SQLite

/*
** 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.
**
*************************************************************************
** $Id: btree.c,v 1.461 2008/06/10 17:30:26 danielk1977 Exp $
**
** This file implements a 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"

}
#endif


/*
** Forward declaration
*/
static int checkReadLocks(Btree*, Pgno, BtCursor*, i64);


#ifdef SQLITE_OMIT_SHARED_CACHE
  /*
  ** The functions queryTableLock(), lockTable() and unlockAllTables()
  ** manipulate entries in the BtShared.pLock linked list used to store
  ** shared-cache table level locks. If the library is compiled with the

int sqlite3BtreeRestoreOrClearCursorPosition(BtCursor *pCur){
  int rc;
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState>=CURSOR_REQUIRESEEK );
  if( pCur->eState==CURSOR_FAULT ){
    return pCur->skip;
  }





  pCur->eState = CURSOR_INVALID;
  rc = sqlite3BtreeMoveto(pCur, pCur->pKey, 0, pCur->nKey, 0, &pCur->skip);
  if( rc==SQLITE_OK ){
    sqlite3_free(pCur->pKey);
    pCur->pKey = 0;
    assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_INVALID );
  }

  BtShared *pBt = p->pBt;

  assert( sqlite3BtreeHoldsMutex(p) );
  if( wrFlag ){
    if( pBt->readOnly ){
      return SQLITE_READONLY;
    }
    if( checkReadLocks(p, iTable, 0, 0) ){
      return SQLITE_LOCKED;
    }
  }

  if( pBt->pPage1==0 ){
    rc = lockBtreeWithRetry(p);
    if( rc!=SQLITE_OK ){

**
** 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( cursorHoldsMutex(pCur) );
  rc = restoreOrClearCursorPosition(pCur);
  if( rc==SQLITE_OK ){
    assert( pCur->eState==CURSOR_VALID );
    assert( pCur->pPage!=0 );
    assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );

** This routine checks all cursors that point to table pgnoRoot.
** If any of those cursors were opened with wrFlag==0 in a different
** database connection (a database connection that shares the pager
** cache with the current connection) and that other connection 
** is not in the ReadUncommmitted state, then this routine returns 
** SQLITE_LOCKED.
**

** As well as cursors with wrFlag==0, cursors with wrFlag==1 and 
** isIncrblobHandle==1 are also considered 'read' cursors. Incremental 
** blob cursors are used for both reading and writing.
**
** When pgnoRoot is the root page of an intkey table, this function is also

** responsible for invalidating incremental blob cursors when the table row
** on which they are opened is deleted or modified. Cursors are invalidated
** according to the following rules:
**
**   1) When BtreeClearTable() is called to completely delete the contents
**      of a B-Tree table, pExclude is set to zero and parameter iRow is 
**      set to non-zero. In this case all incremental blob cursors open
**      on the table rooted at pgnoRoot are invalidated.
**
**   2) When BtreeInsert(), BtreeDelete() or BtreePutData() is called to 
**      modify a table row via an SQL statement, pExclude is set to the 
**      write cursor used to do the modification and parameter iRow is set
**      to the integer row id of the B-Tree entry being modified. Unless
**      pExclude is itself an incremental blob cursor, then all incremental
**      blob cursors open on row iRow of the B-Tree are invalidated.
**
**   3) If both pExclude and iRow are set to zero, no incremental blob 
**      cursors are invalidated.
*/
static int checkReadLocks(
  Btree *pBtree, 
  Pgno pgnoRoot, 
  BtCursor *pExclude,
  i64 iRow
){
  BtCursor *p;
  BtShared *pBt = pBtree->pBt;
  sqlite3 *db = pBtree->db;
  assert( sqlite3BtreeHoldsMutex(pBtree) );
  for(p=pBt->pCursor; p; p=p->pNext){
    if( p==pExclude ) continue;

    if( p->pgnoRoot!=pgnoRoot ) continue;
#ifndef SQLITE_OMIT_INCRBLOB
    if( p->isIncrblobHandle && ( 
         (!pExclude && iRow)
      || (pExclude && !pExclude->isIncrblobHandle && p->info.nKey==iRow)
    )){
      p->eState = CURSOR_INVALID;
    }
#endif
    if( p->eState!=CURSOR_VALID ) continue;
    if( p->wrFlag==0 
#ifndef SQLITE_OMIT_INCRBLOB
     || p->isIncrblobHandle
#endif
    ){
      sqlite3 *dbOther = p->pBtree->db;
      if( dbOther==0 ||
         (dbOther!=db && (dbOther->flags & SQLITE_ReadUncommitted)==0) ){
        return SQLITE_LOCKED;
      }


    }
  }
  return SQLITE_OK;
}

/*
** Make sure pBt->pTmpSpace points to an allocation of 

    rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
    return rc;
  }
  assert( !pBt->readOnly );
  if( !pCur->wrFlag ){
    return SQLITE_PERM;   /* Cursor not open for writing */
  }
  if( checkReadLocks(pCur->pBtree, pCur->pgnoRoot, pCur, nKey) ){
    return SQLITE_LOCKED; /* The table pCur points to has a read lock */
  }
  if( pCur->eState==CURSOR_FAULT ){
    return pCur->skip;
  }

  /* Save the positions of any other cursors open on this table */

  }
  if( pCur->idx >= pPage->nCell ){
    return SQLITE_ERROR;  /* The cursor is not pointing to anything */
  }
  if( !pCur->wrFlag ){
    return SQLITE_PERM;   /* Did not open this cursor for writing */
  }
  if( checkReadLocks(pCur->pBtree, pCur->pgnoRoot, pCur, pCur->info.nKey) ){
    return SQLITE_LOCKED; /* The table pCur points to has a read lock */
  }

  /* Restore the current cursor position (a no-op if the cursor is not in 
  ** CURSOR_REQUIRESEEK state) and save the positions of any other cursors 
  ** open on the same table. Then call sqlite3PagerWrite() on the page
  ** that the entry will be deleted from.

int sqlite3BtreeClearTable(Btree *p, int iTable){
  int rc;
  BtShared *pBt = p->pBt;
  sqlite3BtreeEnter(p);
  pBt->db = p->db;
  if( p->inTrans!=TRANS_WRITE ){
    rc = pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
  }else if( (rc = checkReadLocks(p, iTable, 0, 1))!=SQLITE_OK ){
    /* nothing to do */
  }else if( SQLITE_OK!=(rc = saveAllCursors(pBt, iTable, 0)) ){
    /* nothing to do */
  }else{
    rc = clearDatabasePage(pBt, (Pgno)iTable, 0, 0);
  }
  sqlite3BtreeLeave(p);

** Only the data content may only be modified, it is not possible
** to change the length of the data stored.
*/
int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
  assert( cursorHoldsMutex(pCsr) );
  assert( sqlite3_mutex_held(pCsr->pBtree->db->mutex) );
  assert(pCsr->isIncrblobHandle);

  restoreOrClearCursorPosition(pCsr);
  assert( pCsr->eState!=CURSOR_REQUIRESEEK );
  if( pCsr->eState!=CURSOR_VALID ){


    return SQLITE_ABORT;

  }

  /* Check some preconditions: 
  **   (a) the cursor is open for writing,
  **   (b) there is no read-lock on the table being modified and
  **   (c) the cursor points at a valid row of an intKey table.
  */
  if( !pCsr->wrFlag ){
    return SQLITE_READONLY;
  }
  assert( !pCsr->pBt->readOnly 
          && pCsr->pBt->inTransaction==TRANS_WRITE );
  if( checkReadLocks(pCsr->pBtree, pCsr->pgnoRoot, pCsr, 0) ){
    return SQLITE_LOCKED; /* The table pCur points to has a read lock */
  }
  if( pCsr->eState==CURSOR_INVALID || !pCsr->pPage->intKey ){
    return SQLITE_ERROR;
  }

  return accessPayload(pCsr, offset, amt, (unsigned char *)z, 0, 1);

#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# Test that it is possible to have two open blob handles on a single
# blob object.
#
# $Id: incrblob2.test,v 1.2 2008/06/10 17:30:26 danielk1977 Exp $
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl

ifcapable {!autovacuum || !pragma || !incrblob} {
  finish_test
  return
}

do_test incrblob2-1.0 {
  execsql {
    CREATE TABLE blobs(id INTEGER PRIMARY KEY, data BLOB);
    INSERT INTO blobs VALUES(NULL, zeroblob(5000));
    INSERT INTO blobs VALUES(NULL, zeroblob(5000));
    INSERT INTO blobs VALUES(NULL, zeroblob(5000));
    INSERT INTO blobs VALUES(NULL, zeroblob(5000));
  }
} {}

foreach iOffset [list 0 256 4094] {
  do_test incrblob2-1.$iOffset.1 {
    set fd [db incrblob blobs data 1]
    puts $fd "[string repeat x $iOffset]SQLite version 3.6.0"

#--------------------------------------------------------------------------

foreach iOffset [list 0 256 4094] {

  do_test incrblob2-2.$iOffset.1 {
    set fd1 [db incrblob blobs data 1]
    seek $fd1 [expr $iOffset - 5000] end
    fconfigure $fd1 -buffering none

    set fd2 [db incrblob blobs data 1]
    seek $fd2 [expr $iOffset - 5000] end
    fconfigure $fd2 -buffering none

    puts -nonewline $fd1 "123456"
  } {}
  
  do_test incrblob2-2.$iOffset.2 {
    read $fd2 6

do_test incrblob2-3.1 {
  set fd1 [db incrblob blobs data 1]
  fconfigure $fd1 -buffering none
} {}
do_test incrblob2-3.2 {
  execsql {
    INSERT INTO blobs VALUES(5, zeroblob(10240));
  }
} {}
do_test incrblob2-3.3 {
  set rc [catch { read $fd1 6 } msg]
  list $rc $msg
} {0 123456}
do_test incrblob2-3.4 {
  close $fd1
} {}

#--------------------------------------------------------------------------
# The following tests - incrblob2-4.* - test that blob handles are 
# invalidated at the correct times.
#
do_test incrblob2-4.1 {
  db eval BEGIN
  db eval { CREATE TABLE t1(id INTEGER PRIMARY KEY, data BLOB); }
  for {set ii 1} {$ii < 100} {incr ii} {
    set data [string repeat "blob$ii" 500]
    db eval { INSERT INTO t1 VALUES($ii, $data) }
  }
  db eval COMMIT
} {}

proc aborted_handles {} {
  global handles

  set aborted {}
  for {set ii 1} {$ii < 100} {incr ii} {
    set str "blob$ii"
    set nByte [string length $str]
    set iOffset [expr $nByte * $ii * 2]

    set rc [catch {sqlite3_blob_read $handles($ii) $iOffset $nByte} msg]
    if {$rc && $msg eq "SQLITE_ABORT"} {
      lappend aborted $ii
    } else {
      if {$rc || $msg ne $str} {
        error "blob $ii: $msg"
      }
    }
  }
  set aborted
}

do_test incrblob2-4.2 {
  for {set ii 1} {$ii < 100} {incr ii} {
    set handles($ii) [db incrblob t1 data $ii]
  }
  aborted_handles
} {}

# Update row 3. This should abort handle 3 but leave all others untouched.
#
do_test incrblob2-4.3 {
  db eval {UPDATE t1 SET data = data || '' WHERE id = 3}
  aborted_handles
} {3}

# Test that a write to handle 3 also returns SQLITE_ABORT.
#
do_test incrblob2-4.3.1 {
  set rc [catch {sqlite3_blob_write $::handles(3) 10 HELLO} msg]
  list $rc $msg
} {1 SQLITE_ABORT}

# Delete row 14. This should abort handle 6 but leave all others untouched.
#
do_test incrblob2-4.4 {
  db eval {DELETE FROM t1 WHERE id = 14}
  aborted_handles
} {3 14}

# Change the rowid of row 15 to 102. Should abort handle 15.
#
do_test incrblob2-4.5 {
  db eval {UPDATE t1 SET id = 102 WHERE id = 15}
  aborted_handles
} {3 14 15}

# Clobber row 92 using INSERT OR REPLACE.
#
do_test incrblob2-4.6 {
  db eval {INSERT OR REPLACE INTO t1 VALUES(92, zeroblob(1000))}
  aborted_handles
} {3 14 15 92}

# Clobber row 65 using UPDATE OR REPLACE on row 35. This should abort 
# handles 35 and 65.
#
do_test incrblob2-4.7 {
  db eval {UPDATE OR REPLACE t1 SET id = 65 WHERE id = 35}
  aborted_handles
} {3 14 15 35 65 92}

# Insert a couple of new rows. This should not invalidate any handles.
#
do_test incrblob2-4.9 {
  db eval {INSERT INTO t1 SELECT NULL, data FROM t1}
  aborted_handles
} {3 14 15 35 65 92}

# Delete all rows from 1 to 25. This should abort all handles up to 25.
#
do_test incrblob2-4.9 {
  db eval {DELETE FROM t1 WHERE id >=1 AND id <= 25}
  aborted_handles
} {1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 35 65 92}

# Delete the whole table (this will use sqlite3BtreeClearTable()). All handles
# should now be aborted.
#
do_test incrblob2-4.10 {
  db eval {DELETE FROM t1}
  aborted_handles
} {1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99}

do_test incrblob2-4.1.X {
  for {set ii 1} {$ii < 100} {incr ii} {
    close $handles($ii) 
  }
} {}

#--------------------------------------------------------------------------
# The following tests - incrblob2-5.* - test that in shared cache an open
# blob handle counts as a read-lock on its table.
#
ifcapable shared_cache {
  db close
  set ::enable_shared_cache [sqlite3_enable_shared_cache 1]

  do_test incrblob2-5.1 {
    sqlite3 db test.db
    sqlite3 db2 test.db

    execsql {
      INSERT INTO t1 VALUES(1, 'abcde');
    }
  } {}

  do_test incrblob2-5.2 {
    catchsql { INSERT INTO t1 VALUES(2, 'fghij') } db2
  } {0 {}}

  do_test incrblob2-5.3 {
    set blob [db incrblob t1 data 1]
    catchsql { INSERT INTO t1 VALUES(3, 'klmno') } db2
  } {1 {database is locked}}

  do_test incrblob2-5.4 {
    close $blob
    execsql BEGIN db2
    catchsql { INSERT INTO t1 VALUES(4, 'pqrst') } db2
  } {0 {}}

  do_test incrblob2-5.5 {
    set blob [db incrblob -readonly t1 data 1]
    catchsql { INSERT INTO t1 VALUES(5, 'uvwxy') } db2
  } {1 {database table is locked}}

  do_test incrblob2-5.6 {
    close $blob
    catchsql { INSERT INTO t1 VALUES(3, 'klmno') } db2
  } {0 {}}

  db2 close
  db close
  sqlite3_enable_shared_cache $::enable_shared_cache
}

finish_test