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Overview
Comment:More locking fixes. Now makes it all the way through quick.test. There are errors but no assertion faults. Progress. (CVS 4319)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 844d40b8379d3374130e2d94f6e32c2cda34e0ca
User & Date: drh 2007-08-29 00:33:07
Context
2007-08-29
04:00
Better asserts(). But now some of the tests are busted again. (CVS 4320) check-in: e8060f85 user: drh tags: trunk
00:33
More locking fixes. Now makes it all the way through quick.test. There are errors but no assertion faults. Progress. (CVS 4319) check-in: 844d40b8 user: drh tags: trunk
2007-08-28
23:28
The shared_err test runs with no errors. But a potential deadlock has been discovered and is still unfixed. (CVS 4318) check-in: f093a0d7 user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/btmutex.c.

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**
**    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.
**
*************************************************************************
**
** $Id: btmutex.c,v 1.3 2007/08/28 23:28:08 drh Exp $
**
** This file contains code used to implement mutexes on Btree objects.
** This code really belongs in btree.c.  But btree.c is getting too
** big and we want to break it down some.  This packaged seemed like
** a good breakout.
*/
#include "btreeInt.h"
................................................................................
    if( p->wantToLock==0 ){
      assert( p->locked );
      sqlite3_mutex_leave(p->pBt->mutex);
      p->locked = 0;
    }
  }
}
























































/*
** Potentially dd a new Btree pointer to a BtreeMutexArray.
** Really only add the Btree if it can possibly be shared with
** another database connection.
**
** The Btrees are kept in sorted order by pBtree->pBt.  That
................................................................................
** way when we go to enter all the mutexes, we can enter them
** in order without every having to backup and retry and without
** worrying about deadlock.
**
** The number of shared btrees will always be small (usually 0 or 1)
** so an insertion sort is an adequate algorithm here.
*/
void sqlite3BtreeMutexArrayInsert(BtreeMutexArray *pSet, Btree *pBtree){
  int i, j;
  BtShared *pBt;
  if( !pBtree->sharable ) return;
#ifndef NDEBUG
  {
    for(i=0; i<pSet->nMutex; i++){
      assert( pSet->aBtree[i]!=pBtree );
    }
  }
#endif
  assert( pSet->nMutex>=0 );
  assert( pSet->nMutex<sizeof(pSet->aBtree)/sizeof(pSet->aBtree[0])-1 );
  pBt = pBtree->pBt;
  for(i=0; i<pSet->nMutex; i++){
    assert( pSet->aBtree[i]!=pBtree );
    if( pSet->aBtree[i]->pBt>pBt ){
      for(j=pSet->nMutex; j>i; j--){
        pSet->aBtree[j] = pSet->aBtree[j-1];
      }
      pSet->aBtree[i] = pBtree;

      return;
    }
  }
  pSet->aBtree[pSet->nMutex++] = pBtree;
}

/*
** Enter the mutex of every btree in the array.  This routine is
** called at the beginning of sqlite3VdbeExec().  The mutexes are
** exited at the end of the same function.
*/
void sqlite3BtreeMutexArrayEnter(BtreeMutexArray *pSet){
  int i;
  for(i=0; i<pSet->nMutex; i++){
    Btree *p = pSet->aBtree[i];
    /* Some basic sanity checking */
    assert( i==0 || pSet->aBtree[i-1]->pBt<p->pBt );
    assert( !p->locked || p->wantToLock>0 );
    assert( p->sharable );

    /* We should already hold a lock on the database connection */
    assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );

    p->wantToLock++;
................................................................................
    }
  }
}

/*
** Leave the mutex of every btree in the group.
*/
void sqlite3BtreeMutexArrayLeave(BtreeMutexArray *pSet){
  int i;
  for(i=0; i<pSet->nMutex; i++){
    Btree *p = pSet->aBtree[i];
    /* Some basic sanity checking */
    assert( i==0 || pSet->aBtree[i-1]->pBt<p->pBt );
    assert( p->locked );
    assert( p->sharable );
    assert( p->wantToLock>0 );

    /* We should already hold a lock on the database connection */
    assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );








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**
**    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.
**
*************************************************************************
**
** $Id: btmutex.c,v 1.4 2007/08/29 00:33:07 drh Exp $
**
** This file contains code used to implement mutexes on Btree objects.
** This code really belongs in btree.c.  But btree.c is getting too
** big and we want to break it down some.  This packaged seemed like
** a good breakout.
*/
#include "btreeInt.h"
................................................................................
    if( p->wantToLock==0 ){
      assert( p->locked );
      sqlite3_mutex_leave(p->pBt->mutex);
      p->locked = 0;
    }
  }
}

/*
** Enter the mutex on every Btree associated with a database
** connection.  This is needed (for example) prior to parsing
** a statement since we will be comparing table and column names
** against all schemas and we do not want those schemas being
** reset out from under us.
**
** There is a corresponding leave-all procedures.
**
** Enter the mutexes in accending order by BtShared pointer address
** to avoid the possibility of deadlock when two threads with
** two or more btrees in common both try to lock all their btrees
** at the same instant.
*/
void sqlite3BtreeEnterAll(sqlite3 *db){
  int i;
  Btree *p;
  assert( sqlite3_mutex_held(db->mutex) );
  for(i=0; i<db->nDb && ((p = db->aDb[i].pBt)==0 || p->sharable==0); i++){}
  if( i<db->nDb ){
    while( p->pNext ) p = p->pNext;
    while( 1 ){
      if( p->locked ){
        sqlite3_mutex_leave(p->pBt->mutex);
        p->locked = 0;
      }
      if( p->pPrev==0 ) break;
      p = p->pPrev;
    }
    while( p ){
      p->wantToLock++;
      sqlite3_mutex_enter(p->pBt->mutex);
      p->locked = 1;
      p = p->pNext;
    }
  }
}
void sqlite3BtreeLeaveAll(sqlite3 *db){
  int i;
  Btree *p;
  assert( sqlite3_mutex_held(db->mutex) );
  for(i=0; i<db->nDb && ((p = db->aDb[i].pBt)==0 || p->sharable==0); i++){}
  if( i<db->nDb ){
    while( p->pPrev ) p = p->pPrev;
    while( p ){
      p->wantToLock--;
      if( p->wantToLock==0 ){
        sqlite3_mutex_leave(p->pBt->mutex);
        p->locked = 0;
      }
      p = p->pNext;
    }
  }
}

/*
** Potentially dd a new Btree pointer to a BtreeMutexArray.
** Really only add the Btree if it can possibly be shared with
** another database connection.
**
** The Btrees are kept in sorted order by pBtree->pBt.  That
................................................................................
** way when we go to enter all the mutexes, we can enter them
** in order without every having to backup and retry and without
** worrying about deadlock.
**
** The number of shared btrees will always be small (usually 0 or 1)
** so an insertion sort is an adequate algorithm here.
*/
void sqlite3BtreeMutexArrayInsert(BtreeMutexArray *pArray, Btree *pBtree){
  int i, j;
  BtShared *pBt;
  if( !pBtree->sharable ) return;
#ifndef NDEBUG
  {
    for(i=0; i<pArray->nMutex; i++){
      assert( pArray->aBtree[i]!=pBtree );
    }
  }
#endif
  assert( pArray->nMutex>=0 );
  assert( pArray->nMutex<sizeof(pArray->aBtree)/sizeof(pArray->aBtree[0])-1 );
  pBt = pBtree->pBt;
  for(i=0; i<pArray->nMutex; i++){
    assert( pArray->aBtree[i]!=pBtree );
    if( pArray->aBtree[i]->pBt>pBt ){
      for(j=pArray->nMutex; j>i; j--){
        pArray->aBtree[j] = pArray->aBtree[j-1];
      }
      pArray->aBtree[i] = pBtree;
      pArray->nMutex++;
      return;
    }
  }
  pArray->aBtree[pArray->nMutex++] = pBtree;
}

/*
** Enter the mutex of every btree in the array.  This routine is
** called at the beginning of sqlite3VdbeExec().  The mutexes are
** exited at the end of the same function.
*/
void sqlite3BtreeMutexArrayEnter(BtreeMutexArray *pArray){
  int i;
  for(i=0; i<pArray->nMutex; i++){
    Btree *p = pArray->aBtree[i];
    /* Some basic sanity checking */
    assert( i==0 || pArray->aBtree[i-1]->pBt<p->pBt );
    assert( !p->locked || p->wantToLock>0 );
    assert( p->sharable );

    /* We should already hold a lock on the database connection */
    assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );

    p->wantToLock++;
................................................................................
    }
  }
}

/*
** Leave the mutex of every btree in the group.
*/
void sqlite3BtreeMutexArrayLeave(BtreeMutexArray *pArray){
  int i;
  for(i=0; i<pArray->nMutex; i++){
    Btree *p = pArray->aBtree[i];
    /* Some basic sanity checking */
    assert( i==0 || pArray->aBtree[i-1]->pBt<p->pBt );
    assert( p->locked );
    assert( p->sharable );
    assert( p->wantToLock>0 );

    /* We should already hold a lock on the database connection */
    assert( sqlite3BtreeMutexHeld(p->pSqlite->mutex) );

Changes to src/btree.h.

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**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite B-Tree file
** subsystem.  See comments in the source code for a detailed description
** of what each interface routine does.
**
** @(#) $Id: btree.h,v 1.88 2007/08/28 23:28:08 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/* TODO: This definition is just included so other modules compile. It
** needs to be revisited.
*/
................................................................................
int sqlite3BtreeIsInTrans(Btree*);
int sqlite3BtreeIsInStmt(Btree*);
int sqlite3BtreeIsInReadTrans(Btree*);
void *sqlite3BtreeSchema(Btree *, int, void(*)(void *));
int sqlite3BtreeSchemaLocked(Btree *);
int sqlite3BtreeLockTable(Btree *, int, u8);

/*
** If we are not using shared cache, then there is no need to
** use mutexes to access the BtShared structures.  So make the
** Enter and Leave procedures no-ops.
*/
#if SQLITE_THREADSAFE && !defined(SQLITE_OMIT_SHARED_CACHE)
  void sqlite3BtreeEnter(Btree*);
  void sqlite3BtreeLeave(Btree*);
# define sqlite3BtreeMutexHeld(X) sqlite3_mutex_held(X)
#else
# define sqlite3BtreeEnter(X)
# define sqlite3BtreeLeave(X)
# define sqlite3BtreeMutexHeld(X) 1
#endif

const char *sqlite3BtreeGetFilename(Btree *);
const char *sqlite3BtreeGetDirname(Btree *);
const char *sqlite3BtreeGetJournalname(Btree *);
int sqlite3BtreeCopyFile(Btree *, Btree *);

int sqlite3BtreeIncrVacuum(Btree *);

................................................................................

#ifdef SQLITE_TEST
int sqlite3BtreeCursorInfo(BtCursor*, int*, int);
void sqlite3BtreeCursorList(Btree*);
int sqlite3BtreePageDump(Btree*, int, int recursive);
#endif






#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE





  void sqlite3BtreeMutexArrayEnter(BtreeMutexArray*);
  void sqlite3BtreeMutexArrayLeave(BtreeMutexArray*);
  void sqlite3BtreeMutexArrayInsert(BtreeMutexArray*, Btree*);
#else





# define sqlite3BtreeMutexArrayEnter(X)
# define sqlite3BtreeMutexArrayLeave(X)
# define sqlite3BtreeMutexArrayInsert(X,Y)
#endif



#endif /* _BTREE_H_ */







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**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite B-Tree file
** subsystem.  See comments in the source code for a detailed description
** of what each interface routine does.
**
** @(#) $Id: btree.h,v 1.89 2007/08/29 00:33:07 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/* TODO: This definition is just included so other modules compile. It
** needs to be revisited.
*/
................................................................................
int sqlite3BtreeIsInTrans(Btree*);
int sqlite3BtreeIsInStmt(Btree*);
int sqlite3BtreeIsInReadTrans(Btree*);
void *sqlite3BtreeSchema(Btree *, int, void(*)(void *));
int sqlite3BtreeSchemaLocked(Btree *);
int sqlite3BtreeLockTable(Btree *, int, u8);
















const char *sqlite3BtreeGetFilename(Btree *);
const char *sqlite3BtreeGetDirname(Btree *);
const char *sqlite3BtreeGetJournalname(Btree *);
int sqlite3BtreeCopyFile(Btree *, Btree *);

int sqlite3BtreeIncrVacuum(Btree *);

................................................................................

#ifdef SQLITE_TEST
int sqlite3BtreeCursorInfo(BtCursor*, int*, int);
void sqlite3BtreeCursorList(Btree*);
int sqlite3BtreePageDump(Btree*, int, int recursive);
#endif

/*
** If we are not using shared cache, then there is no need to
** use mutexes to access the BtShared structures.  So make the
** Enter and Leave procedures no-ops.
*/
#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE
  void sqlite3BtreeEnter(Btree*);
  void sqlite3BtreeLeave(Btree*);
# define sqlite3BtreeMutexHeld(X) sqlite3_mutex_held(X)
  void sqlite3BtreeEnterAll(sqlite3*);
  void sqlite3BtreeLeaveAll(sqlite3*);
  void sqlite3BtreeMutexArrayEnter(BtreeMutexArray*);
  void sqlite3BtreeMutexArrayLeave(BtreeMutexArray*);
  void sqlite3BtreeMutexArrayInsert(BtreeMutexArray*, Btree*);
#else
# define sqlite3BtreeEnter(X)
# define sqlite3BtreeLeave(X)
# define sqlite3BtreeMutexHeld(X) 1
# define sqlite3BtreeEnterAll(X)
# define sqlite3BtreeLeaveAll(X)
# define sqlite3BtreeMutexArrayEnter(X)
# define sqlite3BtreeMutexArrayLeave(X)
# define sqlite3BtreeMutexArrayInsert(X,Y)
#endif



#endif /* _BTREE_H_ */

Changes to src/btreeInt.h.

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** 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.
**
*************************************************************************
** $Id: btreeInt.h,v 1.11 2007/08/28 22:24:35 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
................................................................................
struct Btree {
  sqlite3 *pSqlite;  /* The database connection holding this btree */
  BtShared *pBt;     /* Sharable content of this btree */
  u8 inTrans;        /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
  u8 sharable;       /* True if we can share pBt with other pSqlite */
  u8 locked;         /* True if pSqlite currently has pBt locked */
  int wantToLock;    /* Number of nested calls to sqlite3BtreeEnter() */
  Btree *pNext;      /* List of Btrees with the same pSqlite value */
  Btree *pPrev;      /* Back pointer of the same list */
};

/*
** Btree.inTrans may take one of the following values.
**
** If the shared-data extension is enabled, there may be multiple users
................................................................................
** sharing the same database file, each connection has it own
** private Btree object for the file and each of those Btrees points
** to this one BtShared object.  BtShared.nRef is the number of
** connections currently sharing this database file.
**
** Fields in this structure are accessed under the BtShared.mutex
** mutex, except for nRef and pNext which are accessed under the
** global SQLITE_MUTEX_STATIC_MASTER mutex.



*/
struct BtShared {
  Pager *pPager;        /* The page cache */
  BtCursor *pCursor;    /* A list of all open cursors */
  MemPage *pPage1;      /* First page of the database */
  u8 inStmt;            /* True if we are in a statement subtransaction */
  u8 readOnly;          /* True if the underlying file is readonly */







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** 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.
**
*************************************************************************
** $Id: btreeInt.h,v 1.12 2007/08/29 00:33:07 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
................................................................................
struct Btree {
  sqlite3 *pSqlite;  /* The database connection holding this btree */
  BtShared *pBt;     /* Sharable content of this btree */
  u8 inTrans;        /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
  u8 sharable;       /* True if we can share pBt with other pSqlite */
  u8 locked;         /* True if pSqlite currently has pBt locked */
  int wantToLock;    /* Number of nested calls to sqlite3BtreeEnter() */
  Btree *pNext;      /* List of other sharable Btrees from the same pSqlite */
  Btree *pPrev;      /* Back pointer of the same list */
};

/*
** Btree.inTrans may take one of the following values.
**
** If the shared-data extension is enabled, there may be multiple users
................................................................................
** sharing the same database file, each connection has it own
** private Btree object for the file and each of those Btrees points
** to this one BtShared object.  BtShared.nRef is the number of
** connections currently sharing this database file.
**
** Fields in this structure are accessed under the BtShared.mutex
** mutex, except for nRef and pNext which are accessed under the
** global SQLITE_MUTEX_STATIC_MASTER mutex.  The pPager field
** may not be modified once it is initially set as long as nRef>0.
** The pSchema field may be set once under BtShared.mutex and
** thereafter is unchanged as long as nRef>0.
*/
struct BtShared {
  Pager *pPager;        /* The page cache */
  BtCursor *pCursor;    /* A list of all open cursors */
  MemPage *pPage1;      /* First page of the database */
  u8 inStmt;            /* True if we are in a statement subtransaction */
  u8 readOnly;          /* True if the underlying file is readonly */

Changes to src/prepare.c.

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**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the implementation of the sqlite3_prepare()
** interface, and routines that contribute to loading the database schema
** from disk.
**
** $Id: prepare.c,v 1.58 2007/08/22 02:56:44 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Fill the InitData structure with an error message that indicates
** that the database is corrupt.
................................................................................
**
*/
int sqlite3InitCallback(void *pInit, int argc, char **argv, char **azColName){
  InitData *pData = (InitData*)pInit;
  sqlite3 *db = pData->db;
  int iDb = pData->iDb;


  pData->rc = SQLITE_OK;
  DbClearProperty(db, iDb, DB_Empty);
  if( db->mallocFailed ){
    corruptSchema(pData, 0);
    return SQLITE_NOMEM;
  }

................................................................................
  ;
#else
  #define temp_master_schema 0
#endif

  assert( iDb>=0 && iDb<db->nDb );
  assert( db->aDb[iDb].pSchema );


  /* zMasterSchema and zInitScript are set to point at the master schema
  ** and initialisation script appropriate for the database being
  ** initialised. zMasterName is the name of the master table.
  */
  if( !OMIT_TEMPDB && iDb==1 ){
    zMasterSchema = temp_master_schema;
................................................................................
  pDb = &db->aDb[iDb];
  if( pDb->pBt==0 ){
    if( !OMIT_TEMPDB && iDb==1 ){
      DbSetProperty(db, 1, DB_SchemaLoaded);
    }
    return SQLITE_OK;
  }

  rc = sqlite3BtreeCursor(pDb->pBt, MASTER_ROOT, 0, 0, 0, &curMain);
  if( rc!=SQLITE_OK && rc!=SQLITE_EMPTY ){
    sqlite3SetString(pzErrMsg, sqlite3ErrStr(rc), (char*)0);

    return rc;
  }

  /* Get the database meta information.
  **
  ** Meta values are as follows:
  **    meta[0]   Schema cookie.  Changes with each schema change.
................................................................................
    int i;
    for(i=0; rc==SQLITE_OK && i<sizeof(meta)/sizeof(meta[0]); i++){
      rc = sqlite3BtreeGetMeta(pDb->pBt, i+1, (u32 *)&meta[i]);
    }
    if( rc ){
      sqlite3SetString(pzErrMsg, sqlite3ErrStr(rc), (char*)0);
      sqlite3BtreeCloseCursor(curMain);

      return rc;
    }
  }else{
    memset(meta, 0, sizeof(meta));
  }
  pDb->pSchema->schema_cookie = meta[0];

................................................................................
      db->pDfltColl = sqlite3FindCollSeq(db, SQLITE_UTF8, "BINARY", 6, 0);
    }else{
      /* If opening an attached database, the encoding much match ENC(db) */
      if( meta[4]!=ENC(db) ){
        sqlite3BtreeCloseCursor(curMain);
        sqlite3SetString(pzErrMsg, "attached databases must use the same"
            " text encoding as main database", (char*)0);

        return SQLITE_ERROR;
      }
    }
  }else{
    DbSetProperty(db, iDb, DB_Empty);
  }
  pDb->pSchema->enc = ENC(db);
................................................................................
  pDb->pSchema->file_format = meta[1];
  if( pDb->pSchema->file_format==0 ){
    pDb->pSchema->file_format = 1;
  }
  if( pDb->pSchema->file_format>SQLITE_MAX_FILE_FORMAT ){
    sqlite3BtreeCloseCursor(curMain);
    sqlite3SetString(pzErrMsg, "unsupported file format", (char*)0);

    return SQLITE_ERROR;
  }


  /* Read the schema information out of the schema tables
  */
  assert( db->init.busy );
................................................................................
    ** of the schema was loaded before the error occured. The primary
    ** purpose of this is to allow access to the sqlite_master table
    ** even when it's contents have been corrupted.
    */
    DbSetProperty(db, iDb, DB_SchemaLoaded);
    rc = SQLITE_OK;
  }

  return rc;
}

/*
** Initialize all database files - the main database file, the file
** used to store temporary tables, and any additional database files
** created using ATTACH statements.  Return a success code.  If an
................................................................................
** bit is set in the flags field of the Db structure. If the database
** file was of zero-length, then the DB_Empty flag is also set.
*/
int sqlite3Init(sqlite3 *db, char **pzErrMsg){
  int i, rc;
  int commit_internal = !(db->flags&SQLITE_InternChanges);
  

  if( db->init.busy ) return SQLITE_OK;
  rc = SQLITE_OK;
  db->init.busy = 1;
  for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
    if( DbHasProperty(db, i, DB_SchemaLoaded) || i==1 ) continue;
    rc = sqlite3InitOne(db, i, pzErrMsg);
    if( rc ){
................................................................................
/*
** This routine is a no-op if the database schema is already initialised.
** Otherwise, the schema is loaded. An error code is returned.
*/
int sqlite3ReadSchema(Parse *pParse){
  int rc = SQLITE_OK;
  sqlite3 *db = pParse->db;

  if( !db->init.busy ){
    rc = sqlite3Init(db, &pParse->zErrMsg);
  }
  if( rc!=SQLITE_OK ){
    pParse->rc = rc;
    pParse->nErr++;
  }
................................................................................
static int schemaIsValid(sqlite3 *db){
  int iDb;
  int rc;
  BtCursor *curTemp;
  int cookie;
  int allOk = 1;


  for(iDb=0; allOk && iDb<db->nDb; iDb++){
    Btree *pBt;
    pBt = db->aDb[iDb].pBt;
    if( pBt==0 ) continue;
    rc = sqlite3BtreeCursor(pBt, MASTER_ROOT, 0, 0, 0, &curTemp);
    if( rc==SQLITE_OK ){
      rc = sqlite3BtreeGetMeta(pBt, 1, (u32 *)&cookie);
................................................................................
  ** function should never be used.
  **
  ** We return -1000000 instead of the more usual -1 simply because using
  ** -1000000 as incorrectly using -1000000 index into db->aDb[] is much 
  ** more likely to cause a segfault than -1 (of course there are assert()
  ** statements too, but it never hurts to play the odds).
  */

  if( pSchema ){
    for(i=0; i<db->nDb; i++){
      if( db->aDb[i].pSchema==pSchema ){
        break;
      }
    }
    assert( i>=0 &&i>=0 &&  i<db->nDb );
................................................................................
  assert( sqlite3_mutex_held(db->mutex) );

  /* If any attached database schemas are locked, do not proceed with
  ** compilation. Instead return SQLITE_LOCKED immediately.
  */
  for(i=0; i<db->nDb; i++) {
    Btree *pBt = db->aDb[i].pBt;


    if( pBt && sqlite3BtreeSchemaLocked(pBt) ){

      const char *zDb = db->aDb[i].zName;
      sqlite3Error(db, SQLITE_LOCKED, "database schema is locked: %s", zDb);
      sqlite3SafetyOff(db);
      return SQLITE_LOCKED;

    }
  }
  
  memset(&sParse, 0, sizeof(sParse));
  sParse.db = db;
  if( nBytes>=0 && zSql[nBytes]!=0 ){
    char *zSqlCopy;
................................................................................
  const char **pzTail       /* OUT: End of parsed string */
){
  int rc;
  if( sqlite3SafetyCheck(db) ){
    return SQLITE_MISUSE;
  }
  sqlite3_mutex_enter(db->mutex);

  rc = sqlite3Prepare(db, zSql, nBytes, saveSqlFlag, ppStmt, pzTail);

  sqlite3_mutex_leave(db->mutex);
  return rc;
}

/*
** Rerun the compilation of a statement after a schema change.
** Return true if the statement was recompiled successfully.
................................................................................
*/
int sqlite3Reprepare(Vdbe *p){
  int rc;
  sqlite3_stmt *pNew;
  const char *zSql;
  sqlite3 *db;


  zSql = sqlite3VdbeGetSql(p);
  if( zSql==0 ){
    return 0;
  }
  db = sqlite3VdbeDb(p);
  assert( sqlite3_mutex_held(db->mutex) );
  rc = sqlite3Prepare(db, zSql, -1, 0, &pNew, 0);
  if( rc ){
    assert( pNew==0 );
    return 0;
  }else{
    assert( pNew!=0 );
  }
  sqlite3VdbeSwap((Vdbe*)pNew, p);
................................................................................

  if( sqlite3SafetyCheck(db) ){
    return SQLITE_MISUSE;
  }
  sqlite3_mutex_enter(db->mutex);
  zSql8 = sqlite3Utf16to8(db, zSql, nBytes);
  if( zSql8 ){
    rc = sqlite3Prepare(db, zSql8, -1, saveSqlFlag, ppStmt, &zTail8);
  }

  if( zTail8 && pzTail ){
    /* If sqlite3_prepare returns a tail pointer, we calculate the
    ** equivalent pointer into the UTF-16 string by counting the unicode
    ** characters between zSql8 and zTail8, and then returning a pointer
    ** the same number of characters into the UTF-16 string.







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**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the implementation of the sqlite3_prepare()
** interface, and routines that contribute to loading the database schema
** from disk.
**
** $Id: prepare.c,v 1.59 2007/08/29 00:33:07 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Fill the InitData structure with an error message that indicates
** that the database is corrupt.
................................................................................
**
*/
int sqlite3InitCallback(void *pInit, int argc, char **argv, char **azColName){
  InitData *pData = (InitData*)pInit;
  sqlite3 *db = pData->db;
  int iDb = pData->iDb;

  assert( sqlite3_mutex_held(db->mutex) );
  pData->rc = SQLITE_OK;
  DbClearProperty(db, iDb, DB_Empty);
  if( db->mallocFailed ){
    corruptSchema(pData, 0);
    return SQLITE_NOMEM;
  }

................................................................................
  ;
#else
  #define temp_master_schema 0
#endif

  assert( iDb>=0 && iDb<db->nDb );
  assert( db->aDb[iDb].pSchema );
  assert( sqlite3_mutex_held(db->mutex) );

  /* zMasterSchema and zInitScript are set to point at the master schema
  ** and initialisation script appropriate for the database being
  ** initialised. zMasterName is the name of the master table.
  */
  if( !OMIT_TEMPDB && iDb==1 ){
    zMasterSchema = temp_master_schema;
................................................................................
  pDb = &db->aDb[iDb];
  if( pDb->pBt==0 ){
    if( !OMIT_TEMPDB && iDb==1 ){
      DbSetProperty(db, 1, DB_SchemaLoaded);
    }
    return SQLITE_OK;
  }
  sqlite3BtreeEnter(pDb->pBt);
  rc = sqlite3BtreeCursor(pDb->pBt, MASTER_ROOT, 0, 0, 0, &curMain);
  if( rc!=SQLITE_OK && rc!=SQLITE_EMPTY ){
    sqlite3SetString(pzErrMsg, sqlite3ErrStr(rc), (char*)0);
    sqlite3BtreeLeave(pDb->pBt);
    return rc;
  }

  /* Get the database meta information.
  **
  ** Meta values are as follows:
  **    meta[0]   Schema cookie.  Changes with each schema change.
................................................................................
    int i;
    for(i=0; rc==SQLITE_OK && i<sizeof(meta)/sizeof(meta[0]); i++){
      rc = sqlite3BtreeGetMeta(pDb->pBt, i+1, (u32 *)&meta[i]);
    }
    if( rc ){
      sqlite3SetString(pzErrMsg, sqlite3ErrStr(rc), (char*)0);
      sqlite3BtreeCloseCursor(curMain);
      sqlite3BtreeLeave(pDb->pBt);
      return rc;
    }
  }else{
    memset(meta, 0, sizeof(meta));
  }
  pDb->pSchema->schema_cookie = meta[0];

................................................................................
      db->pDfltColl = sqlite3FindCollSeq(db, SQLITE_UTF8, "BINARY", 6, 0);
    }else{
      /* If opening an attached database, the encoding much match ENC(db) */
      if( meta[4]!=ENC(db) ){
        sqlite3BtreeCloseCursor(curMain);
        sqlite3SetString(pzErrMsg, "attached databases must use the same"
            " text encoding as main database", (char*)0);
        sqlite3BtreeLeave(pDb->pBt);
        return SQLITE_ERROR;
      }
    }
  }else{
    DbSetProperty(db, iDb, DB_Empty);
  }
  pDb->pSchema->enc = ENC(db);
................................................................................
  pDb->pSchema->file_format = meta[1];
  if( pDb->pSchema->file_format==0 ){
    pDb->pSchema->file_format = 1;
  }
  if( pDb->pSchema->file_format>SQLITE_MAX_FILE_FORMAT ){
    sqlite3BtreeCloseCursor(curMain);
    sqlite3SetString(pzErrMsg, "unsupported file format", (char*)0);
    sqlite3BtreeLeave(pDb->pBt);
    return SQLITE_ERROR;
  }


  /* Read the schema information out of the schema tables
  */
  assert( db->init.busy );
................................................................................
    ** of the schema was loaded before the error occured. The primary
    ** purpose of this is to allow access to the sqlite_master table
    ** even when it's contents have been corrupted.
    */
    DbSetProperty(db, iDb, DB_SchemaLoaded);
    rc = SQLITE_OK;
  }
  sqlite3BtreeLeave(pDb->pBt);
  return rc;
}

/*
** Initialize all database files - the main database file, the file
** used to store temporary tables, and any additional database files
** created using ATTACH statements.  Return a success code.  If an
................................................................................
** bit is set in the flags field of the Db structure. If the database
** file was of zero-length, then the DB_Empty flag is also set.
*/
int sqlite3Init(sqlite3 *db, char **pzErrMsg){
  int i, rc;
  int commit_internal = !(db->flags&SQLITE_InternChanges);
  
  assert( sqlite3_mutex_held(db->mutex) );
  if( db->init.busy ) return SQLITE_OK;
  rc = SQLITE_OK;
  db->init.busy = 1;
  for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
    if( DbHasProperty(db, i, DB_SchemaLoaded) || i==1 ) continue;
    rc = sqlite3InitOne(db, i, pzErrMsg);
    if( rc ){
................................................................................
/*
** This routine is a no-op if the database schema is already initialised.
** Otherwise, the schema is loaded. An error code is returned.
*/
int sqlite3ReadSchema(Parse *pParse){
  int rc = SQLITE_OK;
  sqlite3 *db = pParse->db;
  assert( sqlite3_mutex_held(db->mutex) );
  if( !db->init.busy ){
    rc = sqlite3Init(db, &pParse->zErrMsg);
  }
  if( rc!=SQLITE_OK ){
    pParse->rc = rc;
    pParse->nErr++;
  }
................................................................................
static int schemaIsValid(sqlite3 *db){
  int iDb;
  int rc;
  BtCursor *curTemp;
  int cookie;
  int allOk = 1;

  assert( sqlite3_mutex_held(db->mutex) );
  for(iDb=0; allOk && iDb<db->nDb; iDb++){
    Btree *pBt;
    pBt = db->aDb[iDb].pBt;
    if( pBt==0 ) continue;
    rc = sqlite3BtreeCursor(pBt, MASTER_ROOT, 0, 0, 0, &curTemp);
    if( rc==SQLITE_OK ){
      rc = sqlite3BtreeGetMeta(pBt, 1, (u32 *)&cookie);
................................................................................
  ** function should never be used.
  **
  ** We return -1000000 instead of the more usual -1 simply because using
  ** -1000000 as incorrectly using -1000000 index into db->aDb[] is much 
  ** more likely to cause a segfault than -1 (of course there are assert()
  ** statements too, but it never hurts to play the odds).
  */
  assert( sqlite3_mutex_held(db->mutex) );
  if( pSchema ){
    for(i=0; i<db->nDb; i++){
      if( db->aDb[i].pSchema==pSchema ){
        break;
      }
    }
    assert( i>=0 &&i>=0 &&  i<db->nDb );
................................................................................
  assert( sqlite3_mutex_held(db->mutex) );

  /* If any attached database schemas are locked, do not proceed with
  ** compilation. Instead return SQLITE_LOCKED immediately.
  */
  for(i=0; i<db->nDb; i++) {
    Btree *pBt = db->aDb[i].pBt;
    if( pBt ){
      int rc;
      rc = sqlite3BtreeSchemaLocked(pBt);
      if( rc ){
        const char *zDb = db->aDb[i].zName;
        sqlite3Error(db, SQLITE_LOCKED, "database schema is locked: %s", zDb);
        sqlite3SafetyOff(db);
        return SQLITE_LOCKED;
      }
    }
  }
  
  memset(&sParse, 0, sizeof(sParse));
  sParse.db = db;
  if( nBytes>=0 && zSql[nBytes]!=0 ){
    char *zSqlCopy;
................................................................................
  const char **pzTail       /* OUT: End of parsed string */
){
  int rc;
  if( sqlite3SafetyCheck(db) ){
    return SQLITE_MISUSE;
  }
  sqlite3_mutex_enter(db->mutex);
  sqlite3BtreeEnterAll(db);
  rc = sqlite3Prepare(db, zSql, nBytes, saveSqlFlag, ppStmt, pzTail);
  sqlite3BtreeLeaveAll(db);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

/*
** Rerun the compilation of a statement after a schema change.
** Return true if the statement was recompiled successfully.
................................................................................
*/
int sqlite3Reprepare(Vdbe *p){
  int rc;
  sqlite3_stmt *pNew;
  const char *zSql;
  sqlite3 *db;

  assert( sqlite3_mutex_held(sqlite3VdbeDb(p)->mutex) );
  zSql = sqlite3VdbeGetSql(p);
  if( zSql==0 ){
    return 0;
  }
  db = sqlite3VdbeDb(p);
  assert( sqlite3_mutex_held(db->mutex) );
  rc = sqlite3LockAndPrepare(db, zSql, -1, 0, &pNew, 0);
  if( rc ){
    assert( pNew==0 );
    return 0;
  }else{
    assert( pNew!=0 );
  }
  sqlite3VdbeSwap((Vdbe*)pNew, p);
................................................................................

  if( sqlite3SafetyCheck(db) ){
    return SQLITE_MISUSE;
  }
  sqlite3_mutex_enter(db->mutex);
  zSql8 = sqlite3Utf16to8(db, zSql, nBytes);
  if( zSql8 ){
    rc = sqlite3LockAndPrepare(db, zSql8, -1, saveSqlFlag, ppStmt, &zTail8);
  }

  if( zTail8 && pzTail ){
    /* If sqlite3_prepare returns a tail pointer, we calculate the
    ** equivalent pointer into the UTF-16 string by counting the unicode
    ** characters between zSql8 and zTail8, and then returning a pointer
    ** the same number of characters into the UTF-16 string.