){
a = ovflSize - offset;
}
#ifdef SQLITE_DIRECT_OVERFLOW_READ
/* If all the following are true:
**
** 1) this is a read operation, and
** 2) data is required from the start of this overflow page, and
** 3) the database is file-backed, and
** 4) there is no open write-transaction, and
** 5) the database is not a WAL database,
** 6) all data from the page is being read.
** 7) at least 4 bytes have already been read into the output buffer
**
** then data can be read directly from the database file into the
** output buffer, bypassing the page-cache altogether. This speeds
** up loading large records that span many overflow pages.
*/
if( (eOp&0x01)==0 /* (1) */
&& offset==0 /* (2) */
&& (bEnd || a==ovflSize) /* (6) */
&& pBt->inTransaction==TRANS_READ /* (4) */
&& (fd = sqlite3PagerFile(pBt->pPager))->pMethods /* (3) */
&& pBt->pPage1->aData[19]==0x01 /* (5) */
&& &pBuf[-4]>=pBufStart /* (7) */
){
u8 aSave[4];
u8 *aWrite = &pBuf[-4];
assert( aWrite>=pBufStart ); /* hence (7) */
memcpy(aSave, aWrite, 4);
rc = sqlite3OsRead(fd, aWrite, a+4, (i64)pBt->pageSize*(nextPage-1));
nextPage = get4byte(aWrite);
memcpy(aWrite, aSave, 4);
}else
#endif
{
DbPage *pDbPage;
rc = sqlite3PagerGet(pBt->pPager, nextPage, &pDbPage,
((eOp&0x01)==0 ? PAGER_GET_READONLY : 0)
);
if( rc==SQLITE_OK ){
aPayload = sqlite3PagerGetData(pDbPage);
nextPage = get4byte(aPayload);
rc = copyPayload(&aPayload[offset+4], pBuf, a, (eOp&0x01), pDbPage);
sqlite3PagerUnref(pDbPage);
offset = 0;
}
}
amt -= a;
pBuf += a;
}
}
}
if( rc==SQLITE_OK && amt>0 ){
return SQLITE_CORRUPT_BKPT;
}
return rc;
}
/*
** Read part of the key associated with cursor pCur. Exactly
** "amt" bytes will be transferred into pBuf[]. The transfer
** begins at "offset".
**
** The caller must ensure that pCur is pointing to a valid row
** in the table.
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong. An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeKey(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
assert( cursorHoldsMutex(pCur) );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
return accessPayload(pCur, offset, amt, (unsigned char*)pBuf, 0);
}
/*
** Read part of the data associated with cursor pCur. Exactly
** "amt" bytes will be transfered into pBuf[]. The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong. An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
int rc;
#ifndef SQLITE_OMIT_INCRBLOB
if ( pCur->eState==CURSOR_INVALID ){
return SQLITE_ABORT;
}
#endif
assert( cursorOwnsBtShared(pCur) );
rc = restoreCursorPosition(pCur);
if( rc==SQLITE_OK ){
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
rc = accessPayload(pCur, offset, amt, pBuf, 0);
}
return rc;
}
/*
** Return a pointer to payload information from the entry that the
** pCur cursor is pointing to. The pointer is to the beginning of
** the key if index btrees (pPage->intKey==0) and is the data for
** table btrees (pPage->intKey==1). The number of bytes of available
** key/data is written into *pAmt. If *pAmt==0, then the value
** returned will not be a valid pointer.
**
** This routine is an optimization. It is common for the entire key
** and data to fit on the local page and for there to be no overflow
** pages. When that is so, this routine can be used to access the
** key and data without making a copy. If the key and/or data spills
** onto overflow pages, then accessPayload() must be used to reassemble
** the key/data and copy it into a preallocated buffer.
**
** The pointer returned by this routine looks directly into the cached
** page of the database. The data might change or move the next time
** any btree routine is called.
*/
static const void *fetchPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
u32 *pAmt /* Write the number of available bytes here */
){
u32 amt;
assert( pCur!=0 && pCur->iPage>=0 && pCur->apPage[pCur->iPage]);
assert( pCur->eState==CURSOR_VALID );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
assert( cursorOwnsBtShared(pCur) );
assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
assert( pCur->info.nSize>0 );
assert( pCur->info.pPayload>pCur->apPage[pCur->iPage]->aData || CORRUPT_DB );
assert( pCur->info.pPayload<pCur->apPage[pCur->iPage]->aDataEnd ||CORRUPT_DB);
amt = (int)(pCur->apPage[pCur->iPage]->aDataEnd - pCur->info.pPayload);
if( pCur->info.nLocal<amt ) amt = pCur->info.nLocal;
*pAmt = amt;
return (void*)pCur->info.pPayload;
}
/*
** For the entry that cursor pCur is point to, return as
** many bytes of the key or data as are available on the local
** b-tree page. Write the number of available bytes into *pAmt.
**
** The pointer returned is ephemeral. The key/data may move
** or be destroyed on the next call to any Btree routine,
** including calls from other threads against the same cache.
** Hence, a mutex on the BtShared should be held prior to calling
** this routine.
**
** These routines is used to get quick access to key and data
** in the common case where no overflow pages are used.
*/
const void *sqlite3BtreePayloadFetch(BtCursor *pCur, u32 *pAmt){
return fetchPayload(pCur, pAmt);
}
/*
** Move the cursor down to a new child page. The newPgno argument is the
** page number of the child page to move to.
**
** This function returns SQLITE_CORRUPT if the page-header flags field of
** the new child page does not match the flags field of the parent (i.e.
** if an intkey page appears to be the parent of a non-intkey page, or
** vice-versa).
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
BtShared *pBt = pCur->pBt;
assert( cursorOwnsBtShared(pCur) );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage<BTCURSOR_MAX_DEPTH );
assert( pCur->iPage>=0 );
if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
return SQLITE_CORRUPT_BKPT;
}
pCur->info.nSize = 0;
pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
pCur->iPage++;
pCur->aiIdx[pCur->iPage] = 0;
return getAndInitPage(pBt, newPgno, &pCur->apPage[pCur->iPage],
pCur, pCur->curPagerFlags);
}
#if SQLITE_DEBUG
/*
** Page pParent is an internal (non-leaf) tree page. This function
** asserts that page number iChild is the left-child if the iIdx'th
** cell in page pParent. Or, if iIdx is equal to the total number of
** cells in pParent, that page number iChild is the right-child of
** the page.
*/
static void assertParentIndex(MemPage *pParent, int iIdx, Pgno iChild){
if( CORRUPT_DB ) return; /* The conditions tested below might not be true
** in a corrupt database */
assert( iIdx<=pParent->nCell );
if( iIdx==pParent->nCell ){
assert( get4byte(&pParent->aData[pParent->hdrOffset+8])==iChild );
}else{
assert( get4byte(findCell(pParent, iIdx))==iChild );
}
}
#else
# define assertParentIndex(x,y,z)
#endif
/*
** Move the cursor up to the parent page.
**
** pCur->idx is set to the cell index that contains the pointer
** to the page we are coming from. If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
static void moveToParent(BtCursor *pCur){
assert( cursorOwnsBtShared(pCur) );
assert( pCur->eState==CURSOR_VALID );
assert( pCur->iPage>0 );
assert( pCur->apPage[pCur->iPage] );
assertParentIndex(
pCur->apPage[pCur->iPage-1],
pCur->aiIdx[pCur->iPage-1],
pCur->apPage[pCur->iPage]->pgno
);
testcase( pCur->aiIdx[pCur->iPage-1] > pCur->apPage[pCur->iPage-1]->nCell );
pCur->info.nSize = 0;
pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
releasePageNotNull(pCur->apPage[pCur->iPage--]);
}
/*
** Move the cursor to point to the root page of its b-tree structure.
**
** If the table has a virtual root page, then the cursor is moved to point
** to the virtual root page instead of the actual root page. A table has a
** virtual root page when the actual root page contains no cells and a
** single child page. This can only happen with the table rooted at page 1.
**
** If the b-tree structure is empty, the cursor state is set to
** CURSOR_INVALID. Otherwise, the cursor is set to point to the first
** cell located on the root (or virtual root) page and the cursor state
** is set to CURSOR_VALID.
**
** If this function returns successfully, it may be assumed that the
** page-header flags indicate that the [virtual] root-page is the expected
** kind of b-tree page (i.e. if when opening the cursor the caller did not
** specify a KeyInfo structure the flags byte is set to 0x05 or 0x0D,
** indicating a table b-tree, or if the caller did specify a KeyInfo
** structure the flags byte is set to 0x02 or 0x0A, indicating an index
** b-tree).
*/
static int moveToRoot(BtCursor *pCur){
MemPage *pRoot;
int rc = SQLITE_OK;
assert( cursorOwnsBtShared(pCur) );
assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
assert( CURSOR_VALID < CURSOR_REQUIRESEEK );
assert( CURSOR_FAULT > CURSOR_REQUIRESEEK );
if( pCur->eState>=CURSOR_REQUIRESEEK ){
if( pCur->eState==CURSOR_FAULT ){
assert( pCur->skipNext!=SQLITE_OK );
return pCur->skipNext;
}
sqlite3BtreeClearCursor(pCur);
}
if( pCur->iPage>=0 ){
while( pCur->iPage ){
assert( pCur->apPage[pCur->iPage]!=0 );
releasePageNotNull(pCur->apPage[pCur->iPage--]);
}
}else if( pCur->pgnoRoot==0 ){
pCur->eState = CURSOR_INVALID;
return SQLITE_OK;
}else{
assert( pCur->iPage==(-1) );
rc = getAndInitPage(pCur->pBtree->pBt, pCur->pgnoRoot, &pCur->apPage[0],
0, pCur->curPagerFlags);
if( rc!=SQLITE_OK ){
pCur->eState = CURSOR_INVALID;
return rc;
}
pCur->iPage = 0;
pCur->curIntKey = pCur->apPage[0]->intKey;
}
pRoot = pCur->apPage[0];
assert( pRoot->pgno==pCur->pgnoRoot );
/* If pCur->pKeyInfo is not NULL, then the caller that opened this cursor
** expected to open it on an index b-tree. Otherwise, if pKeyInfo is
** NULL, the caller expects a table b-tree. If this is not the case,
** return an SQLITE_CORRUPT error.
**
** Earlier versions of SQLite assumed that this test could not fail
** if the root page was already loaded when this function was called (i.e.
** if pCur->iPage>=0). But this is not so if the database is corrupted
** in such a way that page pRoot is linked into a second b-tree table
** (or the freelist). */
assert( pRoot->intKey==1 || pRoot->intKey==0 );
if( pRoot->isInit==0 || (pCur->pKeyInfo==0)!=pRoot->intKey ){
return SQLITE_CORRUPT_BKPT;
}
pCur->aiIdx[0] = 0;
pCur->info.nSize = 0;
pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidNKey|BTCF_ValidOvfl);
if( pRoot->nCell>0 ){
pCur->eState = CURSOR_VALID;
}else if( !pRoot->leaf ){
Pgno subpage;
if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT;
subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
pCur->eState = CURSOR_VALID;
rc = moveToChild(pCur, subpage);
}else{
pCur->eState = CURSOR_INVALID;
}
return rc;
}
/*
** Move the cursor down to the left-most leaf entry beneath the
** entry to which it is currently pointing.
**
** The left-most leaf is the one with the smallest key - the first
** in ascending order.
*/
static int moveToLeftmost(BtCursor *pCur){
Pgno pgno;
int rc = SQLITE_OK;
MemPage *pPage;
assert( cursorOwnsBtShared(pCur) );
assert( pCur->eState==CURSOR_VALID );
while( rc==SQLITE_OK && !(pPage = pCur->apPage[pCur->iPage])->leaf ){
assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
pgno = get4byte(findCell(pPage, pCur->aiIdx[pCur->iPage]));
rc = moveToChild(pCur, pgno);
}
return rc;
}
/*
** Move the cursor down to the right-most leaf entry beneath the
** page to which it is currently pointing. Notice the difference
** between moveToLeftmost() and moveToRightmost(). moveToLeftmost()
** finds the left-most entry beneath the *entry* whereas moveToRightmost()
** finds the right-most entry beneath the *page*.
**
** The right-most entry is the one with the largest key - the last
** key in ascending order.
*/
static int moveToRightmost(BtCursor *pCur){
Pgno pgno;
int rc = SQLITE_OK;
MemPage *pPage = 0;
assert( cursorOwnsBtShared(pCur) );
assert( pCur->eState==CURSOR_VALID );
while( !(pPage = pCur->apPage[pCur->iPage])->leaf ){
pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
pCur->aiIdx[pCur->iPage] = pPage->nCell;
rc = moveToChild(pCur, pgno);
if( rc ) return rc;
}
pCur->aiIdx[pCur->iPage] = pPage->nCell-1;
assert( pCur->info.nSize==0 );
assert( (pCur->curFlags & BTCF_ValidNKey)==0 );
return SQLITE_OK;
}
/* Move the cursor to the first entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
int rc;
assert( cursorOwnsBtShared(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
rc = moveToRoot(pCur);
if( rc==SQLITE_OK ){
if( pCur->eState==CURSOR_INVALID ){
assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
*pRes = 1;
}else{
assert( pCur->apPage[pCur->iPage]->nCell>0 );
*pRes = 0;
rc = moveToLeftmost(pCur);
}
}
return rc;
}
/* Move the cursor to the last entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
int rc;
assert( cursorOwnsBtShared(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
/* If the cursor already points to the last entry, this is a no-op. */
if( CURSOR_VALID==pCur->eState && (pCur->curFlags & BTCF_AtLast)!=0 ){
#ifdef SQLITE_DEBUG
/* This block serves to assert() that the cursor really does point
** to the last entry in the b-tree. */
int ii;
for(ii=0; ii<pCur->iPage; ii++){
assert( pCur->aiIdx[ii]==pCur->apPage[ii]->nCell );
}
assert( pCur->aiIdx[pCur->iPage]==pCur->apPage[pCur->iPage]->nCell-1 );
assert( pCur->apPage[pCur->iPage]->leaf );
#endif
return SQLITE_OK;
}
rc = moveToRoot(pCur);
if( rc==SQLITE_OK ){
if( CURSOR_INVALID==pCur->eState ){
assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
*pRes = 1;
}else{
assert( pCur->eState==CURSOR_VALID );
*pRes = 0;
rc = moveToRightmost(pCur);
if( rc==SQLITE_OK ){
pCur->curFlags |= BTCF_AtLast;
}else{
pCur->curFlags &= ~BTCF_AtLast;
}
}
}
return rc;
}
/* Move the cursor so that it points to an entry near the key
** specified by pIdxKey or intKey. Return a success code.
**
** For INTKEY tables, the intKey parameter is used. pIdxKey
** must be NULL. For index tables, pIdxKey is used and intKey
** is ignored.
**
** If an exact match is not found, then the cursor is always
** left pointing at a leaf page which would hold the entry if it
** were present. The cursor might point to an entry that comes
** before or after the key.
**
** An integer is written into *pRes which is the result of
** comparing the key with the entry to which the cursor is
** pointing. The meaning of the integer written into
** *pRes is as follows:
**
** *pRes<0 The cursor is left pointing at an entry that
** is smaller than intKey/pIdxKey or if the table is empty
** and the cursor is therefore left point to nothing.
**
** *pRes==0 The cursor is left pointing at an entry that
** exactly matches intKey/pIdxKey.
**
** *pRes>0 The cursor is left pointing at an entry that
** is larger than intKey/pIdxKey.
**
** For index tables, the pIdxKey->eqSeen field is set to 1 if there
** exists an entry in the table that exactly matches pIdxKey.
*/
int sqlite3BtreeMovetoUnpacked(
BtCursor *pCur, /* The cursor to be moved */
UnpackedRecord *pIdxKey, /* Unpacked index key */
i64 intKey, /* The table key */
int biasRight, /* If true, bias the search to the high end */
int *pRes /* Write search results here */
){
int rc;
RecordCompare xRecordCompare;
assert( cursorOwnsBtShared(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
assert( pRes );
assert( (pIdxKey==0)==(pCur->pKeyInfo==0) );
assert( pCur->eState!=CURSOR_VALID || (pIdxKey==0)==(pCur->curIntKey!=0) );
/* If the cursor is already positioned at the point we are trying
** to move to, then just return without doing any work */
if( pIdxKey==0
&& pCur->eState==CURSOR_VALID && (pCur->curFlags & BTCF_ValidNKey)!=0
){
if( pCur->info.nKey==intKey ){
*pRes = 0;
return SQLITE_OK;
}
if( (pCur->curFlags & BTCF_AtLast)!=0 && pCur->info.nKey<intKey ){
*pRes = -1;
return SQLITE_OK;
}
}
if( pIdxKey ){
xRecordCompare = sqlite3VdbeFindCompare(pIdxKey);
pIdxKey->errCode = 0;
assert( pIdxKey->default_rc==1
|| pIdxKey->default_rc==0
|| pIdxKey->default_rc==-1
);
}else{
xRecordCompare = 0; /* All keys are integers */
}
rc = moveToRoot(pCur);
if( rc ){
return rc;
}
assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage] );
assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->isInit );
assert( pCur->eState==CURSOR_INVALID || pCur->apPage[pCur->iPage]->nCell>0 );
if( pCur->eState==CURSOR_INVALID ){
*pRes = -1;
assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
return SQLITE_OK;
}
assert( pCur->apPage[0]->intKey==pCur->curIntKey );
assert( pCur->curIntKey || pIdxKey );
for(;;){
int lwr, upr, idx, c;
Pgno chldPg;
MemPage *pPage = pCur->apPage[pCur->iPage];
u8 *pCell; /* Pointer to current cell in pPage */
/* pPage->nCell must be greater than zero. If this is the root-page
** the cursor would have been INVALID above and this for(;;) loop
** not run. If this is not the root-page, then the moveToChild() routine
** would have already detected db corruption. Similarly, pPage must
** be the right kind (index or table) of b-tree page. Otherwise
** a moveToChild() or moveToRoot() call would have detected corruption. */
assert( pPage->nCell>0 );
assert( pPage->intKey==(pIdxKey==0) );
lwr = 0;
upr = pPage->nCell-1;
assert( biasRight==0 || biasRight==1 );
idx = upr>>(1-biasRight); /* idx = biasRight ? upr : (lwr+upr)/2; */
pCur->aiIdx[pCur->iPage] = (u16)idx;
if( xRecordCompare==0 ){
for(;;){
i64 nCellKey;
pCell = findCellPastPtr(pPage, idx);
if( pPage->intKeyLeaf ){
while( 0x80 <= *(pCell++) ){
if( pCell>=pPage->aDataEnd ) return SQLITE_CORRUPT_BKPT;
}
}
getVarint(pCell, (u64*)&nCellKey);
if( nCellKey<intKey ){
lwr = idx+1;
if( lwr>upr ){ c = -1; break; }
}else if( nCellKey>intKey ){
upr = idx-1;
if( lwr>upr ){ c = +1; break; }
}else{
assert( nCellKey==intKey );
pCur->curFlags |= BTCF_ValidNKey;
pCur->info.nKey = nCellKey;
pCur->aiIdx[pCur->iPage] = (u16)idx;
if( !pPage->leaf ){
lwr = idx;
goto moveto_next_layer;
}else{
*pRes = 0;
rc = SQLITE_OK;
goto moveto_finish;
}
}
assert( lwr+upr>=0 );
idx = (lwr+upr)>>1; /* idx = (lwr+upr)/2; */
}
}else{
for(;;){
int nCell; /* Size of the pCell cell in bytes */
pCell = findCellPastPtr(pPage, idx);
/* The maximum supported page-size is 65536 bytes. This means that
** the maximum number of record bytes stored on an index B-Tree
** page is less than 16384 bytes and may be stored as a 2-byte
** varint. This information is used to attempt to avoid parsing
** the entire cell by checking for the cases where the record is
** stored entirely within the b-tree page by inspecting the first
** 2 bytes of the cell.
*/
nCell = pCell[0];
if( nCell<=pPage->max1bytePayload ){
/* This branch runs if the record-size field of the cell is a
** single byte varint and the record fits entirely on the main
** b-tree page. */
testcase( pCell+nCell+1==pPage->aDataEnd );
c = xRecordCompare(nCell, (void*)&pCell[1], pIdxKey);
}else if( !(pCell[1] & 0x80)
&& (nCell = ((nCell&0x7f)<<7) + pCell[1])<=pPage->maxLocal
){
/* The record-size field is a 2 byte varint and the record
** fits entirely on the main b-tree page. */
testcase( pCell+nCell+2==pPage->aDataEnd );
c = xRecordCompare(nCell, (void*)&pCell[2], pIdxKey);
}else{
/* The record flows over onto one or more overflow pages. In
** this case the whole cell needs to be parsed, a buffer allocated
** and accessPayload() used to retrieve the record into the
** buffer before VdbeRecordCompare() can be called.
**
** If the record is corrupt, the xRecordCompare routine may read
** up to two varints past the end of the buffer. An extra 18
** bytes of padding is allocated at the end of the buffer in
** case this happens. */
void *pCellKey;
u8 * const pCellBody = pCell - pPage->childPtrSize;
pPage->xParseCell(pPage, pCellBody, &pCur->info);
nCell = (int)pCur->info.nKey;
testcase( nCell<0 ); /* True if key size is 2^32 or more */
testcase( nCell==0 ); /* Invalid key size: 0x80 0x80 0x00 */
testcase( nCell==1 ); /* Invalid key size: 0x80 0x80 0x01 */
testcase( nCell==2 ); /* Minimum legal index key size */
if( nCell<2 ){
rc = SQLITE_CORRUPT_BKPT;
goto moveto_finish;
}
pCellKey = sqlite3Malloc( nCell+18 );
if( pCellKey==0 ){
rc = SQLITE_NOMEM_BKPT;
goto moveto_finish;
}
pCur->aiIdx[pCur->iPage] = (u16)idx;
rc = accessPayload(pCur, 0, nCell, (unsigned char*)pCellKey, 2);
if( rc ){
sqlite3_free(pCellKey);
goto moveto_finish;
}
c = xRecordCompare(nCell, pCellKey, pIdxKey);
sqlite3_free(pCellKey);
}
assert(
(pIdxKey->errCode!=SQLITE_CORRUPT || c==0)
&& (pIdxKey->errCode!=SQLITE_NOMEM || pCur->pBtree->db->mallocFailed)
);
if( c<0 ){
lwr = idx+1;
}else if( c>0 ){
upr = idx-1;
}else{
assert( c==0 );
*pRes = 0;
rc = SQLITE_OK;
pCur->aiIdx[pCur->iPage] = (u16)idx;
if( pIdxKey->errCode ) rc = SQLITE_CORRUPT;
goto moveto_finish;
}
if( lwr>upr ) break;
assert( lwr+upr>=0 );
idx = (lwr+upr)>>1; /* idx = (lwr+upr)/2 */
}
}
assert( lwr==upr+1 || (pPage->intKey && !pPage->leaf) );
assert( pPage->isInit );
if( pPage->leaf ){
assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
pCur->aiIdx[pCur->iPage] = (u16)idx;
*pRes = c;
rc = SQLITE_OK;
goto moveto_finish;
}
moveto_next_layer:
if( lwr>=pPage->nCell ){
chldPg = get4byte(&pPage->aData[pPage->hdrOffset+8]);
}else{
chldPg = get4byte(findCell(pPage, lwr));
}
pCur->aiIdx[pCur->iPage] = (u16)lwr;
rc = moveToChild(pCur, chldPg);
if( rc ) break;
}
moveto_finish:
pCur->info.nSize = 0;
pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
return rc;
}
/*
** Return TRUE if the cursor is not pointing at an entry of the table.
**
** TRUE will be returned after a call to sqlite3BtreeNext() moves
** past the last entry in the table or sqlite3BtreePrev() moves past
** the first entry. TRUE is also returned if the table is empty.
*/
int sqlite3BtreeEof(BtCursor *pCur){
/* TODO: What if the cursor is in CURSOR_REQUIRESEEK but all table entries
** have been deleted? This API will need to change to return an error code
** as well as the boolean result value.
*/
return (CURSOR_VALID!=pCur->eState);
}
/*
** Advance the cursor to the next entry in the database. If
** successful then set *pRes=0. If the cursor
** was already pointing to the last entry in the database before
** this routine was called, then set *pRes=1.
**
** The main entry point is sqlite3BtreeNext(). That routine is optimized
** for the common case of merely incrementing the cell counter BtCursor.aiIdx
** to the next cell on the current page. The (slower) btreeNext() helper
** routine is called when it is necessary to move to a different page or
** to restore the cursor.
**
** The calling function will set *pRes to 0 or 1. The initial *pRes value
** will be 1 if the cursor being stepped corresponds to an SQL index and
** if this routine could have been skipped if that SQL index had been
** a unique index. Otherwise the caller will have set *pRes to zero.
** Zero is the common case. The btree implementation is free to use the
** initial *pRes value as a hint to improve performance, but the current
** SQLite btree implementation does not. (Note that the comdb2 btree
** implementation does use this hint, however.)
*/
static SQLITE_NOINLINE int btreeNext(BtCursor *pCur, int *pRes){
int rc;
int idx;
MemPage *pPage;
assert( cursorOwnsBtShared(pCur) );
assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
assert( *pRes==0 );
if( pCur->eState!=CURSOR_VALID ){
assert( (pCur->curFlags & BTCF_ValidOvfl)==0 );
rc = restoreCursorPosition(pCur);
if( rc!=SQLITE_OK ){
return rc;
}
if( CURSOR_INVALID==pCur->eState ){
*pRes = 1;
return SQLITE_OK;
}
if( pCur->skipNext ){
assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_SKIPNEXT );
pCur->eState = CURSOR_VALID;
if( pCur->skipNext>0 ){
pCur->skipNext = 0;
return SQLITE_OK;
}
pCur->skipNext = 0;
}
}
pPage = pCur->apPage[pCur->iPage];
idx = ++pCur->aiIdx[pCur->iPage];
assert( pPage->isInit );
/* If the database file is corrupt, it is possible for the value of idx
** to be invalid here. This can only occur if a second cursor modifies
** the page while cursor pCur is holding a reference to it. Which can
** only happen if the database is corrupt in such a way as to link the
** page into more than one b-tree structure. */
testcase( idx>pPage->nCell );
if( idx>=pPage->nCell ){
if( !pPage->leaf ){
rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
if( rc ) return rc;
return moveToLeftmost(pCur);
}
do{
if( pCur->iPage==0 ){
*pRes = 1;
pCur->eState = CURSOR_INVALID;
return SQLITE_OK;
}
moveToParent(pCur);
pPage = pCur->apPage[pCur->iPage];
}while( pCur->aiIdx[pCur->iPage]>=pPage->nCell );
if( pPage->intKey ){
return sqlite3BtreeNext(pCur, pRes);
}else{
return SQLITE_OK;
}
}
if( pPage->leaf ){
return SQLITE_OK;
}else{
return moveToLeftmost(pCur);
}
}
int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
MemPage *pPage;
assert( cursorOwnsBtShared(pCur) );
assert( pRes!=0 );
assert( *pRes==0 || *pRes==1 );
assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
pCur->info.nSize = 0;
pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
*pRes = 0;
if( pCur->eState!=CURSOR_VALID ) return btreeNext(pCur, pRes);
pPage = pCur->apPage[pCur->iPage];
if( (++pCur->aiIdx[pCur->iPage])>=pPage->nCell ){
pCur->aiIdx[pCur->iPage]--;
return btreeNext(pCur, pRes);
}
if( pPage->leaf ){
return SQLITE_OK;
}else{
return moveToLeftmost(pCur);
}
}
/*
** Step the cursor to the back to the previous entry in the database. If
** successful then set *pRes=0. If the cursor
** was already pointing to the first entry in the database before
** this routine was called, then set *pRes=1.
**
** The main entry point is sqlite3BtreePrevious(). That routine is optimized
** for the common case of merely decrementing the cell counter BtCursor.aiIdx
** to the previous cell on the current page. The (slower) btreePrevious()
** helper routine is called when it is necessary to move to a different page
** or to restore the cursor.
**
** The calling function will set *pRes to 0 or 1. The initial *pRes value
** will be 1 if the cursor being stepped corresponds to an SQL index and
** if this routine could have been skipped if that SQL index had been
** a unique index. Otherwise the caller will have set *pRes to zero.
** Zero is the common case. The btree implementation is free to use the
** initial *pRes value as a hint to improve performance, but the current
** SQLite btree implementation does not. (Note that the comdb2 btree
** implementation does use this hint, however.)
*/
static SQLITE_NOINLINE int btreePrevious(BtCursor *pCur, int *pRes){
int rc;
MemPage *pPage;
assert( cursorOwnsBtShared(pCur) );
assert( pRes!=0 );
assert( *pRes==0 );
assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
assert( (pCur->curFlags & (BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey))==0 );
assert( pCur->info.nSize==0 );
if( pCur->eState!=CURSOR_VALID ){
rc = restoreCursorPosition(pCur);
if( rc!=SQLITE_OK ){
return rc;
}
if( CURSOR_INVALID==pCur->eState ){
*pRes = 1;
return SQLITE_OK;
}
if( pCur->skipNext ){
assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_SKIPNEXT );
pCur->eState = CURSOR_VALID;
if( pCur->skipNext<0 ){
pCur->skipNext = 0;
return SQLITE_OK;
}
pCur->skipNext = 0;
}
}
pPage = pCur->apPage[pCur->iPage];
assert( pPage->isInit );
if( !pPage->leaf ){
int idx = pCur->aiIdx[pCur->iPage];
rc = moveToChild(pCur, get4byte(findCell(pPage, idx)));
if( rc ) return rc;
rc = moveToRightmost(pCur);
}else{
while( pCur->aiIdx[pCur->iPage]==0 ){
if( pCur->iPage==0 ){
pCur->eState = CURSOR_INVALID;
*pRes = 1;
return SQLITE_OK;
}
moveToParent(pCur);
}
assert( pCur->info.nSize==0 );
assert( (pCur->curFlags & (BTCF_ValidNKey|BTCF_ValidOvfl))==0 );
pCur->aiIdx[pCur->iPage]--;
pPage = pCur->apPage[pCur->iPage];
if( pPage->intKey && !pPage->leaf ){
rc = sqlite3BtreePrevious(pCur, pRes);
}else{
rc = SQLITE_OK;
}
}
return rc;
}
int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
assert( cursorOwnsBtShared(pCur) );
assert( pRes!=0 );
assert( *pRes==0 || *pRes==1 );
assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
*pRes = 0;
pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey);
pCur->info.nSize = 0;
if( pCur->eState!=CURSOR_VALID
|| pCur->aiIdx[pCur->iPage]==0
|| pCur->apPage[pCur->iPage]->leaf==0
){
return btreePrevious(pCur, pRes);
}
pCur->aiIdx[pCur->iPage]--;
return SQLITE_OK;
}
/*
** Allocate a new page from the database file.
**
** The new page is marked as dirty. (In other words, sqlite3PagerWrite()
** has already been called on the new page.) The new page has also
** been referenced and the calling routine is responsible for calling
** sqlite3PagerUnref() on the new page when it is done.
**
** SQLITE_OK is returned on success. Any other return value indicates
** an error. *ppPage is set to NULL in the event of an error.
**
** If the "nearby" parameter is not 0, then an effort is made to
** locate a page close to the page number "nearby". This can be used in an
** attempt to keep related pages close to each other in the database file,
** which in turn can make database access faster.
**
** If the eMode parameter is BTALLOC_EXACT and the nearby page exists
** anywhere on the free-list, then it is guaranteed to be returned. If
** eMode is BTALLOC_LT then the page returned will be less than or equal
** to nearby if any such page exists. If eMode is BTALLOC_ANY then there
** are no restrictions on which page is returned.
*/
static int allocateBtreePage(
BtShared *pBt, /* The btree */
MemPage **ppPage, /* Store pointer to the allocated page here */
Pgno *pPgno, /* Store the page number here */
Pgno nearby, /* Search for a page near this one */
u8 eMode /* BTALLOC_EXACT, BTALLOC_LT, or BTALLOC_ANY */
){
MemPage *pPage1;
int rc;
u32 n; /* Number of pages on the freelist */
u32 k; /* Number of leaves on the trunk of the freelist */
MemPage *pTrunk = 0;
MemPage *pPrevTrunk = 0;
Pgno mxPage; /* Total size of the database file */
assert( sqlite3_mutex_held(pBt->mutex) );
assert( eMode==BTALLOC_ANY || (nearby>0 && IfNotOmitAV(pBt->autoVacuum)) );
pPage1 = pBt->pPage1;
mxPage = btreePagecount(pBt);
/* EVIDENCE-OF: R-05119-02637 The 4-byte big-endian integer at offset 36
** stores stores the total number of pages on the freelist. */
n = get4byte(&pPage1->aData[36]);
testcase( n==mxPage-1 );
if( n>=mxPage ){
return SQLITE_CORRUPT_BKPT;
}
if( n>0 ){
/* There are pages on the freelist. Reuse one of those pages. */
Pgno iTrunk;
u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
u32 nSearch = 0; /* Count of the number of search attempts */
/* If eMode==BTALLOC_EXACT and a query of the pointer-map
** shows that the page 'nearby' is somewhere on the free-list, then
** the entire-list will be searched for that page.
*/
#ifndef SQLITE_OMIT_AUTOVACUUM
if( eMode==BTALLOC_EXACT ){
if( nearby<=mxPage ){
u8 eType;
assert( nearby>0 );
assert( pBt->autoVacuum );
rc = ptrmapGet(pBt, nearby, &eType, 0);
if( rc ) return rc;
if( eType==PTRMAP_FREEPAGE ){
searchList = 1;
}
}
}else if( eMode==BTALLOC_LE ){
searchList = 1;
}
#endif
/* Decrement the free-list count by 1. Set iTrunk to the index of the
** first free-list trunk page. iPrevTrunk is initially 1.
*/
rc = sqlite3PagerWrite(pPage1->pDbPage);
if( rc ) return rc;
put4byte(&pPage1->aData[36], n-1);
/* The code within this loop is run only once if the 'searchList' variable
** is not true. Otherwise, it runs once for each trunk-page on the
** free-list until the page 'nearby' is located (eMode==BTALLOC_EXACT)
** or until a page less than 'nearby' is located (eMode==BTALLOC_LT)
*/
do {
pPrevTrunk = pTrunk;
if( pPrevTrunk ){
/* EVIDENCE-OF: R-01506-11053 The first integer on a freelist trunk page
** is the page number of the next freelist trunk page in the list or
** zero if this is the last freelist trunk page. */
iTrunk = get4byte(&pPrevTrunk->aData[0]);
}else{
/* EVIDENCE-OF: R-59841-13798 The 4-byte big-endian integer at offset 32
** stores the page number of the first page of the freelist, or zero if
** the freelist is empty. */
iTrunk = get4byte(&pPage1->aData[32]);
}
testcase( iTrunk==mxPage );
if( iTrunk>mxPage || nSearch++ > n ){
rc = SQLITE_CORRUPT_BKPT;
}else{
rc = btreeGetUnusedPage(pBt, iTrunk, &pTrunk, 0);
}
if( rc ){
pTrunk = 0;
goto end_allocate_page;
}
assert( pTrunk!=0 );
assert( pTrunk->aData!=0 );
/* EVIDENCE-OF: R-13523-04394 The second integer on a freelist trunk page
** is the number of leaf page pointers to follow. */
k = get4byte(&pTrunk->aData[4]);
if( k==0 && !searchList ){
/* The trunk has no leaves and the list is not being searched.
** So extract the trunk page itself and use it as the newly
** allocated page */
assert( pPrevTrunk==0 );
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
*pPgno = iTrunk;
memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
*ppPage = pTrunk;
pTrunk = 0;
TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
}else if( k>(u32)(pBt->usableSize/4 - 2) ){
/* Value of k is out of range. Database corruption */
rc = SQLITE_CORRUPT_BKPT;
goto end_allocate_page;
#ifndef SQLITE_OMIT_AUTOVACUUM
}else if( searchList
&& (nearby==iTrunk || (iTrunk<nearby && eMode==BTALLOC_LE))
){
/* The list is being searched and this trunk page is the page
** to allocate, regardless of whether it has leaves.
*/
*pPgno = iTrunk;
*ppPage = pTrunk;
searchList = 0;
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
if( k==0 ){
if( !pPrevTrunk ){
memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
}else{
rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
if( rc!=SQLITE_OK ){
goto end_allocate_page;
}
memcpy(&pPrevTrunk->aData[0], &pTrunk->aData[0], 4);
}
}else{
/* The trunk page is required by the caller but it contains
** pointers to free-list leaves. The first leaf becomes a trunk
** page in this case.
*/
MemPage *pNewTrunk;
Pgno iNewTrunk = get4byte(&pTrunk->aData[8]);
if( iNewTrunk>mxPage ){
rc = SQLITE_CORRUPT_BKPT;
goto end_allocate_page;
}
testcase( iNewTrunk==mxPage );
rc = btreeGetUnusedPage(pBt, iNewTrunk, &pNewTrunk, 0);
if( rc!=SQLITE_OK ){
goto end_allocate_page;
}
rc = sqlite3PagerWrite(pNewTrunk->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pNewTrunk);
goto end_allocate_page;
}
memcpy(&pNewTrunk->aData[0], &pTrunk->aData[0], 4);
put4byte(&pNewTrunk->aData[4], k-1);
memcpy(&pNewTrunk->aData[8], &pTrunk->aData[12], (k-1)*4);
releasePage(pNewTrunk);
if( !pPrevTrunk ){
assert( sqlite3PagerIswriteable(pPage1->pDbPage) );
put4byte(&pPage1->aData[32], iNewTrunk);
}else{
rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
if( rc ){
goto end_allocate_page;
}
put4byte(&pPrevTrunk->aData[0], iNewTrunk);
}
}
pTrunk = 0;
TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
#endif
}else if( k>0 ){
/* Extract a leaf from the trunk */
u32 closest;
Pgno iPage;
unsigned char *aData = pTrunk->aData;
if( nearby>0 ){
u32 i;
closest = 0;
if( eMode==BTALLOC_LE ){
for(i=0; i<k; i++){
iPage = get4byte(&aData[8+i*4]);
if( iPage<=nearby ){
closest = i;
break;
}
}
}else{
int dist;
dist = sqlite3AbsInt32(get4byte(&aData[8]) - nearby);
for(i=1; i<k; i++){
int d2 = sqlite3AbsInt32(get4byte(&aData[8+i*4]) - nearby);
if( d2<dist ){
closest = i;
dist = d2;
}
}
}
}else{
closest = 0;
}
iPage = get4byte(&aData[8+closest*4]);
testcase( iPage==mxPage );
if( iPage>mxPage ){
rc = SQLITE_CORRUPT_BKPT;
goto end_allocate_page;
}
testcase( iPage==mxPage );
if( !searchList
|| (iPage==nearby || (iPage<nearby && eMode==BTALLOC_LE))
){
int noContent;
*pPgno = iPage;
TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d"
": %d more free pages\n",
*pPgno, closest+1, k, pTrunk->pgno, n-1));
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc ) goto end_allocate_page;
if( closest<k-1 ){
memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
}
put4byte(&aData[4], k-1);
noContent = !btreeGetHasContent(pBt, *pPgno)? PAGER_GET_NOCONTENT : 0;
rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, noContent);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
*ppPage = 0;
}
}
searchList = 0;
}
}
releasePage(pPrevTrunk);
pPrevTrunk = 0;
}while( searchList );
}else{
/* There are no pages on the freelist, so append a new page to the
** database image.
**
** Normally, new pages allocated by this block can be requested from the
** pager layer with the 'no-content' flag set. This prevents the pager
** from trying to read the pages content from disk. However, if the
** current transaction has already run one or more incremental-vacuum
** steps, then the page we are about to allocate may contain content
** that is required in the event of a rollback. In this case, do
** not set the no-content flag. This causes the pager to load and journal
** the current page content before overwriting it.
**
** Note that the pager will not actually attempt to load or journal
** content for any page that really does lie past the end of the database
** file on disk. So the effects of disabling the no-content optimization
** here are confined to those pages that lie between the end of the
** database image and the end of the database file.
*/
int bNoContent = (0==IfNotOmitAV(pBt->bDoTruncate))? PAGER_GET_NOCONTENT:0;
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
if( rc ) return rc;
pBt->nPage++;
if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ) pBt->nPage++;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, pBt->nPage) ){
/* If *pPgno refers to a pointer-map page, allocate two new pages
** at the end of the file instead of one. The first allocated page
** becomes a new pointer-map page, the second is used by the caller.
*/
MemPage *pPg = 0;
TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", pBt->nPage));
assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
rc = btreeGetUnusedPage(pBt, pBt->nPage, &pPg, bNoContent);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pPg->pDbPage);
releasePage(pPg);
}
if( rc ) return rc;
pBt->nPage++;
if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ){ pBt->nPage++; }
}
#endif
put4byte(28 + (u8*)pBt->pPage1->aData, pBt->nPage);
*pPgno = pBt->nPage;
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, bNoContent);
if( rc ) return rc;
rc = sqlite3PagerWrite((*ppPage)->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(*ppPage);
*ppPage = 0;
}
TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
}
assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
end_allocate_page:
releasePage(pTrunk);
releasePage(pPrevTrunk);
assert( rc!=SQLITE_OK || sqlite3PagerPageRefcount((*ppPage)->pDbPage)<=1 );
assert( rc!=SQLITE_OK || (*ppPage)->isInit==0 );
return rc;
}
/*
** This function is used to add page iPage to the database file free-list.
** It is assumed that the page is not already a part of the free-list.
**
** The value passed as the second argument to this function is optional.
** If the caller happens to have a pointer to the MemPage object
** corresponding to page iPage handy, it may pass it as the second value.
** Otherwise, it may pass NULL.
**
** If a pointer to a MemPage object is passed as the second argument,
** its reference count is not altered by this function.
*/
static int freePage2(BtShared *pBt, MemPage *pMemPage, Pgno iPage){
MemPage *pTrunk = 0; /* Free-list trunk page */
Pgno iTrunk = 0; /* Page number of free-list trunk page */
MemPage *pPage1 = pBt->pPage1; /* Local reference to page 1 */
MemPage *pPage; /* Page being freed. May be NULL. */
int rc; /* Return Code */
int nFree; /* Initial number of pages on free-list */
assert( sqlite3_mutex_held(pBt->mutex) );
assert( CORRUPT_DB || iPage>1 );
assert( !pMemPage || pMemPage->pgno==iPage );
if( iPage<2 ) return SQLITE_CORRUPT_BKPT;
if( pMemPage ){
pPage = pMemPage;
sqlite3PagerRef(pPage->pDbPage);
}else{
pPage = btreePageLookup(pBt, iPage);
}
/* Increment the free page count on pPage1 */
rc = sqlite3PagerWrite(pPage1->pDbPage);
if( rc ) goto freepage_out;
nFree = get4byte(&pPage1->aData[36]);
put4byte(&pPage1->aData[36], nFree+1);
if( pBt->btsFlags & BTS_SECURE_DELETE ){
/* If the secure_delete option is enabled, then
** always fully overwrite deleted information with zeros.
*/
if( (!pPage && ((rc = btreeGetPage(pBt, iPage, &pPage, 0))!=0) )
|| ((rc = sqlite3PagerWrite(pPage->pDbPage))!=0)
){
goto freepage_out;
}
memset(pPage->aData, 0, pPage->pBt->pageSize);
}
/* If the database supports auto-vacuum, write an entry in the pointer-map
** to indicate that the page is free.
*/
if( ISAUTOVACUUM ){
ptrmapPut(pBt, iPage, PTRMAP_FREEPAGE, 0, &rc);
if( rc ) goto freepage_out;
}
/* Now manipulate the actual database free-list structure. There are two
** possibilities. If the free-list is currently empty, or if the first
** trunk page in the free-list is full, then this page will become a
** new free-list trunk page. Otherwise, it will become a leaf of the
** first trunk page in the current free-list. This block tests if it
** is possible to add the page as a new free-list leaf.
*/
if( nFree!=0 ){
u32 nLeaf; /* Initial number of leaf cells on trunk page */
iTrunk = get4byte(&pPage1->aData[32]);
rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
if( rc!=SQLITE_OK ){
goto freepage_out;
}
nLeaf = get4byte(&pTrunk->aData[4]);
assert( pBt->usableSize>32 );
if( nLeaf > (u32)pBt->usableSize/4 - 2 ){
rc = SQLITE_CORRUPT_BKPT;
goto freepage_out;
}
if( nLeaf < (u32)pBt->usableSize/4 - 8 ){
/* In this case there is room on the trunk page to insert the page
** being freed as a new leaf.
**
** Note that the trunk page is not really full until it contains
** usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
** coded. But due to a coding error in versions of SQLite prior to
** 3.6.0, databases with freelist trunk pages holding more than
** usableSize/4 - 8 entries will be reported as corrupt. In order
** to maintain backwards compatibility with older versions of SQLite,
** we will continue to restrict the number of entries to usableSize/4 - 8
** for now. At some point in the future (once everyone has upgraded
** to 3.6.0 or later) we should consider fixing the conditional above
** to read "usableSize/4-2" instead of "usableSize/4-8".
**
** EVIDENCE-OF: R-19920-11576 However, newer versions of SQLite still
** avoid using the last six entries in the freelist trunk page array in
** order that database files created by newer versions of SQLite can be
** read by older versions of SQLite.
*/
rc = sqlite3PagerWrite(pTrunk->pDbPage);
if( rc==SQLITE_OK ){
put4byte(&pTrunk->aData[4], nLeaf+1);
put4byte(&pTrunk->aData[8+nLeaf*4], iPage);
if( pPage && (pBt->btsFlags & BTS_SECURE_DELETE)==0 ){
sqlite3PagerDontWrite(pPage->pDbPage);
}
rc = btreeSetHasContent(pBt, iPage);
}
TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
goto freepage_out;
}
}
/* If control flows to this point, then it was not possible to add the
** the page being freed as a leaf page of the first trunk in the free-list.
** Possibly because the free-list is empty, or possibly because the
** first trunk in the free-list is full. Either way, the page being freed
** will become the new first trunk page in the free-list.
*/
if( pPage==0 && SQLITE_OK!=(rc = btreeGetPage(pBt, iPage, &pPage, 0)) ){
goto freepage_out;
}
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc!=SQLITE_OK ){
goto freepage_out;
}
put4byte(pPage->aData, iTrunk);
put4byte(&pPage->aData[4], 0);
put4byte(&pPage1->aData[32], iPage);
TRACE(("FREE-PAGE: %d new trunk page replacing %d\n", pPage->pgno, iTrunk));
freepage_out:
if( pPage ){
pPage->isInit = 0;
}
releasePage(pPage);
releasePage(pTrunk);
return rc;
}
static void freePage(MemPage *pPage, int *pRC){
if( (*pRC)==SQLITE_OK ){
*pRC = freePage2(pPage->pBt, pPage, pPage->pgno);
}
}
/*
** Free any overflow pages associated with the given Cell. Write the
** local Cell size (the number of bytes on the original page, omitting
** overflow) into *pnSize.
*/
static int clearCell(
MemPage *pPage, /* The page that contains the Cell */
unsigned char *pCell, /* First byte of the Cell */
u16 *pnSize /* Write the size of the Cell here */
){
BtShared *pBt = pPage->pBt;
CellInfo info;
Pgno ovflPgno;
int rc;
int nOvfl;
u32 ovflPageSize;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
pPage->xParseCell(pPage, pCell, &info);
*pnSize = info.nSize;
if( info.nLocal==info.nPayload ){
return SQLITE_OK; /* No overflow pages. Return without doing anything */
}
if( pCell+info.nSize-1 > pPage->aData+pPage->maskPage ){
return SQLITE_CORRUPT_BKPT; /* Cell extends past end of page */
}
ovflPgno = get4byte(pCell + info.nSize - 4);
assert( pBt->usableSize > 4 );
ovflPageSize = pBt->usableSize - 4;
nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
assert( nOvfl>0 ||
(CORRUPT_DB && (info.nPayload + ovflPageSize)<ovflPageSize)
);
while( nOvfl-- ){
Pgno iNext = 0;
MemPage *pOvfl = 0;
if( ovflPgno<2 || ovflPgno>btreePagecount(pBt) ){
/* 0 is not a legal page number and page 1 cannot be an
** overflow page. Therefore if ovflPgno<2 or past the end of the
** file the database must be corrupt. */
return SQLITE_CORRUPT_BKPT;
}
if( nOvfl ){
rc = getOverflowPage(pBt, ovflPgno, &pOvfl, &iNext);
if( rc ) return rc;
}
if( ( pOvfl || ((pOvfl = btreePageLookup(pBt, ovflPgno))!=0) )
&& sqlite3PagerPageRefcount(pOvfl->pDbPage)!=1
){
/* There is no reason any cursor should have an outstanding reference
** to an overflow page belonging to a cell that is being deleted/updated.
** So if there exists more than one reference to this page, then it
** must not really be an overflow page and the database must be corrupt.
** It is helpful to detect this before calling freePage2(), as
** freePage2() may zero the page contents if secure-delete mode is
** enabled. If this 'overflow' page happens to be a page that the
** caller is iterating through or using in some other way, this
** can be problematic.
*/
rc = SQLITE_CORRUPT_BKPT;
}else{
rc = freePage2(pBt, pOvfl, ovflPgno);
}
if( pOvfl ){
sqlite3PagerUnref(pOvfl->pDbPage);
}
if( rc ) return rc;
ovflPgno = iNext;
}
return SQLITE_OK;
}
/*
** Create the byte sequence used to represent a cell on page pPage
** and write that byte sequence into pCell[]. Overflow pages are
** allocated and filled in as necessary. The calling procedure
** is responsible for making sure sufficient space has been allocated
** for pCell[].
**
** Note that pCell does not necessary need to point to the pPage->aData
** area. pCell might point to some temporary storage. The cell will
** be constructed in this temporary area then copied into pPage->aData
** later.
*/
static int fillInCell(
MemPage *pPage, /* The page that contains the cell */
unsigned char *pCell, /* Complete text of the cell */
const BtreePayload *pX, /* Payload with which to construct the cell */
int *pnSize /* Write cell size here */
){
int nPayload;
const u8 *pSrc;
int nSrc, n, rc;
int spaceLeft;
MemPage *pOvfl = 0;
MemPage *pToRelease = 0;
unsigned char *pPrior;
unsigned char *pPayload;
BtShared *pBt = pPage->pBt;
Pgno pgnoOvfl = 0;
int nHeader;
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
/* pPage is not necessarily writeable since pCell might be auxiliary
** buffer space that is separate from the pPage buffer area */
assert( pCell<pPage->aData || pCell>=&pPage->aData[pBt->pageSize]
|| sqlite3PagerIswriteable(pPage->pDbPage) );
/* Fill in the header. */
nHeader = pPage->childPtrSize;
if( pPage->intKey ){
nPayload = pX->nData + pX->nZero;
pSrc = pX->pData;
nSrc = pX->nData;
assert( pPage->intKeyLeaf ); /* fillInCell() only called for leaves */
nHeader += putVarint32(&pCell[nHeader], nPayload);
nHeader += putVarint(&pCell[nHeader], *(u64*)&pX->nKey);
}else{
assert( pX->nKey<=0x7fffffff && pX->pKey!=0 );
nSrc = nPayload = (int)pX->nKey;
pSrc = pX->pKey;
nHeader += putVarint32(&pCell[nHeader], nPayload);
}
/* Fill in the payload */
if( nPayload<=pPage->maxLocal ){
n = nHeader + nPayload;
testcase( n==3 );
testcase( n==4 );
if( n<4 ) n = 4;
*pnSize = n;
spaceLeft = nPayload;
pPrior = pCell;
}else{
int mn = pPage->minLocal;
n = mn + (nPayload - mn) % (pPage->pBt->usableSize - 4);
testcase( n==pPage->maxLocal );
testcase( n==pPage->maxLocal+1 );
if( n > pPage->maxLocal ) n = mn;
spaceLeft = n;
*pnSize = n + nHeader + 4;
pPrior = &pCell[nHeader+n];
}
pPayload = &pCell[nHeader];
/* At this point variables should be set as follows:
**
** nPayload Total payload size in bytes
** pPayload Begin writing payload here
** spaceLeft Space available at pPayload. If nPayload>spaceLeft,
** that means content must spill into overflow pages.
** *pnSize Size of the local cell (not counting overflow pages)
** pPrior Where to write the pgno of the first overflow page
**
** Use a call to btreeParseCellPtr() to verify that the values above
** were computed correctly.
*/
#if SQLITE_DEBUG
{
CellInfo info;
pPage->xParseCell(pPage, pCell, &info);
assert( nHeader==(int)(info.pPayload - pCell) );
assert( info.nKey==pX->nKey );
assert( *pnSize == info.nSize );
assert( spaceLeft == info.nLocal );
}
#endif
/* Write the payload into the local Cell and any extra into overflow pages */
while( nPayload>0 ){
if( spaceLeft==0 ){
#ifndef SQLITE_OMIT_AUTOVACUUM
Pgno pgnoPtrmap = pgnoOvfl; /* Overflow page pointer-map entry page */
if( pBt->autoVacuum ){
do{
pgnoOvfl++;
} while(
PTRMAP_ISPAGE(pBt, pgnoOvfl) || pgnoOvfl==PENDING_BYTE_PAGE(pBt)
);
}
#endif
rc = allocateBtreePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl, 0);
#ifndef SQLITE_OMIT_AUTOVACUUM
/* If the database supports auto-vacuum, and the second or subsequent
** overflow page is being allocated, add an entry to the pointer-map
** for that page now.
**
** If this is the first overflow page, then write a partial entry
** to the pointer-map. If we write nothing to this pointer-map slot,
** then the optimistic overflow chain processing in clearCell()
** may misinterpret the uninitialized values and delete the
** wrong pages from the database.
*/
if( pBt->autoVacuum && rc==SQLITE_OK ){
u8 eType = (pgnoPtrmap?PTRMAP_OVERFLOW2:PTRMAP_OVERFLOW1);
ptrmapPut(pBt, pgnoOvfl, eType, pgnoPtrmap, &rc);
if( rc ){
releasePage(pOvfl);
}
}
#endif
if( rc ){
releasePage(pToRelease);
return rc;
}
/* If pToRelease is not zero than pPrior points into the data area
** of pToRelease. Make sure pToRelease is still writeable. */
assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
/* If pPrior is part of the data area of pPage, then make sure pPage
** is still writeable */
assert( pPrior<pPage->aData || pPrior>=&pPage->aData[pBt->pageSize]
|| sqlite3PagerIswriteable(pPage->pDbPage) );
put4byte(pPrior, pgnoOvfl);
releasePage(pToRelease);
pToRelease = pOvfl;
pPrior = pOvfl->aData;
put4byte(pPrior, 0);
pPayload = &pOvfl->aData[4];
spaceLeft = pBt->usableSize - 4;
}
n = nPayload;
if( n>spaceLeft ) n = spaceLeft;
/* If pToRelease is not zero than pPayload points into the data area
** of pToRelease. Make sure pToRelease is still writeable. */
assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
/* If pPayload is part of the data area of pPage, then make sure pPage
** is still writeable */
assert( pPayload<pPage->aData || pPayload>=&pPage->aData[pBt->pageSize]
|| sqlite3PagerIswriteable(pPage->pDbPage) );
if( nSrc>0 ){
if( n>nSrc ) n = nSrc;
assert( pSrc );
memcpy(pPayload, pSrc, n);
}else{
memset(pPayload, 0, n);
}
nPayload -= n;
pPayload += n;
pSrc += n;
nSrc -= n;
spaceLeft -= n;
}
releasePage(pToRelease);
return SQLITE_OK;
}
/*
** Remove the i-th cell from pPage. This routine effects pPage only.
** The cell content is not freed or deallocated. It is assumed that
** the cell content has been copied someplace else. This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
*/
static void dropCell(MemPage *pPage, int idx, int sz, int *pRC){
u32 pc; /* Offset to cell content of cell being deleted */
u8 *data; /* pPage->aData */
u8 *ptr; /* Used to move bytes around within data[] */
int rc; /* The return code */
int hdr; /* Beginning of the header. 0 most pages. 100 page 1 */
if( *pRC ) return;
assert( idx>=0 && idx<pPage->nCell );
assert( CORRUPT_DB || sz==cellSize(pPage, idx) );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
data = pPage->aData;
ptr = &pPage->aCellIdx[2*idx];
pc = get2byte(ptr);
hdr = pPage->hdrOffset;
testcase( pc==get2byte(&data[hdr+5]) );
testcase( pc+sz==pPage->pBt->usableSize );
if( pc < (u32)get2byte(&data[hdr+5]) || pc+sz > pPage->pBt->usableSize ){
*pRC = SQLITE_CORRUPT_BKPT;
return;
}
rc = freeSpace(pPage, pc, sz);
if( rc ){
*pRC = rc;
return;
}
pPage->nCell--;
if( pPage->nCell==0 ){
memset(&data[hdr+1], 0, 4);
data[hdr+7] = 0;
put2byte(&data[hdr+5], pPage->pBt->usableSize);
pPage->nFree = pPage->pBt->usableSize - pPage->hdrOffset
- pPage->childPtrSize - 8;
}else{
memmove(ptr, ptr+2, 2*(pPage->nCell - idx));
put2byte(&data[hdr+3], pPage->nCell);
pPage->nFree += 2;
}
}
/*
** Insert a new cell on pPage at cell index "i". pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there. If it
** will not fit, then make a copy of the cell content into pTemp if
** pTemp is not null. Regardless of pTemp, allocate a new entry
** in pPage->apOvfl[] and make it point to the cell content (either
** in pTemp or the original pCell) and also record its index.
** Allocating a new entry in pPage->aCell[] implies that
** pPage->nOverflow is incremented.
**
** *pRC must be SQLITE_OK when this routine is called.
*/
static void insertCell(
MemPage *pPage, /* Page into which we are copying */
int i, /* New cell becomes the i-th cell of the page */
u8 *pCell, /* Content of the new cell */
int sz, /* Bytes of content in pCell */
u8 *pTemp, /* Temp storage space for pCell, if needed */
Pgno iChild, /* If non-zero, replace first 4 bytes with this value */
int *pRC /* Read and write return code from here */
){
int idx = 0; /* Where to write new cell content in data[] */
int j; /* Loop counter */
u8 *data; /* The content of the whole page */
u8 *pIns; /* The point in pPage->aCellIdx[] where no cell inserted */
assert( *pRC==SQLITE_OK );
assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
assert( MX_CELL(pPage->pBt)<=10921 );
assert( pPage->nCell<=MX_CELL(pPage->pBt) || CORRUPT_DB );
assert( pPage->nOverflow<=ArraySize(pPage->apOvfl) );
assert( ArraySize(pPage->apOvfl)==ArraySize(pPage->aiOvfl) );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
/* The cell should normally be sized correctly. However, when moving a
** malformed cell from a leaf page to an interior page, if the cell size
** wanted to be less than 4 but got rounded up to 4 on the leaf, then size
** might be less than 8 (leaf-size + pointer) on the interior node. Hence
** the term after the || in the following assert(). */
assert( sz==pPage->xCellSize(pPage, pCell) || (sz==8 && iChild>0) );
if( pPage->nOverflow || sz+2>pPage->nFree ){
if( pTemp ){
memcpy(pTemp, pCell, sz);
pCell = pTemp;
}
if( iChild ){
put4byte(pCell, iChild);
}
j = pPage->nOverflow++;
assert( j<(int)(sizeof(pPage->apOvfl)/sizeof(pPage->apOvfl[0])) );
pPage->apOvfl[j] = pCell;
pPage->aiOvfl[j] = (u16)i;
/* When multiple overflows occur, they are always sequential and in
** sorted order. This invariants arise because multiple overflows can
** only occur when inserting divider cells into the parent page during
** balancing, and the dividers are adjacent and sorted.
*/
assert( j==0 || pPage->aiOvfl[j-1]<(u16)i ); /* Overflows in sorted order */
assert( j==0 || i==pPage->aiOvfl[j-1]+1 ); /* Overflows are sequential */
}else{
int rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc!=SQLITE_OK ){
*pRC = rc;
return;
}
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
data = pPage->aData;
assert( &data[pPage->cellOffset]==pPage->aCellIdx );
rc = allocateSpace(pPage, sz, &idx);
if( rc ){ *pRC = rc; return; }
/* The allocateSpace() routine guarantees the following properties
** if it returns successfully */
assert( idx >= 0 );
assert( idx >= pPage->cellOffset+2*pPage->nCell+2 || CORRUPT_DB );
assert( idx+sz <= (int)pPage->pBt->usableSize );
pPage->nFree -= (u16)(2 + sz);
memcpy(&data[idx], pCell, sz);
if( iChild ){
put4byte(&data[idx], iChild);
}
pIns = pPage->aCellIdx + i*2;
memmove(pIns+2, pIns, 2*(pPage->nCell - i));
put2byte(pIns, idx);
pPage->nCell++;
/* increment the cell count */
if( (++data[pPage->hdrOffset+4])==0 ) data[pPage->hdrOffset+3]++;
assert( get2byte(&data[pPage->hdrOffset+3])==pPage->nCell );
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pPage->pBt->autoVacuum ){
/* The cell may contain a pointer to an overflow page. If so, write
** the entry for the overflow page into the pointer map.
*/
ptrmapPutOvflPtr(pPage, pCell, pRC);
}
#endif
}
}
/*
** A CellArray object contains a cache of pointers and sizes for a
** consecutive sequence of cells that might be held on multiple pages.
*/
typedef struct CellArray CellArray;
struct CellArray {
int nCell; /* Number of cells in apCell[] */
MemPage *pRef; /* Reference page */
u8 **apCell; /* All cells begin balanced */
u16 *szCell; /* Local size of all cells in apCell[] */
};
/*
** Make sure the cell sizes at idx, idx+1, ..., idx+N-1 have been
** computed.
*/
static void populateCellCache(CellArray *p, int idx, int N){
assert( idx>=0 && idx+N<=p->nCell );
while( N>0 ){
assert( p->apCell[idx]!=0 );
if( p->szCell[idx]==0 ){
p->szCell[idx] = p->pRef->xCellSize(p->pRef, p->apCell[idx]);
}else{
assert( CORRUPT_DB ||
p->szCell[idx]==p->pRef->xCellSize(p->pRef, p->apCell[idx]) );
}
idx++;
N--;
}
}
/*
** Return the size of the Nth element of the cell array
*/
static SQLITE_NOINLINE u16 computeCellSize(CellArray *p, int N){
assert( N>=0 && N<p->nCell );
assert( p->szCell[N]==0 );
p->szCell[N] = p->pRef->xCellSize(p->pRef, p->apCell[N]);
return p->szCell[N];
}
static u16 cachedCellSize(CellArray *p, int N){
assert( N>=0 && N<p->nCell );
if( p->szCell[N] ) return p->szCell[N];
return computeCellSize(p, N);
}
/*
** Array apCell[] contains pointers to nCell b-tree page cells. The
** szCell[] array contains the size in bytes of each cell. This function
** replaces the current contents of page pPg with the contents of the cell
** array.
**
** Some of the cells in apCell[] may currently be stored in pPg. This
** function works around problems caused by this by making a copy of any
** such cells before overwriting the page data.
**
** The MemPage.nFree field is invalidated by this function. It is the
** responsibility of the caller to set it correctly.
*/
static int rebuildPage(
MemPage *pPg, /* Edit this page */
int nCell, /* Final number of cells on page */
u8 **apCell, /* Array of cells */
u16 *szCell /* Array of cell sizes */
){
const int hdr = pPg->hdrOffset; /* Offset of header on pPg */
u8 * const aData = pPg->aData; /* Pointer to data for pPg */
const int usableSize = pPg->pBt->usableSize;
u8 * const pEnd = &aData[usableSize];
int i;
u8 *pCellptr = pPg->aCellIdx;
u8 *pTmp = sqlite3PagerTempSpace(pPg->pBt->pPager);
u8 *pData;
i = get2byte(&aData[hdr+5]);
memcpy(&pTmp[i], &aData[i], usableSize - i);
pData = pEnd;
for(i=0; i<nCell; i++){
u8 *pCell = apCell[i];
if( SQLITE_WITHIN(pCell,aData,pEnd) ){
pCell = &pTmp[pCell - aData];
}
pData -= szCell[i];
put2byte(pCellptr, (pData - aData));
pCellptr += 2;
if( pData < pCellptr ) return SQLITE_CORRUPT_BKPT;
memcpy(pData, pCell, szCell[i]);
assert( szCell[i]==pPg->xCellSize(pPg, pCell) || CORRUPT_DB );
testcase( szCell[i]!=pPg->xCellSize(pPg,pCell) );
}
/* The pPg->nFree field is now set incorrectly. The caller will fix it. */
pPg->nCell = nCell;
pPg->nOverflow = 0;
put2byte(&aData[hdr+1], 0);
put2byte(&aData[hdr+3], pPg->nCell);
put2byte(&aData[hdr+5], pData - aData);
aData[hdr+7] = 0x00;
return SQLITE_OK;
}
/*
** Array apCell[] contains nCell pointers to b-tree cells. Array szCell
** contains the size in bytes of each such cell. This function attempts to
** add the cells stored in the array to page pPg. If it cannot (because
** the page needs to be defragmented before the cells will fit), non-zero
** is returned. Otherwise, if the cells are added successfully, zero is
** returned.
**
** Argument pCellptr points to the first entry in the cell-pointer array
** (part of page pPg) to populate. After cell apCell[0] is written to the
** page body, a 16-bit offset is written to pCellptr. And so on, for each
** cell in the array. It is the responsibility of the caller to ensure
** that it is safe to overwrite this part of the cell-pointer array.
**
** When this function is called, *ppData points to the start of the
** content area on page pPg. If the size of the content area is extended,
** *ppData is updated to point to the new start of the content area
** before returning.
**
** Finally, argument pBegin points to the byte immediately following the
** end of the space required by this page for the cell-pointer area (for
** all cells - not just those inserted by the current call). If the content
** area must be extended to before this point in order to accomodate all
** cells in apCell[], then the cells do not fit and non-zero is returned.
*/
static int pageInsertArray(
MemPage *pPg, /* Page to add cells to */
u8 *pBegin, /* End of cell-pointer array */
u8 **ppData, /* IN/OUT: Page content -area pointer */
u8 *pCellptr, /* Pointer to cell-pointer area */
int iFirst, /* Index of first cell to add */
int nCell, /* Number of cells to add to pPg */
CellArray *pCArray /* Array of cells */
){
int i;
u8 *aData = pPg->aData;
u8 *pData = *ppData;
int iEnd = iFirst + nCell;
assert( CORRUPT_DB || pPg->hdrOffset==0 ); /* Never called on page 1 */
for(i=iFirst; i<iEnd; i++){
int sz, rc;
u8 *pSlot;
sz = cachedCellSize(pCArray, i);
if( (aData[1]==0 && aData[2]==0) || (pSlot = pageFindSlot(pPg,sz,&rc))==0 ){
if( (pData - pBegin)<sz ) return 1;
pData -= sz;
pSlot = pData;
}
/* pSlot and pCArray->apCell[i] will never overlap on a well-formed
** database. But they might for a corrupt database. Hence use memmove()
** since memcpy() sends SIGABORT with overlapping buffers on OpenBSD */
assert( (pSlot+sz)<=pCArray->apCell[i]
|| pSlot>=(pCArray->apCell[i]+sz)
|| CORRUPT_DB );
memmove(pSlot, pCArray->apCell[i], sz);
put2byte(pCellptr, (pSlot - aData));
pCellptr += 2;
}
*ppData = pData;
return 0;
}
/*
** Array apCell[] contains nCell pointers to b-tree cells. Array szCell
** contains the size in bytes of each such cell. This function adds the
** space associated with each cell in the array that is currently stored
** within the body of pPg to the pPg free-list. The cell-pointers and other
** fields of the page are not updated.
**
** This function returns the total number of cells added to the free-list.
*/
static int pageFreeArray(
MemPage *pPg, /* Page to edit */
int iFirst, /* First cell to delete */
int nCell, /* Cells to delete */
CellArray *pCArray /* Array of cells */
){
u8 * const aData = pPg->aData;
u8 * const pEnd = &aData[pPg->pBt->usableSize];
u8 * const pStart = &aData[pPg->hdrOffset + 8 + pPg->childPtrSize];
int nRet = 0;
int i;
int iEnd = iFirst + nCell;
u8 *pFree = 0;
int szFree = 0;
for(i=iFirst; i<iEnd; i++){
u8 *pCell = pCArray->apCell[i];
if( SQLITE_WITHIN(pCell, pStart, pEnd) ){
int sz;
/* No need to use cachedCellSize() here. The sizes of all cells that
** are to be freed have already been computing while deciding which
** cells need freeing */
sz = pCArray->szCell[i]; assert( sz>0 );
if( pFree!=(pCell + sz) ){
if( pFree ){
assert( pFree>aData && (pFree - aData)<65536 );
freeSpace(pPg, (u16)(pFree - aData), szFree);
}
pFree = pCell;
szFree = sz;
if( pFree+sz>pEnd ) return 0;
}else{
pFree = pCell;
szFree += sz;
}
nRet++;
}
}
if( pFree ){
assert( pFree>aData && (pFree - aData)<65536 );
freeSpace(pPg, (u16)(pFree - aData), szFree);
}
return nRet;
}
/*
** apCell[] and szCell[] contains pointers to and sizes of all cells in the
** pages being balanced. The current page, pPg, has pPg->nCell cells starting
** with apCell[iOld]. After balancing, this page should hold nNew cells
** starting at apCell[iNew].
**
** This routine makes the necessary adjustments to pPg so that it contains
** the correct cells after being balanced.
**
** The pPg->nFree field is invalid when this function returns. It is the
** responsibility of the caller to set it correctly.
*/
static int editPage(
MemPage *pPg, /* Edit this page */
int iOld, /* Index of first cell currently on page */
int iNew, /* Index of new first cell on page */
int nNew, /* Final number of cells on page */
CellArray *pCArray /* Array of cells and sizes */
){
u8 * const aData = pPg->aData;
const int hdr = pPg->hdrOffset;
u8 *pBegin = &pPg->aCellIdx[nNew * 2];
int nCell = pPg->nCell; /* Cells stored on pPg */
u8 *pData;
u8 *pCellptr;
int i;
int iOldEnd = iOld + pPg->nCell + pPg->nOverflow;
int iNewEnd = iNew + nNew;
#ifdef SQLITE_DEBUG
u8 *pTmp = sqlite3PagerTempSpace(pPg->pBt->pPager);
memcpy(pTmp, aData, pPg->pBt->usableSize);
#endif
/* Remove cells from the start and end of the page */
if( iOld<iNew ){
int nShift = pageFreeArray(pPg, iOld, iNew-iOld, pCArray);
memmove(pPg->aCellIdx, &pPg->aCellIdx[nShift*2], nCell*2);
nCell -= nShift;
}
if( iNewEnd < iOldEnd ){
nCell -= pageFreeArray(pPg, iNewEnd, iOldEnd - iNewEnd, pCArray);
}
pData = &aData[get2byteNotZero(&aData[hdr+5])];
if( pData<pBegin ) goto editpage_fail;
/* Add cells to the start of the page */
if( iNew<iOld ){
int nAdd = MIN(nNew,iOld-iNew);
assert( (iOld-iNew)<nNew || nCell==0 || CORRUPT_DB );
pCellptr = pPg->aCellIdx;
memmove(&pCellptr[nAdd*2], pCellptr, nCell*2);
if( pageInsertArray(
pPg, pBegin, &pData, pCellptr,
iNew, nAdd, pCArray
) ) goto editpage_fail;
nCell += nAdd;
}
/* Add any overflow cells */
for(i=0; i<pPg->nOverflow; i++){
int iCell = (iOld + pPg->aiOvfl[i]) - iNew;
if( iCell>=0 && iCell<nNew ){
pCellptr = &pPg->aCellIdx[iCell * 2];
memmove(&pCellptr[2], pCellptr, (nCell - iCell) * 2);
nCell++;
if( pageInsertArray(
pPg, pBegin, &pData, pCellptr,
iCell+iNew, 1, pCArray
) ) goto editpage_fail;
}
}
/* Append cells to the end of the page */
pCellptr = &pPg->aCellIdx[nCell*2];
if( pageInsertArray(
pPg, pBegin, &pData, pCellptr,
iNew+nCell, nNew-nCell, pCArray
) ) goto editpage_fail;
pPg->nCell = nNew;
pPg->nOverflow = 0;
put2byte(&aData[hdr+3], pPg->nCell);
put2byte(&aData[hdr+5], pData - aData);
#ifdef SQLITE_DEBUG
for(i=0; i<nNew && !CORRUPT_DB; i++){
u8 *pCell = pCArray->apCell[i+iNew];
int iOff = get2byteAligned(&pPg->aCellIdx[i*2]);
if( SQLITE_WITHIN(pCell, aData, &aData[pPg->pBt->usableSize]) ){
pCell = &pTmp[pCell - aData];
}
assert( 0==memcmp(pCell, &aData[iOff],
pCArray->pRef->xCellSize(pCArray->pRef, pCArray->apCell[i+iNew])) );
}
#endif
return SQLITE_OK;
editpage_fail:
/* Unable to edit this page. Rebuild it from scratch instead. */
populateCellCache(pCArray, iNew, nNew);
return rebuildPage(pPg, nNew, &pCArray->apCell[iNew], &pCArray->szCell[iNew]);
}
/*
** The following parameters determine how many adjacent pages get involved
** in a balancing operation. NN is the number of neighbors on either side
** of the page that participate in the balancing operation. NB is the
** total number of pages that participate, including the target page and
** NN neighbors on either side.
**
** The minimum value of NN is 1 (of course). Increasing NN above 1
** (to 2 or 3) gives a modest improvement in SELECT and DELETE performance
** in exchange for a larger degradation in INSERT and UPDATE performance.
** The value of NN appears to give the best results overall.
*/
#define NN 1 /* Number of neighbors on either side of pPage */
#define NB (NN*2+1) /* Total pages involved in the balance */
#ifndef SQLITE_OMIT_QUICKBALANCE
/*
** This version of balance() handles the common special case where
** a new entry is being inserted on the extreme right-end of the
** tree, in other words, when the new entry will become the largest
** entry in the tree.
**
** Instead of trying to balance the 3 right-most leaf pages, just add
** a new page to the right-hand side and put the one new entry in
** that page. This leaves the right side of the tree somewhat
** unbalanced. But odds are that we will be inserting new entries
** at the end soon afterwards so the nearly empty page will quickly
** fill up. On average.
**
** pPage is the leaf page which is the right-most page in the tree.
** pParent is its parent. pPage must have a single overflow entry
** which is also the right-most entry on the page.
**
** The pSpace buffer is used to store a temporary copy of the divider
** cell that will be inserted into pParent. Such a cell consists of a 4
** byte page number followed by a variable length integer. In other
** words, at most 13 bytes. Hence the pSpace buffer must be at
** least 13 bytes in size.
*/
static int balance_quick(MemPage *pParent, MemPage *pPage, u8 *pSpace){
BtShared *const pBt = pPage->pBt; /* B-Tree Database */
MemPage *pNew; /* Newly allocated page */
int rc; /* Return Code */
Pgno pgnoNew; /* Page number of pNew */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
assert( pPage->nOverflow==1 );
/* This error condition is now caught prior to reaching this function */
if( NEVER(pPage->nCell==0) ) return SQLITE_CORRUPT_BKPT;
/* Allocate a new page. This page will become the right-sibling of
** pPage. Make the parent page writable, so that the new divider cell
** may be inserted. If both these operations are successful, proceed.
*/
rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
if( rc==SQLITE_OK ){
u8 *pOut = &pSpace[4];
u8 *pCell = pPage->apOvfl[0];
u16 szCell = pPage->xCellSize(pPage, pCell);
u8 *pStop;
assert( sqlite3PagerIswriteable(pNew->pDbPage) );
assert( pPage->aData[0]==(PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF) );
zeroPage(pNew, PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF);
rc = rebuildPage(pNew, 1, &pCell, &szCell);
if( NEVER(rc) ) return rc;
pNew->nFree = pBt->usableSize - pNew->cellOffset - 2 - szCell;
/* If this is an auto-vacuum database, update the pointer map
** with entries for the new page, and any pointer from the
** cell on the page to an overflow page. If either of these
** operations fails, the return code is set, but the contents
** of the parent page are still manipulated by thh code below.
** That is Ok, at this point the parent page is guaranteed to
** be marked as dirty. Returning an error code will cause a
** rollback, undoing any changes made to the parent page.
*/
if( ISAUTOVACUUM ){
ptrmapPut(pBt, pgnoNew, PTRMAP_BTREE, pParent->pgno, &rc);
if( szCell>pNew->minLocal ){
ptrmapPutOvflPtr(pNew, pCell, &rc);
}
}
/* Create a divider cell to insert into pParent. The divider cell
** consists of a 4-byte page number (the page number of pPage) and
** a variable length key value (which must be the same value as the
** largest key on pPage).
**
** To find the largest key value on pPage, first find the right-most
** cell on pPage. The first two fields of this cell are the
** record-length (a variable length integer at most 32-bits in size)
** and the key value (a variable length integer, may have any value).
** The first of the while(...) loops below skips over the record-length
** field. The second while(...) loop copies the key value from the
** cell on pPage into the pSpace buffer.
*/
pCell = findCell(pPage, pPage->nCell-1);
pStop = &pCell[9];
while( (*(pCell++)&0x80) && pCell<pStop );
pStop = &pCell[9];
while( ((*(pOut++) = *(pCell++))&0x80) && pCell<pStop );
/* Insert the new divider cell into pParent. */
if( rc==SQLITE_OK ){
insertCell(pParent, pParent->nCell, pSpace, (int)(pOut-pSpace),
0, pPage->pgno, &rc);
}
/* Set the right-child pointer of pParent to point to the new page. */
put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew);
/* Release the reference to the new page. */
releasePage(pNew);
}
return rc;
}
#endif /* SQLITE_OMIT_QUICKBALANCE */
#if 0
/*
** This function does not contribute anything to the operation of SQLite.
** it is sometimes activated temporarily while debugging code responsible
** for setting pointer-map entries.
*/
static int ptrmapCheckPages(MemPage **apPage, int nPage){
int i, j;
for(i=0; i<nPage; i++){
Pgno n;
u8 e;
MemPage *pPage = apPage[i];
BtShared *pBt = pPage->pBt;
assert( pPage->isInit );
for(j=0; j<pPage->nCell; j++){
CellInfo info;
u8 *z;
z = findCell(pPage, j);
pPage->xParseCell(pPage, z, &info);
if( info.nLocal<info.nPayload ){
Pgno ovfl = get4byte(&z[info.nSize-4]);
ptrmapGet(pBt, ovfl, &e, &n);
assert( n==pPage->pgno && e==PTRMAP_OVERFLOW1 );
}
if( !pPage->leaf ){
Pgno child = get4byte(z);
ptrmapGet(pBt, child, &e, &n);
assert( n==pPage->pgno && e==PTRMAP_BTREE );
}
}
if( !pPage->leaf ){
Pgno child = get4byte(&pPage->aData[pPage->hdrOffset+8]);
ptrmapGet(pBt, child, &e, &n);
assert( n==pPage->pgno && e==PTRMAP_BTREE );
}
}
return 1;
}
#endif
/*
** This function is used to copy the contents of the b-tree node stored
** on page pFrom to page pTo. If page pFrom was not a leaf page, then
** the pointer-map entries for each child page are updated so that the
** parent page stored in the pointer map is page pTo. If pFrom contained
** any cells with overflow page pointers, then the corresponding pointer
** map entries are also updated so that the parent page is page pTo.
**
** If pFrom is currently carrying any overflow cells (entries in the
** MemPage.apOvfl[] array), they are not copied to pTo.
**
** Before returning, page pTo is reinitialized using btreeInitPage().
**
** The performance of this function is not critical. It is only used by
** the balance_shallower() and balance_deeper() procedures, neither of
** which are called often under normal circumstances.
*/
static void copyNodeContent(MemPage *pFrom, MemPage *pTo, int *pRC){
if( (*pRC)==SQLITE_OK ){
BtShared * const pBt = pFrom->pBt;
u8 * const aFrom = pFrom->aData;
u8 * const aTo = pTo->aData;
int const iFromHdr = pFrom->hdrOffset;
int const iToHdr = ((pTo->pgno==1) ? 100 : 0);
int rc;
int iData;
assert( pFrom->isInit );
assert( pFrom->nFree>=iToHdr );
assert( get2byte(&aFrom[iFromHdr+5]) <= (int)pBt->usableSize );
/* Copy the b-tree node content from page pFrom to page pTo. */
iData = get2byte(&aFrom[iFromHdr+5]);
memcpy(&aTo[iData], &aFrom[iData], pBt->usableSize-iData);
memcpy(&aTo[iToHdr], &aFrom[iFromHdr], pFrom->cellOffset + 2*pFrom->nCell);
/* Reinitialize page pTo so that the contents of the MemPage structure
** match the new data. The initialization of pTo can actually fail under
** fairly obscure circumstances, even though it is a copy of initialized
** page pFrom.
*/
pTo->isInit = 0;
rc = btreeInitPage(pTo);
if( rc!=SQLITE_OK ){
*pRC = rc;
return;
}
/* If this is an auto-vacuum database, update the pointer-map entries
** for any b-tree or overflow pages that pTo now contains the pointers to.
*/
if( ISAUTOVACUUM ){
*pRC = setChildPtrmaps(pTo);
}
}
}
/*
** This routine redistributes cells on the iParentIdx'th child of pParent
** (hereafter "the page") and up to 2 siblings so that all pages have about the
** same amount of free space. Usually a single sibling on either side of the
** page are used in the balancing, though both siblings might come from one
** side if the page is the first or last child of its parent. If the page
** has fewer than 2 siblings (something which can only happen if the page
** is a root page or a child of a root page) then all available siblings
** participate in the balancing.
**
** The number of siblings of the page might be increased or decreased by
** one or two in an effort to keep pages nearly full but not over full.
**
** Note that when this routine is called, some of the cells on the page
** might not actually be stored in MemPage.aData[]. This can happen
** if the page is overfull. This routine ensures that all cells allocated
** to the page and its siblings fit into MemPage.aData[] before returning.
**
** In the course of balancing the page and its siblings, cells may be
** inserted into or removed from the parent page (pParent). Doing so
** may cause the parent page to become overfull or underfull. If this
** happens, it is the responsibility of the caller to invoke the correct
** balancing routine to fix this problem (see the balance() routine).
**
** If this routine fails for any reason, it might leave the database
** in a corrupted state. So if this routine fails, the database should
** be rolled back.
**
** The third argument to this function, aOvflSpace, is a pointer to a
** buffer big enough to hold one page. If while inserting cells into the parent
** page (pParent) the parent page becomes overfull, this buffer is
** used to store the parent's overflow cells. Because this function inserts
** a maximum of four divider cells into the parent page, and the maximum
** size of a cell stored within an internal node is always less than 1/4
** of the page-size, the aOvflSpace[] buffer is guaranteed to be large
** enough for all overflow cells.
**
** If aOvflSpace is set to a null pointer, this function returns
** SQLITE_NOMEM.
*/
static int balance_nonroot(
MemPage *pParent, /* Parent page of siblings being balanced */
int iParentIdx, /* Index of "the page" in pParent */
u8 *aOvflSpace, /* page-size bytes of space for parent ovfl */
int isRoot, /* True if pParent is a root-page */
int bBulk /* True if this call is part of a bulk load */
){
BtShared *pBt; /* The whole database */
int nMaxCells = 0; /* Allocated size of apCell, szCell, aFrom. */
int nNew = 0; /* Number of pages in apNew[] */
int nOld; /* Number of pages in apOld[] */
int i, j, k; /* Loop counters */
int nxDiv; /* Next divider slot in pParent->aCell[] */
int rc = SQLITE_OK; /* The return code */
u16 leafCorrection; /* 4 if pPage is a leaf. 0 if not */
int leafData; /* True if pPage is a leaf of a LEAFDATA tree */
int usableSpace; /* Bytes in pPage beyond the header */
int pageFlags; /* Value of pPage->aData[0] */
int iSpace1 = 0; /* First unused byte of aSpace1[] */
int iOvflSpace = 0; /* First unused byte of aOvflSpace[] */
int szScratch; /* Size of scratch memory requested */
MemPage *apOld[NB]; /* pPage and up to two siblings */
MemPage *apNew[NB+2]; /* pPage and up to NB siblings after balancing */
u8 *pRight; /* Location in parent of right-sibling pointer */
u8 *apDiv[NB-1]; /* Divider cells in pParent */
int cntNew[NB+2]; /* Index in b.paCell[] of cell after i-th page */
int cntOld[NB+2]; /* Old index in b.apCell[] */
int szNew[NB+2]; /* Combined size of cells placed on i-th page */
u8 *aSpace1; /* Space for copies of dividers cells */
Pgno pgno; /* Temp var to store a page number in */
u8 abDone[NB+2]; /* True after i'th new page is populated */
Pgno aPgno[NB+2]; /* Page numbers of new pages before shuffling */
Pgno aPgOrder[NB+2]; /* Copy of aPgno[] used for sorting pages */
u16 aPgFlags[NB+2]; /* flags field of new pages before shuffling */
CellArray b; /* Parsed information on cells being balanced */
memset(abDone, 0, sizeof(abDone));
b.nCell = 0;
b.apCell = 0;
pBt = pParent->pBt;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
#if 0
TRACE(("BALANCE: begin page %d child of %d\n", pPage->pgno, pParent->pgno));
#endif
/* At this point pParent may have at most one overflow cell. And if
** this overflow cell is present, it must be the cell with
** index iParentIdx. This scenario comes about when this function
** is called (indirectly) from sqlite3BtreeDelete().
*/
assert( pParent->nOverflow==0 || pParent->nOverflow==1 );
assert( pParent->nOverflow==0 || pParent->aiOvfl[0]==iParentIdx );
if( !aOvflSpace ){
return SQLITE_NOMEM_BKPT;
}
/* Find the sibling pages to balance. Also locate the cells in pParent
** that divide the siblings. An attempt is made to find NN siblings on
** either side of pPage. More siblings are taken from one side, however,
** if there are fewer than NN siblings on the other side. If pParent
** has NB or fewer children then all children of pParent are taken.
**
** This loop also drops the divider cells from the parent page. This
** way, the remainder of the function does not have to deal with any
** overflow cells in the parent page, since if any existed they will
** have already been removed.
*/
i = pParent->nOverflow + pParent->nCell;
if( i<2 ){
nxDiv = 0;
}else{
assert( bBulk==0 || bBulk==1 );
if( iParentIdx==0 ){
nxDiv = 0;
}else if( iParentIdx==i ){
nxDiv = i-2+bBulk;
}else{
nxDiv = iParentIdx-1;
}
i = 2-bBulk;
}
nOld = i+1;
if( (i+nxDiv-pParent->nOverflow)==pParent->nCell ){
pRight = &pParent->aData[pParent->hdrOffset+8];
}else{
pRight = findCell(pParent, i+nxDiv-pParent->nOverflow);
}
pgno = get4byte(pRight);
while( 1 ){
rc = getAndInitPage(pBt, pgno, &apOld[i], 0, 0);
if( rc ){
memset(apOld, 0, (i+1)*sizeof(MemPage*));
goto balance_cleanup;
}
nMaxCells += 1+apOld[i]->nCell+apOld[i]->nOverflow;
if( (i--)==0 ) break;
if( i+nxDiv==pParent->aiOvfl[0] && pParent->nOverflow ){
apDiv[i] = pParent->apOvfl[0];
pgno = get4byte(apDiv[i]);
szNew[i] = pParent->xCellSize(pParent, apDiv[i]);
pParent->nOverflow = 0;
}else{
apDiv[i] = findCell(pParent, i+nxDiv-pParent->nOverflow);
pgno = get4byte(apDiv[i]);
szNew[i] = pParent->xCellSize(pParent, apDiv[i]);
/* Drop the cell from the parent page. apDiv[i] still points to
** the cell within the parent, even though it has been dropped.
** This is safe because dropping a cell only overwrites the first
** four bytes of it, and this function does not need the first
** four bytes of the divider cell. So the pointer is safe to use
** later on.
**
** But not if we are in secure-delete mode. In secure-delete mode,
** the dropCell() routine will overwrite the entire cell with zeroes.
** In this case, temporarily copy the cell into the aOvflSpace[]
** buffer. It will be copied out again as soon as the aSpace[] buffer
** is allocated. */
if( pBt->btsFlags & BTS_SECURE_DELETE ){
int iOff;
iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);
if( (iOff+szNew[i])>(int)pBt->usableSize ){
rc = SQLITE_CORRUPT_BKPT;
memset(apOld, 0, (i+1)*sizeof(MemPage*));
goto balance_cleanup;
}else{
memcpy(&aOvflSpace[iOff], apDiv[i], szNew[i]);
apDiv[i] = &aOvflSpace[apDiv[i]-pParent->aData];
}
}
dropCell(pParent, i+nxDiv-pParent->nOverflow, szNew[i], &rc);
}
}
/* Make nMaxCells a multiple of 4 in order to preserve 8-byte
** alignment */
nMaxCells = (nMaxCells + 3)&~3;
/*
** Allocate space for memory structures
*/
szScratch =
nMaxCells*sizeof(u8*) /* b.apCell */
+ nMaxCells*sizeof(u16) /* b.szCell */
+ pBt->pageSize; /* aSpace1 */
/* EVIDENCE-OF: R-28375-38319 SQLite will never request a scratch buffer
** that is more than 6 times the database page size. */
assert( szScratch<=6*(int)pBt->pageSize );
b.apCell = sqlite3ScratchMalloc( szScratch );
if( b.apCell==0 ){
rc = SQLITE_NOMEM_BKPT;
goto balance_cleanup;
}
b.szCell = (u16*)&b.apCell[nMaxCells];
aSpace1 = (u8*)&b.szCell[nMaxCells];
assert( EIGHT_BYTE_ALIGNMENT(aSpace1) );
/*
** Load pointers to all cells on sibling pages and the divider cells
** into the local b.apCell[] array. Make copies of the divider cells
** into space obtained from aSpace1[]. The divider cells have already
** been removed from pParent.
**
** If the siblings are on leaf pages, then the child pointers of the
** divider cells are stripped from the cells before they are copied
** into aSpace1[]. In this way, all cells in b.apCell[] are without
** child pointers. If siblings are not leaves, then all cell in
** b.apCell[] include child pointers. Either way, all cells in b.apCell[]
** are alike.
**
** leafCorrection: 4 if pPage is a leaf. 0 if pPage is not a leaf.
** leafData: 1 if pPage holds key+data and pParent holds only keys.
*/
b.pRef = apOld[0];
leafCorrection = b.pRef->leaf*4;
leafData = b.pRef->intKeyLeaf;
for(i=0; i<nOld; i++){
MemPage *pOld = apOld[i];
int limit = pOld->nCell;
u8 *aData = pOld->aData;
u16 maskPage = pOld->maskPage;
u8 *piCell = aData + pOld->cellOffset;
u8 *piEnd;
/* Verify that all sibling pages are of the same "type" (table-leaf,
** table-interior, index-leaf, or index-interior).
*/
if( pOld->aData[0]!=apOld[0]->aData[0] ){
rc = SQLITE_CORRUPT_BKPT;
goto balance_cleanup;
}
/* Load b.apCell[] with pointers to all cells in pOld. If pOld
** constains overflow cells, include them in the b.apCell[] array
** in the correct spot.
**
** Note that when there are multiple overflow cells, it is always the
** case that they are sequential and adjacent. This invariant arises
** because multiple overflows can only occurs when inserting divider
** cells into a parent on a prior balance, and divider cells are always
** adjacent and are inserted in order. There is an assert() tagged
** with "NOTE 1" in the overflow cell insertion loop to prove this
** invariant.
**
** This must be done in advance. Once the balance starts, the cell
** offset section of the btree page will be overwritten and we will no
** long be able to find the cells if a pointer to each cell is not saved
** first.
*/
memset(&b.szCell[b.nCell], 0, sizeof(b.szCell[0])*(limit+pOld->nOverflow));
if( pOld->nOverflow>0 ){
limit = pOld->aiOvfl[0];
for(j=0; j<limit; j++){
b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
piCell += 2;
b.nCell++;
}
for(k=0; k<pOld->nOverflow; k++){
assert( k==0 || pOld->aiOvfl[k-1]+1==pOld->aiOvfl[k] );/* NOTE 1 */
b.apCell[b.nCell] = pOld->apOvfl[k];
b.nCell++;
}
}
piEnd = aData + pOld->cellOffset + 2*pOld->nCell;
while( piCell<piEnd ){
assert( b.nCell<nMaxCells );
b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
piCell += 2;
b.nCell++;
}
cntOld[i] = b.nCell;
if( i<nOld-1 && !leafData){
u16 sz = (u16)szNew[i];
u8 *pTemp;
assert( b.nCell<nMaxCells );
b.szCell[b.nCell] = sz;
pTemp = &aSpace1[iSpace1];
iSpace1 += sz;
assert( sz<=pBt->maxLocal+23 );
assert( iSpace1 <= (int)pBt->pageSize );
memcpy(pTemp, apDiv[i], sz);
b.apCell[b.nCell] = pTemp+leafCorrection;
assert( leafCorrection==0 || leafCorrection==4 );
b.szCell[b.nCell] = b.szCell[b.nCell] - leafCorrection;
if( !pOld->leaf ){
assert( leafCorrection==0 );
assert( pOld->hdrOffset==0 );
/* The right pointer of the child page pOld becomes the left
** pointer of the divider cell */
memcpy(b.apCell[b.nCell], &pOld->aData[8], 4);
}else{
assert( leafCorrection==4 );
while( b.szCell[b.nCell]<4 ){
/* Do not allow any cells smaller than 4 bytes. If a smaller cell
** does exist, pad it with 0x00 bytes. */
assert( b.szCell[b.nCell]==3 || CORRUPT_DB );
assert( b.apCell[b.nCell]==&aSpace1[iSpace1-3] || CORRUPT_DB );
aSpace1[iSpace1++] = 0x00;
b.szCell[b.nCell]++;
}
}
b.nCell++;
}
}
/*
** Figure out the number of pages needed to hold all b.nCell cells.
** Store this number in "k". Also compute szNew[] which is the total
** size of all cells on the i-th page and cntNew[] which is the index
** in b.apCell[] of the cell that divides page i from page i+1.
** cntNew[k] should equal b.nCell.
**
** Values computed by this block:
**
** k: The total number of sibling pages
** szNew[i]: Spaced used on the i-th sibling page.
** cntNew[i]: Index in b.apCell[] and b.szCell[] for the first cell to
** the right of the i-th sibling page.
** usableSpace: Number of bytes of space available on each sibling.
**
*/
usableSpace = pBt->usableSize - 12 + leafCorrection;
for(i=0; i<nOld; i++){
MemPage *p = apOld[i];
szNew[i] = usableSpace - p->nFree;
if( szNew[i]<0 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
for(j=0; j<p->nOverflow; j++){
szNew[i] += 2 + p->xCellSize(p, p->apOvfl[j]);
}
cntNew[i] = cntOld[i];
}
k = nOld;
for(i=0; i<k; i++){
int sz;
while( szNew[i]>usableSpace ){
if( i+1>=k ){
k = i+2;
if( k>NB+2 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
szNew[k-1] = 0;
cntNew[k-1] = b.nCell;
}
sz = 2 + cachedCellSize(&b, cntNew[i]-1);
szNew[i] -= sz;
if( !leafData ){
if( cntNew[i]<b.nCell ){
sz = 2 + cachedCellSize(&b, cntNew[i]);
}else{
sz = 0;
}
}
szNew[i+1] += sz;
cntNew[i]--;
}
while( cntNew[i]<b.nCell ){
sz = 2 + cachedCellSize(&b, cntNew[i]);
if( szNew[i]+sz>usableSpace ) break;
szNew[i] += sz;
cntNew[i]++;
if( !leafData ){
if( cntNew[i]<b.nCell ){
sz = 2 + cachedCellSize(&b, cntNew[i]);
}else{
sz = 0;
}
}
szNew[i+1] -= sz;
}
if( cntNew[i]>=b.nCell ){
k = i+1;
}else if( cntNew[i] <= (i>0 ? cntNew[i-1] : 0) ){
rc = SQLITE_CORRUPT_BKPT;
goto balance_cleanup;
}
}
/*
** The packing computed by the previous block is biased toward the siblings
** on the left side (siblings with smaller keys). The left siblings are
** always nearly full, while the right-most sibling might be nearly empty.
** The next block of code attempts to adjust the packing of siblings to
** get a better balance.
**
** This adjustment is more than an optimization. The packing above might
** be so out of balance as to be illegal. For example, the right-most
** sibling might be completely empty. This adjustment is not optional.
*/
for(i=k-1; i>0; i--){
int szRight = szNew[i]; /* Size of sibling on the right */
int szLeft = szNew[i-1]; /* Size of sibling on the left */
int r; /* Index of right-most cell in left sibling */
int d; /* Index of first cell to the left of right sibling */
r = cntNew[i-1] - 1;
d = r + 1 - leafData;
(void)cachedCellSize(&b, d);
do{
assert( d<nMaxCells );
assert( r<nMaxCells );
(void)cachedCellSize(&b, r);
if( szRight!=0
&& (bBulk || szRight+b.szCell[d]+2 > szLeft-(b.szCell[r]+(i==k-1?0:2)))){
break;
}
szRight += b.szCell[d] + 2;
szLeft -= b.szCell[r] + 2;
cntNew[i-1] = r;
r--;
d--;
}while( r>=0 );
szNew[i] = szRight;
szNew[i-1] = szLeft;
if( cntNew[i-1] <= (i>1 ? cntNew[i-2] : 0) ){
rc = SQLITE_CORRUPT_BKPT;
goto balance_cleanup;
}
}
/* Sanity check: For a non-corrupt database file one of the follwing
** must be true:
** (1) We found one or more cells (cntNew[0])>0), or
** (2) pPage is a virtual root page. A virtual root page is when
** the real root page is page 1 and we are the only child of
** that page.
*/
assert( cntNew[0]>0 || (pParent->pgno==1 && pParent->nCell==0) || CORRUPT_DB);
TRACE(("BALANCE: old: %d(nc=%d) %d(nc=%d) %d(nc=%d)\n",
apOld[0]->pgno, apOld[0]->nCell,
nOld>=2 ? apOld[1]->pgno : 0, nOld>=2 ? apOld[1]->nCell : 0,
nOld>=3 ? apOld[2]->pgno : 0, nOld>=3 ? apOld[2]->nCell : 0
));
/*
** Allocate k new pages. Reuse old pages where possible.
*/
pageFlags = apOld[0]->aData[0];
for(i=0; i<k; i++){
MemPage *pNew;
if( i<nOld ){
pNew = apNew[i] = apOld[i];
apOld[i] = 0;
rc = sqlite3PagerWrite(pNew->pDbPage);
nNew++;
if( rc ) goto balance_cleanup;
}else{
assert( i>0 );
rc = allocateBtreePage(pBt, &pNew, &pgno, (bBulk ? 1 : pgno), 0);
if( rc ) goto balance_cleanup;
zeroPage(pNew, pageFlags);
apNew[i] = pNew;
nNew++;
cntOld[i] = b.nCell;
/* Set the pointer-map entry for the new sibling page. */
if( ISAUTOVACUUM ){
ptrmapPut(pBt, pNew->pgno, PTRMAP_BTREE, pParent->pgno, &rc);
if( rc!=SQLITE_OK ){
goto balance_cleanup;
}
}
}
}
/*
** Reassign page numbers so that the new pages are in ascending order.
** This helps to keep entries in the disk file in order so that a scan
** of the table is closer to a linear scan through the file. That in turn
** helps the operating system to deliver pages from the disk more rapidly.
**
** An O(n^2) insertion sort algorithm is used, but since n is never more
** than (NB+2) (a small constant), that should not be a problem.
**
** When NB==3, this one optimization makes the database about 25% faster
** for large insertions and deletions.
*/
for(i=0; i<nNew; i++){
aPgOrder[i] = aPgno[i] = apNew[i]->pgno;
aPgFlags[i] = apNew[i]->pDbPage->flags;
for(j=0; j<i; j++){
if( aPgno[j]==aPgno[i] ){
/* This branch is taken if the set of sibling pages somehow contains
** duplicate entries. This can happen if the database is corrupt.
** It would be simpler to detect this as part of the loop below, but
** we do the detection here in order to avoid populating the pager
** cache with two separate objects associated with the same
** page number. */
assert( CORRUPT_DB );
rc = SQLITE_CORRUPT_BKPT;
goto balance_cleanup;
}
}
}
for(i=0; i<nNew; i++){
int iBest = 0; /* aPgno[] index of page number to use */
for(j=1; j<nNew; j++){
if( aPgOrder[j]<aPgOrder[iBest] ) iBest = j;
}
pgno = aPgOrder[iBest];
aPgOrder[iBest] = 0xffffffff;
if( iBest!=i ){
if( iBest>i ){
sqlite3PagerRekey(apNew[iBest]->pDbPage, pBt->nPage+iBest+1, 0);
}
sqlite3PagerRekey(apNew[i]->pDbPage, pgno, aPgFlags[iBest]);
apNew[i]->pgno = pgno;
}
}
TRACE(("BALANCE: new: %d(%d nc=%d) %d(%d nc=%d) %d(%d nc=%d) "
"%d(%d nc=%d) %d(%d nc=%d)\n",
apNew[0]->pgno, szNew[0], cntNew[0],
nNew>=2 ? apNew[1]->pgno : 0, nNew>=2 ? szNew[1] : 0,
nNew>=2 ? cntNew[1] - cntNew[0] - !leafData : 0,
nNew>=3 ? apNew[2]->pgno : 0, nNew>=3 ? szNew[2] : 0,
nNew>=3 ? cntNew[2] - cntNew[1] - !leafData : 0,
nNew>=4 ? apNew[3]->pgno : 0, nNew>=4 ? szNew[3] : 0,
nNew>=4 ? cntNew[3] - cntNew[2] - !leafData : 0,
nNew>=5 ? apNew[4]->pgno : 0, nNew>=5 ? szNew[4] : 0,
nNew>=5 ? cntNew[4] - cntNew[3] - !leafData : 0
));
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
put4byte(pRight, apNew[nNew-1]->pgno);
/* If the sibling pages are not leaves, ensure that the right-child pointer
** of the right-most new sibling page is set to the value that was
** originally in the same field of the right-most old sibling page. */
if( (pageFlags & PTF_LEAF)==0 && nOld!=nNew ){
MemPage *pOld = (nNew>nOld ? apNew : apOld)[nOld-1];
memcpy(&apNew[nNew-1]->aData[8], &pOld->aData[8], 4);
}
/* Make any required updates to pointer map entries associated with
** cells stored on sibling pages following the balance operation. Pointer
** map entries associated with divider cells are set by the insertCell()
** routine. The associated pointer map entries are:
**
** a) if the cell contains a reference to an overflow chain, the
** entry associated with the first page in the overflow chain, and
**
** b) if the sibling pages are not leaves, the child page associated
** with the cell.
**
** If the sibling pages are not leaves, then the pointer map entry
** associated with the right-child of each sibling may also need to be
** updated. This happens below, after the sibling pages have been
** populated, not here.
*/
if( ISAUTOVACUUM ){
MemPage *pNew = apNew[0];
u8 *aOld = pNew->aData;
int cntOldNext = pNew->nCell + pNew->nOverflow;
int usableSize = pBt->usableSize;
int iNew = 0;
int iOld = 0;
for(i=0; i<b.nCell; i++){
u8 *pCell = b.apCell[i];
if( i==cntOldNext ){
MemPage *pOld = (++iOld)<nNew ? apNew[iOld] : apOld[iOld];
cntOldNext += pOld->nCell + pOld->nOverflow + !leafData;
aOld = pOld->aData;
}
if( i==cntNew[iNew] ){
pNew = apNew[++iNew];
if( !leafData ) continue;
}
/* Cell pCell is destined for new sibling page pNew. Originally, it
** was either part of sibling page iOld (possibly an overflow cell),
** or else the divider cell to the left of sibling page iOld. So,
** if sibling page iOld had the same page number as pNew, and if
** pCell really was a part of sibling page iOld (not a divider or
** overflow cell), we can skip updating the pointer map entries. */
if( iOld>=nNew
|| pNew->pgno!=aPgno[iOld]
|| !SQLITE_WITHIN(pCell,aOld,&aOld[usableSize])
){
if( !leafCorrection ){
ptrmapPut(pBt, get4byte(pCell), PTRMAP_BTREE, pNew->pgno, &rc);
}
if( cachedCellSize(&b,i)>pNew->minLocal ){
ptrmapPutOvflPtr(pNew, pCell, &rc);
}
if( rc ) goto balance_cleanup;
}
}
}
/* Insert new divider cells into pParent. */
for(i=0; i<nNew-1; i++){
u8 *pCell;
u8 *pTemp;
int sz;
MemPage *pNew = apNew[i];
j = cntNew[i];
assert( j<nMaxCells );
assert( b.apCell[j]!=0 );
pCell = b.apCell[j];
sz = b.szCell[j] + leafCorrection;
pTemp = &aOvflSpace[iOvflSpace];
if( !pNew->leaf ){
memcpy(&pNew->aData[8], pCell, 4);
}else if( leafData ){
/* If the tree is a leaf-data tree, and the siblings are leaves,
** then there is no divider cell in b.apCell[]. Instead, the divider
** cell consists of the integer key for the right-most cell of
** the sibling-page assembled above only.
*/
CellInfo info;
j--;
pNew->xParseCell(pNew, b.apCell[j], &info);
pCell = pTemp;
sz = 4 + putVarint(&pCell[4], info.nKey);
pTemp = 0;
}else{
pCell -= 4;
/* Obscure case for non-leaf-data trees: If the cell at pCell was
** previously stored on a leaf node, and its reported size was 4
** bytes, then it may actually be smaller than this
** (see btreeParseCellPtr(), 4 bytes is the minimum size of
** any cell). But it is important to pass the correct size to
** insertCell(), so reparse the cell now.
**
** This can only happen for b-trees used to evaluate "IN (SELECT ...)"
** and WITHOUT ROWID tables with exactly one column which is the
** primary key.
*/
if( b.szCell[j]==4 ){
assert(leafCorrection==4);
sz = pParent->xCellSize(pParent, pCell);
}
}
iOvflSpace += sz;
assert( sz<=pBt->maxLocal+23 );
assert( iOvflSpace <= (int)pBt->pageSize );
insertCell(pParent, nxDiv+i, pCell, sz, pTemp, pNew->pgno, &rc);
if( rc!=SQLITE_OK ) goto balance_cleanup;
assert( sqlite3PagerIswriteable(pParent->pDbPage) );
}
/* Now update the actual sibling pages. The order in which they are updated
** is important, as this code needs to avoid disrupting any page from which
** cells may still to be read. In practice, this means:
**
** (1) If cells are moving left (from apNew[iPg] to apNew[iPg-1])
** then it is not safe to update page apNew[iPg] until after
** the left-hand sibling apNew[iPg-1] has been updated.
**
** (2) If cells are moving right (from apNew[iPg] to apNew[iPg+1])
** then it is not safe to update page apNew[iPg] until after
** the right-hand sibling apNew[iPg+1] has been updated.
**
** If neither of the above apply, the page is safe to update.
**
** The iPg value in the following loop starts at nNew-1 goes down
** to 0, then back up to nNew-1 again, thus making two passes over
** the pages. On the initial downward pass, only condition (1) above
** needs to be tested because (2) will always be true from the previous
** step. On the upward pass, both conditions are always true, so the
** upwards pass simply processes pages that were missed on the downward
** pass.
*/
for(i=1-nNew; i<nNew; i++){
int iPg = i<0 ? -i : i;
assert( iPg>=0 && iPg<nNew );
if( abDone[iPg] ) continue; /* Skip pages already processed */
if( i>=0 /* On the upwards pass, or... */
|| cntOld[iPg-1]>=cntNew[iPg-1] /* Condition (1) is true */
){
int iNew;
int iOld;
int nNewCell;
/* Verify condition (1): If cells are moving left, update iPg
** only after iPg-1 has already been updated. */
assert( iPg==0 || cntOld[iPg-1]>=cntNew[iPg-1] || abDone[iPg-1] );
/* Verify condition (2): If cells are moving right, update iPg
** only after iPg+1 has already been updated. */
assert( cntNew[iPg]>=cntOld[iPg] || abDone[iPg+1] );
if( iPg==0 ){
iNew = iOld = 0;
nNewCell = cntNew[0];
}else{
iOld = iPg<nOld ? (cntOld[iPg-1] + !leafData) : b.nCell;
iNew = cntNew[iPg-1] + !leafData;
nNewCell = cntNew[iPg] - iNew;
}
rc = editPage(apNew[iPg], iOld, iNew, nNewCell, &b);
if( rc ) goto balance_cleanup;
abDone[iPg]++;
apNew[iPg]->nFree = usableSpace-szNew[iPg];
assert( apNew[iPg]->nOverflow==0 );
assert( apNew[iPg]->nCell==nNewCell );
}
}
/* All pages have been processed exactly once */
assert( memcmp(abDone, "\01\01\01\01\01", nNew)==0 );
assert( nOld>0 );
assert( nNew>0 );
if( isRoot && pParent->nCell==0 && pParent->hdrOffset<=apNew[0]->nFree ){
/* The root page of the b-tree now contains no cells. The only sibling
** page is the right-child of the parent. Copy the contents of the
** child page into the parent, decreasing the overall height of the
** b-tree structure by one. This is described as the "balance-shallower"
** sub-algorithm in some documentation.
**
** If this is an auto-vacuum database, the call to copyNodeContent()
** sets all pointer-map entries corresponding to database image pages
** for which the pointer is stored within the content being copied.
**
** It is critical that the child page be defragmented before being
** copied into the parent, because if the parent is page 1 then it will
** by smaller than the child due to the database header, and so all the
** free space needs to be up front.
*/
assert( nNew==1 || CORRUPT_DB );
rc = defragmentPage(apNew[0]);
testcase( rc!=SQLITE_OK );
assert( apNew[0]->nFree ==
(get2byte(&apNew[0]->aData[5])-apNew[0]->cellOffset-apNew[0]->nCell*2)
|| rc!=SQLITE_OK
);
copyNodeContent(apNew[0], pParent, &rc);
freePage(apNew[0], &rc);
}else if( ISAUTOVACUUM && !leafCorrection ){
/* Fix the pointer map entries associated with the right-child of each
** sibling page. All other pointer map entries have already been taken
** care of. */
for(i=0; i<nNew; i++){
u32 key = get4byte(&apNew[i]->aData[8]);
ptrmapPut(pBt, key, PTRMAP_BTREE, apNew[i]->pgno, &rc);
}
}
assert( pParent->isInit );
TRACE(("BALANCE: finished: old=%d new=%d cells=%d\n",
nOld, nNew, b.nCell));
/* Free any old pages that were not reused as new pages.
*/
for(i=nNew; i<nOld; i++){
freePage(apOld[i], &rc);
}
#if 0
if( ISAUTOVACUUM && rc==SQLITE_OK && apNew[0]->isInit ){
/* The ptrmapCheckPages() contains assert() statements that verify that
** all pointer map pages are set correctly. This is helpful while
** debugging. This is usually disabled because a corrupt database may
** cause an assert() statement to fail. */
ptrmapCheckPages(apNew, nNew);
ptrmapCheckPages(&pParent, 1);
}
#endif
/*
** Cleanup before returning.
*/
balance_cleanup:
sqlite3ScratchFree(b.apCell);
for(i=0; i<nOld; i++){
releasePage(apOld[i]);
}
for(i=0; i<nNew; i++){
releasePage(apNew[i]);
}
return rc;
}
/*
** This function is called when the root page of a b-tree structure is
** overfull (has one or more overflow pages).
**
** A new child page is allocated and the contents of the current root
** page, including overflow cells, are copied into the child. The root
** page is then overwritten to make it an empty page with the right-child
** pointer pointing to the new page.
**
** Before returning, all pointer-map entries corresponding to pages
** that the new child-page now contains pointers to are updated. The
** entry corresponding to the new right-child pointer of the root
** page is also updated.
**
** If successful, *ppChild is set to contain a reference to the child
** page and SQLITE_OK is returned. In this case the caller is required
** to call releasePage() on *ppChild exactly once. If an error occurs,
** an error code is returned and *ppChild is set to 0.
*/
static int balance_deeper(MemPage *pRoot, MemPage **ppChild){
int rc; /* Return value from subprocedures */
MemPage *pChild = 0; /* Pointer to a new child page */
Pgno pgnoChild = 0; /* Page number of the new child page */
BtShared *pBt = pRoot->pBt; /* The BTree */
assert( pRoot->nOverflow>0 );
assert( sqlite3_mutex_held(pBt->mutex) );
/* Make pRoot, the root page of the b-tree, writable. Allocate a new
** page that will become the new right-child of pPage. Copy the contents
** of the node stored on pRoot into the new child page.
*/
rc = sqlite3PagerWrite(pRoot->pDbPage);
if( rc==SQLITE_OK ){
rc = allocateBtreePage(pBt,&pChild,&pgnoChild,pRoot->pgno,0);
copyNodeContent(pRoot, pChild, &rc);
if( ISAUTOVACUUM ){
ptrmapPut(pBt, pgnoChild, PTRMAP_BTREE, pRoot->pgno, &rc);
}
}
if( rc ){
*ppChild = 0;
releasePage(pChild);
return rc;
}
assert( sqlite3PagerIswriteable(pChild->pDbPage) );
assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
assert( pChild->nCell==pRoot->nCell );
TRACE(("BALANCE: copy root %d into %d\n", pRoot->pgno, pChild->pgno));
/* Copy the overflow cells from pRoot to pChild */
memcpy(pChild->aiOvfl, pRoot->aiOvfl,
pRoot->nOverflow*sizeof(pRoot->aiOvfl[0]));
memcpy(pChild->apOvfl, pRoot->apOvfl,
pRoot->nOverflow*sizeof(pRoot->apOvfl[0]));
pChild->nOverflow = pRoot->nOverflow;
/* Zero the contents of pRoot. Then install pChild as the right-child. */
zeroPage(pRoot, pChild->aData[0] & ~PTF_LEAF);
put4byte(&pRoot->aData[pRoot->hdrOffset+8], pgnoChild);
*ppChild = pChild;
return SQLITE_OK;
}
/*
** The page that pCur currently points to has just been modified in
** some way. This function figures out if this modification means the
** tree needs to be balanced, and if so calls the appropriate balancing
** routine. Balancing routines are:
**
** balance_quick()
** balance_deeper()
** balance_nonroot()
*/
static int balance(BtCursor *pCur){
int rc = SQLITE_OK;
const int nMin = pCur->pBt->usableSize * 2 / 3;
u8 aBalanceQuickSpace[13];
u8 *pFree = 0;
VVA_ONLY( int balance_quick_called = 0 );
VVA_ONLY( int balance_deeper_called = 0 );
do {
int iPage = pCur->iPage;
MemPage *pPage = pCur->apPage[iPage];
if( iPage==0 ){
if( pPage->nOverflow ){
/* The root page of the b-tree is overfull. In this case call the
** balance_deeper() function to create a new child for the root-page
** and copy the current contents of the root-page to it. The
** next iteration of the do-loop will balance the child page.
*/
assert( balance_deeper_called==0 );
VVA_ONLY( balance_deeper_called++ );
rc = balance_deeper(pPage, &pCur->apPage[1]);
if( rc==SQLITE_OK ){
pCur->iPage = 1;
pCur->aiIdx[0] = 0;
pCur->aiIdx[1] = 0;
assert( pCur->apPage[1]->nOverflow );
}
}else{
break;
}
}else if( pPage->nOverflow==0 && pPage->nFree<=nMin ){
break;
}else{
MemPage * const pParent = pCur->apPage[iPage-1];
int const iIdx = pCur->aiIdx[iPage-1];
rc = sqlite3PagerWrite(pParent->pDbPage);
if( rc==SQLITE_OK ){
#ifndef SQLITE_OMIT_QUICKBALANCE
if( pPage->intKeyLeaf
&& pPage->nOverflow==1
&& pPage->aiOvfl[0]==pPage->nCell
&& pParent->pgno!=1
&& pParent->nCell==iIdx
){
/* Call balance_quick() to create a new sibling of pPage on which
** to store the overflow cell. balance_quick() inserts a new cell
** into pParent, which may cause pParent overflow. If this
** happens, the next iteration of the do-loop will balance pParent
** use either balance_nonroot() or balance_deeper(). Until this
** happens, the overflow cell is stored in the aBalanceQuickSpace[]
** buffer.
**
** The purpose of the following assert() is to check that only a
** single call to balance_quick() is made for each call to this
** function. If this were not verified, a subtle bug involving reuse
** of the aBalanceQuickSpace[] might sneak in.
*/
assert( balance_quick_called==0 );
VVA_ONLY( balance_quick_called++ );
rc = balance_quick(pParent, pPage, aBalanceQuickSpace);
}else
#endif
{
/* In this case, call balance_nonroot() to redistribute cells
** between pPage and up to 2 of its sibling pages. This involves
** modifying the contents of pParent, which may cause pParent to
** become overfull or underfull. The next iteration of the do-loop
** will balance the parent page to correct this.
**
** If the parent page becomes overfull, the overflow cell or cells
** are stored in the pSpace buffer allocated immediately below.
** A subsequent iteration of the do-loop will deal with this by
** calling balance_nonroot() (balance_deeper() may be called first,
** but it doesn't deal with overflow cells - just moves them to a
** different page). Once this subsequent call to balance_nonroot()
** has completed, it is safe to release the pSpace buffer used by
** the previous call, as the overflow cell data will have been
** copied either into the body of a database page or into the new
** pSpace buffer passed to the latter call to balance_nonroot().
*/
u8 *pSpace = sqlite3PageMalloc(pCur->pBt->pageSize);
rc = balance_nonroot(pParent, iIdx, pSpace, iPage==1,
pCur->hints&BTREE_BULKLOAD);
if( pFree ){
/* If pFree is not NULL, it points to the pSpace buffer used
** by a previous call to balance_nonroot(). Its contents are
** now stored either on real database pages or within the
** new pSpace buffer, so it may be safely freed here. */
sqlite3PageFree(pFree);
}
/* The pSpace buffer will be freed after the next call to
** balance_nonroot(), or just before this function returns, whichever
** comes first. */
pFree = pSpace;
}
}
pPage->nOverflow = 0;
/* The next iteration of the do-loop balances the parent page. */
releasePage(pPage);
pCur->iPage--;
assert( pCur->iPage>=0 );
}
}while( rc==SQLITE_OK );
if( pFree ){
sqlite3PageFree(pFree);
}
return rc;
}
/*
** Insert a new record into the BTree. The content of the new record
** is described by the pX object. The pCur cursor is used only to
** define what table the record should be inserted into, and is left
** pointing at a random location.
**
** For a table btree (used for rowid tables), only the pX.nKey value of
** the key is used. The pX.pKey value must be NULL. The pX.nKey is the
** rowid or INTEGER PRIMARY KEY of the row. The pX.nData,pData,nZero fields
** hold the content of the row.
**
** For an index btree (used for indexes and WITHOUT ROWID tables), the
** key is an arbitrary byte sequence stored in pX.pKey,nKey. The
** pX.pData,nData,nZero fields must be zero.
**
** If the seekResult parameter is non-zero, then a successful call to
** MovetoUnpacked() to seek cursor pCur to (pKey, nKey) has already
** been performed. seekResult is the search result returned (a negative
** number if pCur points at an entry that is smaller than (pKey, nKey), or
** a positive value if pCur points at an entry that is larger than
** (pKey, nKey)).
**
** If the seekResult parameter is non-zero, then the caller guarantees that
** cursor pCur is pointing at the existing copy of a row that is to be
** overwritten. If the seekResult parameter is 0, then cursor pCur may
** point to any entry or to no entry at all and so this function has to seek
** the cursor before the new key can be inserted.
*/
int sqlite3BtreeInsert(
BtCursor *pCur, /* Insert data into the table of this cursor */
const BtreePayload *pX, /* Content of the row to be inserted */
int appendBias, /* True if this is likely an append */
int seekResult /* Result of prior MovetoUnpacked() call */
){
int rc;
int loc = seekResult; /* -1: before desired location +1: after */
int szNew = 0;
int idx;
MemPage *pPage;
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
unsigned char *oldCell;
unsigned char *newCell = 0;
if( pCur->eState==CURSOR_FAULT ){
assert( pCur->skipNext!=SQLITE_OK );
return pCur->skipNext;
}
assert( cursorOwnsBtShared(pCur) );
assert( (pCur->curFlags & BTCF_WriteFlag)!=0
&& pBt->inTransaction==TRANS_WRITE
&& (pBt->btsFlags & BTS_READ_ONLY)==0 );
assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
/* Assert that the caller has been consistent. If this cursor was opened
** expecting an index b-tree, then the caller should be inserting blob
** keys with no associated data. If the cursor was opened expecting an
** intkey table, the caller should be inserting integer keys with a
** blob of associated data. */
assert( (pX->pKey==0)==(pCur->pKeyInfo==0) );
/* Save the positions of any other cursors open on this table.
**
** In some cases, the call to btreeMoveto() below is a no-op. For
** example, when inserting data into a table with auto-generated integer
** keys, the VDBE layer invokes sqlite3BtreeLast() to figure out the
** integer key to use. It then calls this function to actually insert the
** data into the intkey B-Tree. In this case btreeMoveto() recognizes
** that the cursor is already where it needs to be and returns without
** doing any work. To avoid thwarting these optimizations, it is important
** not to clear the cursor here.
*/
if( pCur->curFlags & BTCF_Multiple ){
rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
if( rc ) return rc;
}
if( pCur->pKeyInfo==0 ){
assert( pX->pKey==0 );
/* If this is an insert into a table b-tree, invalidate any incrblob
** cursors open on the row being replaced */
invalidateIncrblobCursors(p, pX->nKey, 0);
/* If the cursor is currently on the last row and we are appending a
** new row onto the end, set the "loc" to avoid an unnecessary
** btreeMoveto() call */
if( (pCur->curFlags&BTCF_ValidNKey)!=0 && pX->nKey>0
&& pCur->info.nKey==pX->nKey-1 ){
loc = -1;
}else if( loc==0 ){
rc = sqlite3BtreeMovetoUnpacked(pCur, 0, pX->nKey, appendBias, &loc);
if( rc ) return rc;
}
}else if( loc==0 ){
rc = btreeMoveto(pCur, pX->pKey, pX->nKey, appendBias, &loc);
if( rc ) return rc;
}
assert( pCur->eState==CURSOR_VALID || (pCur->eState==CURSOR_INVALID && loc) );
pPage = pCur->apPage[pCur->iPage];
assert( pPage->intKey || pX->nKey>=0 );
assert( pPage->leaf || !pPage->intKey );
TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
pCur->pgnoRoot, pX->nKey, pX->nData, pPage->pgno,
loc==0 ? "overwrite" : "new entry"));
assert( pPage->isInit );
newCell = pBt->pTmpSpace;
assert( newCell!=0 );
rc = fillInCell(pPage, newCell, pX, &szNew);
if( rc ) goto end_insert;
assert( szNew==pPage->xCellSize(pPage, newCell) );
assert( szNew <= MX_CELL_SIZE(pBt) );
idx = pCur->aiIdx[pCur->iPage];
if( loc==0 ){
u16 szOld;
assert( idx<pPage->nCell );
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ){
goto end_insert;
}
oldCell = findCell(pPage, idx);
if( !pPage->leaf ){
memcpy(newCell, oldCell, 4);
}
rc = clearCell(pPage, oldCell, &szOld);
dropCell(pPage, idx, szOld, &rc);
if( rc ) goto end_insert;
}else if( loc<0 && pPage->nCell>0 ){
assert( pPage->leaf );
idx = ++pCur->aiIdx[pCur->iPage];
}else{
assert( pPage->leaf );
}
insertCell(pPage, idx, newCell, szNew, 0, 0, &rc);
assert( pPage->nOverflow==0 || rc==SQLITE_OK );
assert( rc!=SQLITE_OK || pPage->nCell>0 || pPage->nOverflow>0 );
/* If no error has occurred and pPage has an overflow cell, call balance()
** to redistribute the cells within the tree. Since balance() may move
** the cursor, zero the BtCursor.info.nSize and BTCF_ValidNKey
** variables.
**
** Previous versions of SQLite called moveToRoot() to move the cursor
** back to the root page as balance() used to invalidate the contents
** of BtCursor.apPage[] and BtCursor.aiIdx[]. Instead of doing that,
** set the cursor state to "invalid". This makes common insert operations
** slightly faster.
**
** There is a subtle but important optimization here too. When inserting
** multiple records into an intkey b-tree using a single cursor (as can
** happen while processing an "INSERT INTO ... SELECT" statement), it
** is advantageous to leave the cursor pointing to the last entry in
** the b-tree if possible. If the cursor is left pointing to the last
** entry in the table, and the next row inserted has an integer key
** larger than the largest existing key, it is possible to insert the
** row without seeking the cursor. This can be a big performance boost.
*/
pCur->info.nSize = 0;
if( pPage->nOverflow ){
assert( rc==SQLITE_OK );
pCur->curFlags &= ~(BTCF_ValidNKey);
rc = balance(pCur);
/* Must make sure nOverflow is reset to zero even if the balance()
** fails. Internal data structure corruption will result otherwise.
** Also, set the cursor state to invalid. This stops saveCursorPosition()
** from trying to save the current position of the cursor. */
pCur->apPage[pCur->iPage]->nOverflow = 0;
pCur->eState = CURSOR_INVALID;
}
assert( pCur->apPage[pCur->iPage]->nOverflow==0 );
end_insert:
return rc;
}
/*
** Delete the entry that the cursor is pointing to.
**
** If the BTREE_SAVEPOSITION bit of the flags parameter is zero, then
** the cursor is left pointing at an arbitrary location after the delete.
** But if that bit is set, then the cursor is left in a state such that
** the next call to BtreeNext() or BtreePrev() moves it to the same row
** as it would have been on if the call to BtreeDelete() had been omitted.
**
** The BTREE_AUXDELETE bit of flags indicates that is one of several deletes
** associated with a single table entry and its indexes. Only one of those
** deletes is considered the "primary" delete. The primary delete occurs
** on a cursor that is not a BTREE_FORDELETE cursor. All but one delete
** operation on non-FORDELETE cursors is tagged with the AUXDELETE flag.
** The BTREE_AUXDELETE bit is a hint that is not used by this implementation,
** but which might be used by alternative storage engines.
*/
int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
int rc; /* Return code */
MemPage *pPage; /* Page to delete cell from */
unsigned char *pCell; /* Pointer to cell to delete */
int iCellIdx; /* Index of cell to delete */
int iCellDepth; /* Depth of node containing pCell */
u16 szCell; /* Size of the cell being deleted */
int bSkipnext = 0; /* Leaf cursor in SKIPNEXT state */
u8 bPreserve = flags & BTREE_SAVEPOSITION; /* Keep cursor valid */
assert( cursorOwnsBtShared(pCur) );
assert( pBt->inTransaction==TRANS_WRITE );
assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
assert( pCur->curFlags & BTCF_WriteFlag );
assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
assert( !hasReadConflicts(p, pCur->pgnoRoot) );
assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
assert( pCur->eState==CURSOR_VALID );
assert( (flags & ~(BTREE_SAVEPOSITION | BTREE_AUXDELETE))==0 );
iCellDepth = pCur->iPage;
iCellIdx = pCur->aiIdx[iCellDepth];
pPage = pCur->apPage[iCellDepth];
pCell = findCell(pPage, iCellIdx);
/* If the bPreserve flag is set to true, then the cursor position must
** be preserved following this delete operation. If the current delete
** will cause a b-tree rebalance, then this is done by saving the cursor
** key and leaving the cursor in CURSOR_REQUIRESEEK state before
** returning.
**
** Or, if the current delete will not cause a rebalance, then the cursor
** will be left in CURSOR_SKIPNEXT state pointing to the entry immediately
** before or after the deleted entry. In this case set bSkipnext to true. */
if( bPreserve ){
if( !pPage->leaf
|| (pPage->nFree+cellSizePtr(pPage,pCell)+2)>(int)(pBt->usableSize*2/3)
){
/* A b-tree rebalance will be required after deleting this entry.
** Save the cursor key. */
rc = saveCursorKey(pCur);
if( rc ) return rc;
}else{
bSkipnext = 1;
}
}
/* If the page containing the entry to delete is not a leaf page, move
** the cursor to the largest entry in the tree that is smaller than
** the entry being deleted. This cell will replace the cell being deleted
** from the internal node. The 'previous' entry is used for this instead
** of the 'next' entry, as the previous entry is always a part of the
** sub-tree headed by the child page of the cell being deleted. This makes
** balancing the tree following the delete operation easier. */
if( !pPage->leaf ){
int notUsed = 0;
rc = sqlite3BtreePrevious(pCur, ¬Used);
if( rc ) return rc;
}
/* Save the positions of any other cursors open on this table before
** making any modifications. */
if( pCur->curFlags & BTCF_Multiple ){
rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
if( rc ) return rc;
}
/* If this is a delete operation to remove a row from a table b-tree,
** invalidate any incrblob cursors open on the row being deleted. */
if( pCur->pKeyInfo==0 ){
invalidateIncrblobCursors(p, pCur->info.nKey, 0);
}
/* Make the page containing the entry to be deleted writable. Then free any
** overflow pages associated with the entry and finally remove the cell
** itself from within the page. */
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc ) return rc;
rc = clearCell(pPage, pCell, &szCell);
dropCell(pPage, iCellIdx, szCell, &rc);
if( rc ) return rc;
/* If the cell deleted was not located on a leaf page, then the cursor
** is currently pointing to the largest entry in the sub-tree headed
** by the child-page of the cell that was just deleted from an internal
** node. The cell from the leaf node needs to be moved to the internal
** node to replace the deleted cell. */
if( !pPage->leaf ){
MemPage *pLeaf = pCur->apPage[pCur->iPage];
int nCell;
Pgno n = pCur->apPage[iCellDepth+1]->pgno;
unsigned char *pTmp;
pCell = findCell(pLeaf, pLeaf->nCell-1);
if( pCell<&pLeaf->aData[4] ) return SQLITE_CORRUPT_BKPT;
nCell = pLeaf->xCellSize(pLeaf, pCell);
assert( MX_CELL_SIZE(pBt) >= nCell );
pTmp = pBt->pTmpSpace;
assert( pTmp!=0 );
rc = sqlite3PagerWrite(pLeaf->pDbPage);
if( rc==SQLITE_OK ){
insertCell(pPage, iCellIdx, pCell-4, nCell+4, pTmp, n, &rc);
}
dropCell(pLeaf, pLeaf->nCell-1, nCell, &rc);
if( rc ) return rc;
}
/* Balance the tree. If the entry deleted was located on a leaf page,
** then the cursor still points to that page. In this case the first
** call to balance() repairs the tree, and the if(...) condition is
** never true.
**
** Otherwise, if the entry deleted was on an internal node page, then
** pCur is pointing to the leaf page from which a cell was removed to
** replace the cell deleted from the internal node. This is slightly
** tricky as the leaf node may be underfull, and the internal node may
** be either under or overfull. In this case run the balancing algorithm
** on the leaf node first. If the balance proceeds far enough up the
** tree that we can be sure that any problem in the internal node has
** been corrected, so be it. Otherwise, after balancing the leaf node,
** walk the cursor up the tree to the internal node and balance it as
** well. */
rc = balance(pCur);
if( rc==SQLITE_OK && pCur->iPage>iCellDepth ){
while( pCur->iPage>iCellDepth ){
releasePage(pCur->apPage[pCur->iPage--]);
}
rc = balance(pCur);
}
if( rc==SQLITE_OK ){
if( bSkipnext ){
assert( bPreserve && (pCur->iPage==iCellDepth || CORRUPT_DB) );
assert( pPage==pCur->apPage[pCur->iPage] || CORRUPT_DB );
assert( (pPage->nCell>0 || CORRUPT_DB) && iCellIdx<=pPage->nCell );
pCur->eState = CURSOR_SKIPNEXT;
if( iCellIdx>=pPage->nCell ){
pCur->skipNext = -1;
pCur->aiIdx[iCellDepth] = pPage->nCell-1;
}else{
pCur->skipNext = 1;
}
}else{
rc = moveToRoot(pCur);
if( bPreserve ){
pCur->eState = CURSOR_REQUIRESEEK;
}
}
}
return rc;
}
/*
** Create a new BTree table. Write into *piTable the page
** number for the root page of the new table.
**
** The type of type is determined by the flags parameter. Only the
** following values of flags are currently in use. Other values for
** flags might not work:
**
** BTREE_INTKEY|BTREE_LEAFDATA Used for SQL tables with rowid keys
** BTREE_ZERODATA Used for SQL indices
*/
static int btreeCreateTable(Btree *p, int *piTable, int createTabFlags){
BtShared *pBt = p->pBt;
MemPage *pRoot;
Pgno pgnoRoot;
int rc;
int ptfFlags; /* Page-type flage for the root page of new table */
assert( sqlite3BtreeHoldsMutex(p) );
assert( pBt->inTransaction==TRANS_WRITE );
assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
#ifdef SQLITE_OMIT_AUTOVACUUM
rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
if( rc ){
return rc;
}
#else
if( pBt->autoVacuum ){
Pgno pgnoMove; /* Move a page here to make room for the root-page */
MemPage *pPageMove; /* The page to move to. */
/* Creating a new table may probably require moving an existing database
** to make room for the new tables root page. In case this page turns
** out to be an overflow page, delete all overflow page-map caches
** held by open cursors.
*/
invalidateAllOverflowCache(pBt);
/* Read the value of meta[3] from the database to determine where the
** root page of the new table should go. meta[3] is the largest root-page
** created so far, so the new root-page is (meta[3]+1).
*/
sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &pgnoRoot);
pgnoRoot++;
/* The new root-page may not be allocated on a pointer-map page, or the
** PENDING_BYTE page.
*/
while( pgnoRoot==PTRMAP_PAGENO(pBt, pgnoRoot) ||
pgnoRoot==PENDING_BYTE_PAGE(pBt) ){
pgnoRoot++;
}
assert( pgnoRoot>=3 || CORRUPT_DB );
testcase( pgnoRoot<3 );
/* Allocate a page. The page that currently resides at pgnoRoot will
** be moved to the allocated page (unless the allocated page happens
** to reside at pgnoRoot).
*/
rc = allocateBtreePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, BTALLOC_EXACT);
if( rc!=SQLITE_OK ){
return rc;
}
if( pgnoMove!=pgnoRoot ){
/* pgnoRoot is the page that will be used for the root-page of
** the new table (assuming an error did not occur). But we were
** allocated pgnoMove. If required (i.e. if it was not allocated
** by extending the file), the current page at position pgnoMove
** is already journaled.
*/
u8 eType = 0;
Pgno iPtrPage = 0;
/* Save the positions of any open cursors. This is required in
** case they are holding a reference to an xFetch reference
** corresponding to page pgnoRoot. */
rc = saveAllCursors(pBt, 0, 0);
releasePage(pPageMove);
if( rc!=SQLITE_OK ){
return rc;
}
/* Move the page currently at pgnoRoot to pgnoMove. */
rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = ptrmapGet(pBt, pgnoRoot, &eType, &iPtrPage);
if( eType==PTRMAP_ROOTPAGE || eType==PTRMAP_FREEPAGE ){
rc = SQLITE_CORRUPT_BKPT;
}
if( rc!=SQLITE_OK ){
releasePage(pRoot);
return rc;
}
assert( eType!=PTRMAP_ROOTPAGE );
assert( eType!=PTRMAP_FREEPAGE );
rc = relocatePage(pBt, pRoot, eType, iPtrPage, pgnoMove, 0);
releasePage(pRoot);
/* Obtain the page at pgnoRoot */
if( rc!=SQLITE_OK ){
return rc;
}
rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pRoot->pDbPage);
if( rc!=SQLITE_OK ){
releasePage(pRoot);
return rc;
}
}else{
pRoot = pPageMove;
}
/* Update the pointer-map and meta-data with the new root-page number. */
ptrmapPut(pBt, pgnoRoot, PTRMAP_ROOTPAGE, 0, &rc);
if( rc ){
releasePage(pRoot);
return rc;
}
/* When the new root page was allocated, page 1 was made writable in
** order either to increase the database filesize, or to decrement the
** freelist count. Hence, the sqlite3BtreeUpdateMeta() call cannot fail.
*/
assert( sqlite3PagerIswriteable(pBt->pPage1->pDbPage) );
rc = sqlite3BtreeUpdateMeta(p, 4, pgnoRoot);
if( NEVER(rc) ){
releasePage(pRoot);
return rc;
}
}else{
rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
if( rc ) return rc;
}
#endif
assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
if( createTabFlags & BTREE_INTKEY ){
ptfFlags = PTF_INTKEY | PTF_LEAFDATA | PTF_LEAF;
}else{
ptfFlags = PTF_ZERODATA | PTF_LEAF;
}
zeroPage(pRoot, ptfFlags);
sqlite3PagerUnref(pRoot->pDbPage);
assert( (pBt->openFlags & BTREE_SINGLE)==0 || pgnoRoot==2 );
*piTable = (int)pgnoRoot;
return SQLITE_OK;
}
int sqlite3BtreeCreateTable(Btree *p, int *piTable, int flags){
int rc;
sqlite3BtreeEnter(p);
rc = btreeCreateTable(p, piTable, flags);
sqlite3BtreeLeave(p);
return rc;
}
/*
** Erase the given database page and all its children. Return
** the page to the freelist.
*/
static int clearDatabasePage(
BtShared *pBt, /* The BTree that contains the table */
Pgno pgno, /* Page number to clear */
int freePageFlag, /* Deallocate page if true */
int *pnChange /* Add number of Cells freed to this counter */
){
MemPage *pPage;
int rc;
unsigned char *pCell;
int i;
int hdr;
u16 szCell;
assert( sqlite3_mutex_held(pBt->mutex) );
if( pgno>btreePagecount(pBt) ){
return SQLITE_CORRUPT_BKPT;
}
rc = getAndInitPage(pBt, pgno, &pPage, 0, 0);
if( rc ) return rc;
if( pPage->bBusy ){
rc = SQLITE_CORRUPT_BKPT;
goto cleardatabasepage_out;
}
pPage->bBusy = 1;
hdr = pPage->hdrOffset;
for(i=0; i<pPage->nCell; i++){
pCell = findCell(pPage, i);
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(pCell), 1, pnChange);
if( rc ) goto cleardatabasepage_out;
}
rc = clearCell(pPage, pCell, &szCell);
if( rc ) goto cleardatabasepage_out;
}
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(&pPage->aData[hdr+8]), 1, pnChange);
if( rc ) goto cleardatabasepage_out;
}else if( pnChange ){
assert( pPage->intKey || CORRUPT_DB );
testcase( !pPage->intKey );
*pnChange += pPage->nCell;
}
if( freePageFlag ){
freePage(pPage, &rc);
}else if( (rc = sqlite3PagerWrite(pPage->pDbPage))==0 ){
zeroPage(pPage, pPage->aData[hdr] | PTF_LEAF);
}
cleardatabasepage_out:
pPage->bBusy = 0;
releasePage(pPage);
return rc;
}
/*
** Delete all information from a single table in the database. iTable is
** the page number of the root of the table. After this routine returns,
** the root page is empty, but still exists.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** read cursors on the table. Open write cursors are moved to the
** root of the table.
**
** If pnChange is not NULL, then table iTable must be an intkey table. The
** integer value pointed to by pnChange is incremented by the number of
** entries in the table.
*/
int sqlite3BtreeClearTable(Btree *p, int iTable, int *pnChange){
int rc;
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
assert( p->inTrans==TRANS_WRITE );
rc = saveAllCursors(pBt, (Pgno)iTable, 0);
if( SQLITE_OK==rc ){
/* Invalidate all incrblob cursors open on table iTable (assuming iTable
** is the root of a table b-tree - if it is not, the following call is
** a no-op). */
invalidateIncrblobCursors(p, 0, 1);
rc = clearDatabasePage(pBt, (Pgno)iTable, 0, pnChange);
}
sqlite3BtreeLeave(p);
return rc;
}
/*
** Delete all information from the single table that pCur is open on.
**
** This routine only work for pCur on an ephemeral table.
*/
int sqlite3BtreeClearTableOfCursor(BtCursor *pCur){
return sqlite3BtreeClearTable(pCur->pBtree, pCur->pgnoRoot, 0);
}
/*
** Erase all information in a table and add the root of the table to
** the freelist. Except, the root of the principle table (the one on
** page 1) is never added to the freelist.
**
** This routine will fail with SQLITE_LOCKED if there are any open
** cursors on the table.
**
** If AUTOVACUUM is enabled and the page at iTable is not the last
** root page in the database file, then the last root page
** in the database file is moved into the slot formerly occupied by
** iTable and that last slot formerly occupied by the last root page
** is added to the freelist instead of iTable. In this say, all
** root pages are kept at the beginning of the database file, which
** is necessary for AUTOVACUUM to work right. *piMoved is set to the
** page number that used to be the last root page in the file before
** the move. If no page gets moved, *piMoved is set to 0.
** The last root page is recorded in meta[3] and the value of
** meta[3] is updated by this procedure.
*/
static int btreeDropTable(Btree *p, Pgno iTable, int *piMoved){
int rc;
MemPage *pPage = 0;
BtShared *pBt = p->pBt;
assert( sqlite3BtreeHoldsMutex(p) );
assert( p->inTrans==TRANS_WRITE );
/* It is illegal to drop a table if any cursors are open on the
** database. This is because in auto-vacuum mode the backend may
** need to move another root-page to fill a gap left by the deleted
** root page. If an open cursor was using this page a problem would
** occur.
**
** This error is caught long before control reaches this point.
*/
if( NEVER(pBt->pCursor) ){
sqlite3ConnectionBlocked(p->db, pBt->pCursor->pBtree->db);
return SQLITE_LOCKED_SHAREDCACHE;
}
/*
** It is illegal to drop the sqlite_master table on page 1. But again,
** this error is caught long before reaching this point.
*/
if( NEVER(iTable<2) ){
return SQLITE_CORRUPT_BKPT;
}
rc = btreeGetPage(pBt, (Pgno)iTable, &pPage, 0);
if( rc ) return rc;
rc = sqlite3BtreeClearTable(p, iTable, 0);
if( rc ){
releasePage(pPage);
return rc;
}
*piMoved = 0;
#ifdef SQLITE_OMIT_AUTOVACUUM
freePage(pPage, &rc);
releasePage(pPage);
#else
if( pBt->autoVacuum ){
Pgno maxRootPgno;
sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &maxRootPgno);
if( iTable==maxRootPgno ){
/* If the table being dropped is the table with the largest root-page
** number in the database, put the root page on the free list.
*/
freePage(pPage, &rc);
releasePage(pPage);
if( rc!=SQLITE_OK ){
return rc;
}
}else{
/* The table being dropped does not have the largest root-page
** number in the database. So move the page that does into the
** gap left by the deleted root-page.
*/
MemPage *pMove;
releasePage(pPage);
rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
if( rc!=SQLITE_OK ){
return rc;
}
rc = relocatePage(pBt, pMove, PTRMAP_ROOTPAGE, 0, iTable, 0);
releasePage(pMove);
if( rc!=SQLITE_OK ){
return rc;
}
pMove = 0;
rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
freePage(pMove, &rc);
releasePage(pMove);
if( rc!=SQLITE_OK ){
return rc;
}
*piMoved = maxRootPgno;
}
/* Set the new 'max-root-page' value in the database header. This
** is the old value less one, less one more if that happens to
** be a root-page number, less one again if that is the
** PENDING_BYTE_PAGE.
*/
maxRootPgno--;
while( maxRootPgno==PENDING_BYTE_PAGE(pBt)
|| PTRMAP_ISPAGE(pBt, maxRootPgno) ){
maxRootPgno--;
}
assert( maxRootPgno!=PENDING_BYTE_PAGE(pBt) );
rc = sqlite3BtreeUpdateMeta(p, 4, maxRootPgno);
}else{
freePage(pPage, &rc);
releasePage(pPage);
}
#endif
return rc;
}
int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
int rc;
sqlite3BtreeEnter(p);
rc = btreeDropTable(p, iTable, piMoved);
sqlite3BtreeLeave(p);
return rc;
}
/*
** This function may only be called if the b-tree connection already
** has a read or write transaction open on the database.
**
** Read the meta-information out of a database file. Meta[0]
** is the number of free pages currently in the database. Meta[1]
** through meta[15] are available for use by higher layers. Meta[0]
** is read-only, the others are read/write.
**
** The schema layer numbers meta values differently. At the schema
** layer (and the SetCookie and ReadCookie opcodes) the number of
** free pages is not visible. So Cookie[0] is the same as Meta[1].
**
** This routine treats Meta[BTREE_DATA_VERSION] as a special case. Instead
** of reading the value out of the header, it instead loads the "DataVersion"
** from the pager. The BTREE_DATA_VERSION value is not actually stored in the
** database file. It is a number computed by the pager. But its access
** pattern is the same as header meta values, and so it is convenient to
** read it from this routine.
*/
void sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
assert( p->inTrans>TRANS_NONE );
assert( SQLITE_OK==querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK) );
assert( pBt->pPage1 );
assert( idx>=0 && idx<=15 );
if( idx==BTREE_DATA_VERSION ){
*pMeta = sqlite3PagerDataVersion(pBt->pPager) + p->iDataVersion;
}else{
*pMeta = get4byte(&pBt->pPage1->aData[36 + idx*4]);
}
/* If auto-vacuum is disabled in this build and this is an auto-vacuum
** database, mark the database as read-only. */
#ifdef SQLITE_OMIT_AUTOVACUUM
if( idx==BTREE_LARGEST_ROOT_PAGE && *pMeta>0 ){
pBt->btsFlags |= BTS_READ_ONLY;
}
#endif
sqlite3BtreeLeave(p);
}
/*
** Write meta-information back into the database. Meta[0] is
** read-only and may not be written.
*/
int sqlite3BtreeUpdateMeta(Btree *p, int idx, u32 iMeta){
BtShared *pBt = p->pBt;
unsigned char *pP1;
int rc;
assert( idx>=1 && idx<=15 );
sqlite3BtreeEnter(p);
assert( p->inTrans==TRANS_WRITE );
assert( pBt->pPage1!=0 );
pP1 = pBt->pPage1->aData;
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
if( rc==SQLITE_OK ){
put4byte(&pP1[36 + idx*4], iMeta);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( idx==BTREE_INCR_VACUUM ){
assert( pBt->autoVacuum || iMeta==0 );
assert( iMeta==0 || iMeta==1 );
pBt->incrVacuum = (u8)iMeta;
}
#endif
}
sqlite3BtreeLeave(p);
return rc;
}
#ifndef SQLITE_OMIT_BTREECOUNT
/*
** The first argument, pCur, is a cursor opened on some b-tree. Count the
** number of entries in the b-tree and write the result to *pnEntry.
**
** SQLITE_OK is returned if the operation is successfully executed.
** Otherwise, if an error is encountered (i.e. an IO error or database
** corruption) an SQLite error code is returned.
*/
int sqlite3BtreeCount(BtCursor *pCur, i64 *pnEntry){
i64 nEntry = 0; /* Value to return in *pnEntry */
int rc; /* Return code */
if( pCur->pgnoRoot==0 ){
*pnEntry = 0;
return SQLITE_OK;
}
rc = moveToRoot(pCur);
/* Unless an error occurs, the following loop runs one iteration for each
** page in the B-Tree structure (not including overflow pages).
*/
while( rc==SQLITE_OK ){
int iIdx; /* Index of child node in parent */
MemPage *pPage; /* Current page of the b-tree */
/* If this is a leaf page or the tree is not an int-key tree, then
** this page contains countable entries. Increment the entry counter
** accordingly.
*/
pPage = pCur->apPage[pCur->iPage];
if( pPage->leaf || !pPage->intKey ){
nEntry += pPage->nCell;
}
/* pPage is a leaf node. This loop navigates the cursor so that it
** points to the first interior cell that it points to the parent of
** the next page in the tree that has not yet been visited. The
** pCur->aiIdx[pCur->iPage] value is set to the index of the parent cell
** of the page, or to the number of cells in the page if the next page
** to visit is the right-child of its parent.
**
** If all pages in the tree have been visited, return SQLITE_OK to the
** caller.
*/
if( pPage->leaf ){
do {
if( pCur->iPage==0 ){
/* All pages of the b-tree have been visited. Return successfully. */
*pnEntry = nEntry;
return moveToRoot(pCur);
}
moveToParent(pCur);
}while ( pCur->aiIdx[pCur->iPage]>=pCur->apPage[pCur->iPage]->nCell );
pCur->aiIdx[pCur->iPage]++;
pPage = pCur->apPage[pCur->iPage];
}
/* Descend to the child node of the cell that the cursor currently
** points at. This is the right-child if (iIdx==pPage->nCell).
*/
iIdx = pCur->aiIdx[pCur->iPage];
if( iIdx==pPage->nCell ){
rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
}else{
rc = moveToChild(pCur, get4byte(findCell(pPage, iIdx)));
}
}
/* An error has occurred. Return an error code. */
return rc;
}
#endif
/*
** Return the pager associated with a BTree. This routine is used for
** testing and debugging only.
*/
Pager *sqlite3BtreePager(Btree *p){
return p->pBt->pPager;
}
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Append a message to the error message string.
*/
static void checkAppendMsg(
IntegrityCk *pCheck,
const char *zFormat,
...
){
va_list ap;
if( !pCheck->mxErr ) return;
pCheck->mxErr--;
pCheck->nErr++;
va_start(ap, zFormat);
if( pCheck->errMsg.nChar ){
sqlite3StrAccumAppend(&pCheck->errMsg, "\n", 1);
}
if( pCheck->zPfx ){
sqlite3XPrintf(&pCheck->errMsg, pCheck->zPfx, pCheck->v1, pCheck->v2);
}
sqlite3VXPrintf(&pCheck->errMsg, zFormat, ap);
va_end(ap);
if( pCheck->errMsg.accError==STRACCUM_NOMEM ){
pCheck->mallocFailed = 1;
}
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Return non-zero if the bit in the IntegrityCk.aPgRef[] array that
** corresponds to page iPg is already set.
*/
static int getPageReferenced(IntegrityCk *pCheck, Pgno iPg){
assert( iPg<=pCheck->nPage && sizeof(pCheck->aPgRef[0])==1 );
return (pCheck->aPgRef[iPg/8] & (1 << (iPg & 0x07)));
}
/*
** Set the bit in the IntegrityCk.aPgRef[] array that corresponds to page iPg.
*/
static void setPageReferenced(IntegrityCk *pCheck, Pgno iPg){
assert( iPg<=pCheck->nPage && sizeof(pCheck->aPgRef[0])==1 );
pCheck->aPgRef[iPg/8] |= (1 << (iPg & 0x07));
}
/*
** Add 1 to the reference count for page iPage. If this is the second
** reference to the page, add an error message to pCheck->zErrMsg.
** Return 1 if there are 2 or more references to the page and 0 if
** if this is the first reference to the page.
**
** Also check that the page number is in bounds.
*/
static int checkRef(IntegrityCk *pCheck, Pgno iPage){
if( iPage==0 ) return 1;
if( iPage>pCheck->nPage ){
checkAppendMsg(pCheck, "invalid page number %d", iPage);
return 1;
}
if( getPageReferenced(pCheck, iPage) ){
checkAppendMsg(pCheck, "2nd reference to page %d", iPage);
return 1;
}
setPageReferenced(pCheck, iPage);
return 0;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Check that the entry in the pointer-map for page iChild maps to
** page iParent, pointer type ptrType. If not, append an error message
** to pCheck.
*/
static void checkPtrmap(
IntegrityCk *pCheck, /* Integrity check context */
Pgno iChild, /* Child page number */
u8 eType, /* Expected pointer map type */
Pgno iParent /* Expected pointer map parent page number */
){
int rc;
u8 ePtrmapType;
Pgno iPtrmapParent;
rc = ptrmapGet(pCheck->pBt, iChild, &ePtrmapType, &iPtrmapParent);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ) pCheck->mallocFailed = 1;
checkAppendMsg(pCheck, "Failed to read ptrmap key=%d", iChild);
return;
}
if( ePtrmapType!=eType || iPtrmapParent!=iParent ){
checkAppendMsg(pCheck,
"Bad ptr map entry key=%d expected=(%d,%d) got=(%d,%d)",
iChild, eType, iParent, ePtrmapType, iPtrmapParent);
}
}
#endif
/*
** Check the integrity of the freelist or of an overflow page list.
** Verify that the number of pages on the list is N.
*/
static void checkList(
IntegrityCk *pCheck, /* Integrity checking context */
int isFreeList, /* True for a freelist. False for overflow page list */
int iPage, /* Page number for first page in the list */
int N /* Expected number of pages in the list */
){
int i;
int expected = N;
int iFirst = iPage;
while( N-- > 0 && pCheck->mxErr ){
DbPage *pOvflPage;
unsigned char *pOvflData;
if( iPage<1 ){
checkAppendMsg(pCheck,
"%d of %d pages missing from overflow list starting at %d",
N+1, expected, iFirst);
break;
}
if( checkRef(pCheck, iPage) ) break;
if( sqlite3PagerGet(pCheck->pPager, (Pgno)iPage, &pOvflPage, 0) ){
checkAppendMsg(pCheck, "failed to get page %d", iPage);
break;
}
pOvflData = (unsigned char *)sqlite3PagerGetData(pOvflPage);
if( isFreeList ){
int n = get4byte(&pOvflData[4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pCheck->pBt->autoVacuum ){
checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0);
}
#endif
if( n>(int)pCheck->pBt->usableSize/4-2 ){
checkAppendMsg(pCheck,
"freelist leaf count too big on page %d", iPage);
N--;
}else{
for(i=0; i<n; i++){
Pgno iFreePage = get4byte(&pOvflData[8+i*4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pCheck->pBt->autoVacuum ){
checkPtrmap(pCheck, iFreePage, PTRMAP_FREEPAGE, 0);
}
#endif
checkRef(pCheck, iFreePage);
}
N -= n;
}
}
#ifndef SQLITE_OMIT_AUTOVACUUM
else{
/* If this database supports auto-vacuum and iPage is not the last
** page in this overflow list, check that the pointer-map entry for
** the following page matches iPage.
*/
if( pCheck->pBt->autoVacuum && N>0 ){
i = get4byte(pOvflData);
checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage);
}
}
#endif
iPage = get4byte(pOvflData);
sqlite3PagerUnref(pOvflPage);
if( isFreeList && N<(iPage!=0) ){
checkAppendMsg(pCheck, "free-page count in header is too small");
}
}
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
/*
** An implementation of a min-heap.
**
** aHeap[0] is the number of elements on the heap. aHeap[1] is the
** root element. The daughter nodes of aHeap[N] are aHeap[N*2]
** and aHeap[N*2+1].
**
** The heap property is this: Every node is less than or equal to both
** of its daughter nodes. A consequence of the heap property is that the
** root node aHeap[1] is always the minimum value currently in the heap.
**
** The btreeHeapInsert() routine inserts an unsigned 32-bit number onto
** the heap, preserving the heap property. The btreeHeapPull() routine
** removes the root element from the heap (the minimum value in the heap)
** and then moves other nodes around as necessary to preserve the heap
** property.
**
** This heap is used for cell overlap and coverage testing. Each u32
** entry represents the span of a cell or freeblock on a btree page.
** The upper 16 bits are the index of the first byte of a range and the
** lower 16 bits are the index of the last byte of that range.
*/
static void btreeHeapInsert(u32 *aHeap, u32 x){
u32 j, i = ++aHeap[0];
aHeap[i] = x;
while( (j = i/2)>0 && aHeap[j]>aHeap[i] ){
x = aHeap[j];
aHeap[j] = aHeap[i];
aHeap[i] = x;
i = j;
}
}
static int btreeHeapPull(u32 *aHeap, u32 *pOut){
u32 j, i, x;
if( (x = aHeap[0])==0 ) return 0;
*pOut = aHeap[1];
aHeap[1] = aHeap[x];
aHeap[x] = 0xffffffff;
aHeap[0]--;
i = 1;
while( (j = i*2)<=aHeap[0] ){
if( aHeap[j]>aHeap[j+1] ) j++;
if( aHeap[i]<aHeap[j] ) break;
x = aHeap[i];
aHeap[i] = aHeap[j];
aHeap[j] = x;
i = j;
}
return 1;
}
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** Do various sanity checks on a single page of a tree. Return
** the tree depth. Root pages return 0. Parents of root pages
** return 1, and so forth.
**
** These checks are done:
**
** 1. Make sure that cells and freeblocks do not overlap
** but combine to completely cover the page.
** 2. Make sure integer cell keys are in order.
** 3. Check the integrity of overflow pages.
** 4. Recursively call checkTreePage on all children.
** 5. Verify that the depth of all children is the same.
*/
static int checkTreePage(
IntegrityCk *pCheck, /* Context for the sanity check */
int iPage, /* Page number of the page to check */
i64 *piMinKey, /* Write minimum integer primary key here */
i64 maxKey /* Error if integer primary key greater than this */
){
MemPage *pPage = 0; /* The page being analyzed */
int i; /* Loop counter */
int rc; /* Result code from subroutine call */
int depth = -1, d2; /* Depth of a subtree */
int pgno; /* Page number */
int nFrag; /* Number of fragmented bytes on the page */
int hdr; /* Offset to the page header */
int cellStart; /* Offset to the start of the cell pointer array */
int nCell; /* Number of cells */
int doCoverageCheck = 1; /* True if cell coverage checking should be done */
int keyCanBeEqual = 1; /* True if IPK can be equal to maxKey
** False if IPK must be strictly less than maxKey */
u8 *data; /* Page content */
u8 *pCell; /* Cell content */
u8 *pCellIdx; /* Next element of the cell pointer array */
BtShared *pBt; /* The BtShared object that owns pPage */
u32 pc; /* Address of a cell */
u32 usableSize; /* Usable size of the page */
u32 contentOffset; /* Offset to the start of the cell content area */
u32 *heap = 0; /* Min-heap used for checking cell coverage */
u32 x, prev = 0; /* Next and previous entry on the min-heap */
const char *saved_zPfx = pCheck->zPfx;
int saved_v1 = pCheck->v1;
int saved_v2 = pCheck->v2;
u8 savedIsInit = 0;
/* Check that the page exists
*/
pBt = pCheck->pBt;
usableSize = pBt->usableSize;
if( iPage==0 ) return 0;
if( checkRef(pCheck, iPage) ) return 0;
pCheck->zPfx = "Page %d: ";
pCheck->v1 = iPage;
if( (rc = btreeGetPage(pBt, (Pgno)iPage, &pPage, 0))!=0 ){
checkAppendMsg(pCheck,
"unable to get the page. error code=%d", rc);
goto end_of_check;
}
/* Clear MemPage.isInit to make sure the corruption detection code in
** btreeInitPage() is executed. */
savedIsInit = pPage->isInit;
pPage->isInit = 0;
if( (rc = btreeInitPage(pPage))!=0 ){
assert( rc==SQLITE_CORRUPT ); /* The only possible error from InitPage */
checkAppendMsg(pCheck,
"btreeInitPage() returns error code %d", rc);
goto end_of_check;
}
data = pPage->aData;
hdr = pPage->hdrOffset;
/* Set up for cell analysis */
pCheck->zPfx = "On tree page %d cell %d: ";
contentOffset = get2byteNotZero(&data[hdr+5]);
assert( contentOffset<=usableSize ); /* Enforced by btreeInitPage() */
/* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
** number of cells on the page. */
nCell = get2byte(&data[hdr+3]);
assert( pPage->nCell==nCell );
/* EVIDENCE-OF: R-23882-45353 The cell pointer array of a b-tree page
** immediately follows the b-tree page header. */
cellStart = hdr + 12 - 4*pPage->leaf;
assert( pPage->aCellIdx==&data[cellStart] );
pCellIdx = &data[cellStart + 2*(nCell-1)];
if( !pPage->leaf ){
/* Analyze the right-child page of internal pages */
pgno = get4byte(&data[hdr+8]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
pCheck->zPfx = "On page %d at right child: ";
checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
}
#endif
depth = checkTreePage(pCheck, pgno, &maxKey, maxKey);
keyCanBeEqual = 0;
}else{
/* For leaf pages, the coverage check will occur in the same loop
** as the other cell checks, so initialize the heap. */
heap = pCheck->heap;
heap[0] = 0;
}
/* EVIDENCE-OF: R-02776-14802 The cell pointer array consists of K 2-byte
** integer offsets to the cell contents. */
for(i=nCell-1; i>=0 && pCheck->mxErr; i--){
CellInfo info;
/* Check cell size */
pCheck->v2 = i;
assert( pCellIdx==&data[cellStart + i*2] );
pc = get2byteAligned(pCellIdx);
pCellIdx -= 2;
if( pc<contentOffset || pc>usableSize-4 ){
checkAppendMsg(pCheck, "Offset %d out of range %d..%d",
pc, contentOffset, usableSize-4);
doCoverageCheck = 0;
continue;
}
pCell = &data[pc];
pPage->xParseCell(pPage, pCell, &info);
if( pc+info.nSize>usableSize ){
checkAppendMsg(pCheck, "Extends off end of page");
doCoverageCheck = 0;
continue;
}
/* Check for integer primary key out of range */
if( pPage->intKey ){
if( keyCanBeEqual ? (info.nKey > maxKey) : (info.nKey >= maxKey) ){
checkAppendMsg(pCheck, "Rowid %lld out of order", info.nKey);
}
maxKey = info.nKey;
}
/* Check the content overflow list */
if( info.nPayload>info.nLocal ){
int nPage; /* Number of pages on the overflow chain */
Pgno pgnoOvfl; /* First page of the overflow chain */
assert( pc + info.nSize - 4 <= usableSize );
nPage = (info.nPayload - info.nLocal + usableSize - 5)/(usableSize - 4);
pgnoOvfl = get4byte(&pCell[info.nSize - 4]);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage);
}
#endif
checkList(pCheck, 0, pgnoOvfl, nPage);
}
if( !pPage->leaf ){
/* Check sanity of left child page for internal pages */
pgno = get4byte(pCell);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum ){
checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
}
#endif
d2 = checkTreePage(pCheck, pgno, &maxKey, maxKey);
keyCanBeEqual = 0;
if( d2!=depth ){
checkAppendMsg(pCheck, "Child page depth differs");
depth = d2;
}
}else{
/* Populate the coverage-checking heap for leaf pages */
btreeHeapInsert(heap, (pc<<16)|(pc+info.nSize-1));
}
}
*piMinKey = maxKey;
/* Check for complete coverage of the page
*/
pCheck->zPfx = 0;
if( doCoverageCheck && pCheck->mxErr>0 ){
/* For leaf pages, the min-heap has already been initialized and the
** cells have already been inserted. But for internal pages, that has
** not yet been done, so do it now */
if( !pPage->leaf ){
heap = pCheck->heap;
heap[0] = 0;
for(i=nCell-1; i>=0; i--){
u32 size;
pc = get2byteAligned(&data[cellStart+i*2]);
size = pPage->xCellSize(pPage, &data[pc]);
btreeHeapInsert(heap, (pc<<16)|(pc+size-1));
}
}
/* Add the freeblocks to the min-heap
**
** EVIDENCE-OF: R-20690-50594 The second field of the b-tree page header
** is the offset of the first freeblock, or zero if there are no
** freeblocks on the page.
*/
i = get2byte(&data[hdr+1]);
while( i>0 ){
int size, j;
assert( (u32)i<=usableSize-4 ); /* Enforced by btreeInitPage() */
size = get2byte(&data[i+2]);
assert( (u32)(i+size)<=usableSize ); /* Enforced by btreeInitPage() */
btreeHeapInsert(heap, (((u32)i)<<16)|(i+size-1));
/* EVIDENCE-OF: R-58208-19414 The first 2 bytes of a freeblock are a
** big-endian integer which is the offset in the b-tree page of the next
** freeblock in the chain, or zero if the freeblock is the last on the
** chain. */
j = get2byte(&data[i]);
/* EVIDENCE-OF: R-06866-39125 Freeblocks are always connected in order of
** increasing offset. */
assert( j==0 || j>i+size ); /* Enforced by btreeInitPage() */
assert( (u32)j<=usableSize-4 ); /* Enforced by btreeInitPage() */
i = j;
}
/* Analyze the min-heap looking for overlap between cells and/or
** freeblocks, and counting the number of untracked bytes in nFrag.
**
** Each min-heap entry is of the form: (start_address<<16)|end_address.
** There is an implied first entry the covers the page header, the cell
** pointer index, and the gap between the cell pointer index and the start
** of cell content.
**
** The loop below pulls entries from the min-heap in order and compares
** the start_address against the previous end_address. If there is an
** overlap, that means bytes are used multiple times. If there is a gap,
** that gap is added to the fragmentation count.
*/
nFrag = 0;
prev = contentOffset - 1; /* Implied first min-heap entry */
while( btreeHeapPull(heap,&x) ){
if( (prev&0xffff)>=(x>>16) ){
checkAppendMsg(pCheck,
"Multiple uses for byte %u of page %d", x>>16, iPage);
break;
}else{
nFrag += (x>>16) - (prev&0xffff) - 1;
prev = x;
}
}
nFrag += usableSize - (prev&0xffff) - 1;
/* EVIDENCE-OF: R-43263-13491 The total number of bytes in all fragments
** is stored in the fifth field of the b-tree page header.
** EVIDENCE-OF: R-07161-27322 The one-byte integer at offset 7 gives the
** number of fragmented free bytes within the cell content area.
*/
if( heap[0]==0 && nFrag!=data[hdr+7] ){
checkAppendMsg(pCheck,
"Fragmentation of %d bytes reported as %d on page %d",
nFrag, data[hdr+7], iPage);
}
}
end_of_check:
if( !doCoverageCheck ) pPage->isInit = savedIsInit;
releasePage(pPage);
pCheck->zPfx = saved_zPfx;
pCheck->v1 = saved_v1;
pCheck->v2 = saved_v2;
return depth+1;
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
#ifndef SQLITE_OMIT_INTEGRITY_CHECK
/*
** This routine does a complete check of the given BTree file. aRoot[] is
** an array of pages numbers were each page number is the root page of
** a table. nRoot is the number of entries in aRoot.
**
** A read-only or read-write transaction must be opened before calling
** this function.
**
** Write the number of error seen in *pnErr. Except for some memory
** allocation errors, an error message held in memory obtained from
** malloc is returned if *pnErr is non-zero. If *pnErr==0 then NULL is
** returned. If a memory allocation error occurs, NULL is returned.
*/
char *sqlite3BtreeIntegrityCheck(
Btree *p, /* The btree to be checked */
int *aRoot, /* An array of root pages numbers for individual trees */
int nRoot, /* Number of entries in aRoot[] */
int mxErr, /* Stop reporting errors after this many */
int *pnErr /* Write number of errors seen to this variable */
){
Pgno i;
IntegrityCk sCheck;
BtShared *pBt = p->pBt;
int savedDbFlags = pBt->db->flags;
char zErr[100];
VVA_ONLY( int nRef );
sqlite3BtreeEnter(p);
assert( p->inTrans>TRANS_NONE && pBt->inTransaction>TRANS_NONE );
VVA_ONLY( nRef = sqlite3PagerRefcount(pBt->pPager) );
assert( nRef>=0 );
sCheck.pBt = pBt;
sCheck.pPager = pBt->pPager;
sCheck.nPage = btreePagecount(sCheck.pBt);
sCheck.mxErr = mxErr;
sCheck.nErr = 0;
sCheck.mallocFailed = 0;
sCheck.zPfx = 0;
sCheck.v1 = 0;
sCheck.v2 = 0;
sCheck.aPgRef = 0;
sCheck.heap = 0;
sqlite3StrAccumInit(&sCheck.errMsg, 0, zErr, sizeof(zErr), SQLITE_MAX_LENGTH);
sCheck.errMsg.printfFlags = SQLITE_PRINTF_INTERNAL;
if( sCheck.nPage==0 ){
goto integrity_ck_cleanup;
}
sCheck.aPgRef = sqlite3MallocZero((sCheck.nPage / 8)+ 1);
if( !sCheck.aPgRef ){
sCheck.mallocFailed = 1;
goto integrity_ck_cleanup;
}
sCheck.heap = (u32*)sqlite3PageMalloc( pBt->pageSize );
if( sCheck.heap==0 ){
sCheck.mallocFailed = 1;
goto integrity_ck_cleanup;
}
i = PENDING_BYTE_PAGE(pBt);
if( i<=sCheck.nPage ) setPageReferenced(&sCheck, i);
/* Check the integrity of the freelist
*/
sCheck.zPfx = "Main freelist: ";
checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
get4byte(&pBt->pPage1->aData[36]));
sCheck.zPfx = 0;
/* Check all the tables.
*/
testcase( pBt->db->flags & SQLITE_CellSizeCk );
pBt->db->flags &= ~SQLITE_CellSizeCk;
for(i=0; (int)i<nRoot && sCheck.mxErr; i++){
i64 notUsed;
if( aRoot[i]==0 ) continue;
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pBt->autoVacuum && aRoot[i]>1 ){
checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0);
}
#endif
checkTreePage(&sCheck, aRoot[i], ¬Used, LARGEST_INT64);
}
pBt->db->flags = savedDbFlags;
/* Make sure every page in the file is referenced
*/
for(i=1; i<=sCheck.nPage && sCheck.mxErr; i++){
#ifdef SQLITE_OMIT_AUTOVACUUM
if( getPageReferenced(&sCheck, i)==0 ){
checkAppendMsg(&sCheck, "Page %d is never used", i);
}
#else
/* If the database supports auto-vacuum, make sure no tables contain
** references to pointer-map pages.
*/
if( getPageReferenced(&sCheck, i)==0 &&
(PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
checkAppendMsg(&sCheck, "Page %d is never used", i);
}
if( getPageReferenced(&sCheck, i)!=0 &&
(PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
checkAppendMsg(&sCheck, "Pointer map page %d is referenced", i);
}
#endif
}
/* Clean up and report errors.
*/
integrity_ck_cleanup:
sqlite3PageFree(sCheck.heap);
sqlite3_free(sCheck.aPgRef);
if( sCheck.mallocFailed ){
sqlite3StrAccumReset(&sCheck.errMsg);
sCheck.nErr++;
}
*pnErr = sCheck.nErr;
if( sCheck.nErr==0 ) sqlite3StrAccumReset(&sCheck.errMsg);
/* Make sure this analysis did not leave any unref() pages. */
assert( nRef==sqlite3PagerRefcount(pBt->pPager) );
sqlite3BtreeLeave(p);
return sqlite3StrAccumFinish(&sCheck.errMsg);
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
/*
** Return the full pathname of the underlying database file. Return
** an empty string if the database is in-memory or a TEMP database.
**
** The pager filename is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite3BtreeGetFilename(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3PagerFilename(p->pBt->pPager, 1);
}
/*
** Return the pathname of the journal file for this database. The return
** value of this routine is the same regardless of whether the journal file
** has been created or not.
**
** The pager journal filename is invariant as long as the pager is
** open so it is safe to access without the BtShared mutex.
*/
const char *sqlite3BtreeGetJournalname(Btree *p){
assert( p->pBt->pPager!=0 );
return sqlite3PagerJournalname(p->pBt->pPager);
}
/*
** Return non-zero if a transaction is active.
*/
int sqlite3BtreeIsInTrans(Btree *p){
assert( p==0 || sqlite3_mutex_held(p->db->mutex) );
return (p && (p->inTrans==TRANS_WRITE));
}
#ifndef SQLITE_OMIT_WAL
/*
** Run a checkpoint on the Btree passed as the first argument.
**
** Return SQLITE_LOCKED if this or any other connection has an open
** transaction on the shared-cache the argument Btree is connected to.
**
** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
*/
int sqlite3BtreeCheckpoint(Btree *p, int eMode, int *pnLog, int *pnCkpt){
int rc = SQLITE_OK;
if( p ){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( pBt->inTransaction!=TRANS_NONE ){
rc = SQLITE_LOCKED;
}else{
rc = sqlite3PagerCheckpoint(pBt->pPager, eMode, pnLog, pnCkpt);
}
sqlite3BtreeLeave(p);
}
return rc;
}
#endif
/*
** Return non-zero if a read (or write) transaction is active.
*/
int sqlite3BtreeIsInReadTrans(Btree *p){
assert( p );
assert( sqlite3_mutex_held(p->db->mutex) );
return p->inTrans!=TRANS_NONE;
}
int sqlite3BtreeIsInBackup(Btree *p){
assert( p );
assert( sqlite3_mutex_held(p->db->mutex) );
return p->nBackup!=0;
}
/*
** This function returns a pointer to a blob of memory associated with
** a single shared-btree. The memory is used by client code for its own
** purposes (for example, to store a high-level schema associated with
** the shared-btree). The btree layer manages reference counting issues.
**
** The first time this is called on a shared-btree, nBytes bytes of memory
** are allocated, zeroed, and returned to the caller. For each subsequent
** call the nBytes parameter is ignored and a pointer to the same blob
** of memory returned.
**
** If the nBytes parameter is 0 and the blob of memory has not yet been
** allocated, a null pointer is returned. If the blob has already been
** allocated, it is returned as normal.
**
** Just before the shared-btree is closed, the function passed as the
** xFree argument when the memory allocation was made is invoked on the
** blob of allocated memory. The xFree function should not call sqlite3_free()
** on the memory, the btree layer does that.
*/
void *sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
BtShared *pBt = p->pBt;
sqlite3BtreeEnter(p);
if( !pBt->pSchema && nBytes ){
pBt->pSchema = sqlite3DbMallocZero(0, nBytes);
pBt->xFreeSchema = xFree;
}
sqlite3BtreeLeave(p);
return pBt->pSchema;
}
/*
** Return SQLITE_LOCKED_SHAREDCACHE if another user of the same shared
** btree as the argument handle holds an exclusive lock on the
** sqlite_master table. Otherwise SQLITE_OK.
*/
int sqlite3BtreeSchemaLocked(Btree *p){
int rc;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);
assert( rc==SQLITE_OK || rc==SQLITE_LOCKED_SHAREDCACHE );
sqlite3BtreeLeave(p);
return rc;
}
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** Obtain a lock on the table whose root page is iTab. The
** lock is a write lock if isWritelock is true or a read lock
** if it is false.
*/
int sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
int rc = SQLITE_OK;
assert( p->inTrans!=TRANS_NONE );
if( p->sharable ){
u8 lockType = READ_LOCK + isWriteLock;
assert( READ_LOCK+1==WRITE_LOCK );
assert( isWriteLock==0 || isWriteLock==1 );
sqlite3BtreeEnter(p);
rc = querySharedCacheTableLock(p, iTab, lockType);
if( rc==SQLITE_OK ){
rc = setSharedCacheTableLock(p, iTab, lockType);
}
sqlite3BtreeLeave(p);
}
return rc;
}
#endif
#ifndef SQLITE_OMIT_INCRBLOB
/*
** Argument pCsr must be a cursor opened for writing on an
** INTKEY table currently pointing at a valid table entry.
** This function modifies the data stored as part of that entry.
**
** Only the data content may only be modified, it is not possible to
** change the length of the data stored. If this function is called with
** parameters that attempt to write past the end of the existing data,
** no modifications are made and SQLITE_CORRUPT is returned.
*/
int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
int rc;
assert( cursorOwnsBtShared(pCsr) );
assert( sqlite3_mutex_held(pCsr->pBtree->db->mutex) );
assert( pCsr->curFlags & BTCF_Incrblob );
rc = restoreCursorPosition(pCsr);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pCsr->eState!=CURSOR_REQUIRESEEK );
if( pCsr->eState!=CURSOR_VALID ){
return SQLITE_ABORT;
}
/* Save the positions of all other cursors open on this table. This is
** required in case any of them are holding references to an xFetch
** version of the b-tree page modified by the accessPayload call below.
**
** Note that pCsr must be open on a INTKEY table and saveCursorPosition()
** and hence saveAllCursors() cannot fail on a BTREE_INTKEY table, hence
** saveAllCursors can only return SQLITE_OK.
*/
VVA_ONLY(rc =) saveAllCursors(pCsr->pBt, pCsr->pgnoRoot, pCsr);
assert( rc==SQLITE_OK );
/* Check some assumptions:
** (a) the cursor is open for writing,
** (b) there is a read/write transaction open,
** (c) the connection holds a write-lock on the table (if required),
** (d) there are no conflicting read-locks, and
** (e) the cursor points at a valid row of an intKey table.
*/
if( (pCsr->curFlags & BTCF_WriteFlag)==0 ){
return SQLITE_READONLY;
}
assert( (pCsr->pBt->btsFlags & BTS_READ_ONLY)==0
&& pCsr->pBt->inTransaction==TRANS_WRITE );
assert( hasSharedCacheTableLock(pCsr->pBtree, pCsr->pgnoRoot, 0, 2) );
assert( !hasReadConflicts(pCsr->pBtree, pCsr->pgnoRoot) );
assert( pCsr->apPage[pCsr->iPage]->intKey );
return accessPayload(pCsr, offset, amt, (unsigned char *)z, 1);
}
/*
** Mark this cursor as an incremental blob cursor.
*/
void sqlite3BtreeIncrblobCursor(BtCursor *pCur){
pCur->curFlags |= BTCF_Incrblob;
pCur->pBtree->hasIncrblobCur = 1;
}
#endif
/*
** Set both the "read version" (single byte at byte offset 18) and
** "write version" (single byte at byte offset 19) fields in the database
** header to iVersion.
*/
int sqlite3BtreeSetVersion(Btree *pBtree, int iVersion){
BtShared *pBt = pBtree->pBt;
int rc; /* Return code */
assert( iVersion==1 || iVersion==2 );
/* If setting the version fields to 1, do not automatically open the
** WAL connection, even if the version fields are currently set to 2.
*/
pBt->btsFlags &= ~BTS_NO_WAL;
if( iVersion==1 ) pBt->btsFlags |= BTS_NO_WAL;
rc = sqlite3BtreeBeginTrans(pBtree, 0);
if( rc==SQLITE_OK ){
u8 *aData = pBt->pPage1->aData;
if( aData[18]!=(u8)iVersion || aData[19]!=(u8)iVersion ){
rc = sqlite3BtreeBeginTrans(pBtree, 2);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
if( rc==SQLITE_OK ){
aData[18] = (u8)iVersion;
aData[19] = (u8)iVersion;
}
}
}
}
pBt->btsFlags &= ~BTS_NO_WAL;
return rc;
}
/*
** Return true if the cursor has a hint specified. This routine is
** only used from within assert() statements
*/
int sqlite3BtreeCursorHasHint(BtCursor *pCsr, unsigned int mask){
return (pCsr->hints & mask)!=0;
}
/*
** Return true if the given Btree is read-only.
*/
int sqlite3BtreeIsReadonly(Btree *p){
return (p->pBt->btsFlags & BTS_READ_ONLY)!=0;
}
/*
** Return the size of the header added to each page by this module.
*/
int sqlite3HeaderSizeBtree(void){ return ROUND8(sizeof(MemPage)); }
#if !defined(SQLITE_OMIT_SHARED_CACHE)
/*
** Return true if the Btree passed as the only argument is sharable.
*/
int sqlite3BtreeSharable(Btree *p){
return p->sharable;
}
/*
** Return the number of connections to the BtShared object accessed by
** the Btree handle passed as the only argument. For private caches
** this is always 1. For shared caches it may be 1 or greater.
*/
int sqlite3BtreeConnectionCount(Btree *p){
testcase( p->sharable );
return p->pBt->nRef;
}
#endif