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Overview
Comment:Fix a bug in the WAL checkpoint code causing SQLite to use an inconsistent cache in a subsequent transaction.
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SHA1: d1cadeed4eea20d8892726cc8c69f4f3f57d0cd4
User & Date: dan 2010-04-29 14:51:33
Original Comment: Fix a but in the WAL checkpoint code causing SQLite to use an inconsistent cache in a subsequent transaction.
Context
2010-04-29
14:58
Close all open database connections at the end of wal.test. check-in: 3cc55a75 user: dan tags: wal
14:51
Fix a bug in the WAL checkpoint code causing SQLite to use an inconsistent cache in a subsequent transaction. check-in: d1cadeed user: dan tags: wal
08:47
Add tests to walthread.test. check-in: 9e891e75 user: dan tags: wal
Changes
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Changes to src/wal.c.

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  sqlite3_file *pFd,              /* File descriptor open on db file */
  int sync_flags,                 /* Flags to sync db file with (or 0) */
  u8 *zBuf,                       /* Temporary buffer to use */
  int (*xBusyHandler)(void *),    /* Pointer to busy-handler function */
  void *pBusyHandlerArg           /* Argument to pass to xBusyHandler */
){
  int rc;                         /* Return code */


  assert( !pLog->isLocked );

  /* Wait for an EXCLUSIVE lock on regions B and C. */
  do {
    rc = logLockRegion(pLog, LOG_REGION_B|LOG_REGION_C, LOG_WRLOCK);
  }while( rc==SQLITE_BUSY && xBusyHandler(pBusyHandlerArg) );
................................................................................
  }while( rc==SQLITE_BUSY && xBusyHandler(pBusyHandlerArg) );
  if( rc!=SQLITE_OK ){
    logLockRegion(pLog, LOG_REGION_B|LOG_REGION_C, LOG_UNLOCK);
    return rc;
  }

  /* Copy data from the log to the database file. */
  rc = logSummaryReadHdr(pLog, 0);
  if( rc==SQLITE_OK ){
    rc = logCheckpoint(pLog, pFd, sync_flags, zBuf);
  }










  /* Release the locks. */
  logLockRegion(pLog, LOG_REGION_A|LOG_REGION_B|LOG_REGION_C, LOG_UNLOCK);
  return rc;
}

int sqlite3WalCallback(Log *pLog){







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  sqlite3_file *pFd,              /* File descriptor open on db file */
  int sync_flags,                 /* Flags to sync db file with (or 0) */
  u8 *zBuf,                       /* Temporary buffer to use */
  int (*xBusyHandler)(void *),    /* Pointer to busy-handler function */
  void *pBusyHandlerArg           /* Argument to pass to xBusyHandler */
){
  int rc;                         /* Return code */
  int isChanged = 0;              /* True if a new wal-index header is loaded */

  assert( !pLog->isLocked );

  /* Wait for an EXCLUSIVE lock on regions B and C. */
  do {
    rc = logLockRegion(pLog, LOG_REGION_B|LOG_REGION_C, LOG_WRLOCK);
  }while( rc==SQLITE_BUSY && xBusyHandler(pBusyHandlerArg) );
................................................................................
  }while( rc==SQLITE_BUSY && xBusyHandler(pBusyHandlerArg) );
  if( rc!=SQLITE_OK ){
    logLockRegion(pLog, LOG_REGION_B|LOG_REGION_C, LOG_UNLOCK);
    return rc;
  }

  /* Copy data from the log to the database file. */
  rc = logSummaryReadHdr(pLog, &isChanged);
  if( rc==SQLITE_OK ){
    rc = logCheckpoint(pLog, pFd, sync_flags, zBuf);
  }
  if( isChanged ){
    /* If a new wal-index header was loaded before the checkpoint was 
    ** performed, then the pager-cache associated with log pLog is now
    ** out of date. So zero the cached wal-index header to ensure that
    ** next time the pager opens a snapshot on this database it knows that
    ** the cache needs to be reset.
    */
    memset(&pLog->hdr, 0, sizeof(LogSummaryHdr));
  }

  /* Release the locks. */
  logLockRegion(pLog, LOG_REGION_A|LOG_REGION_B|LOG_REGION_C, LOG_UNLOCK);
  return rc;
}

int sqlite3WalCallback(Log *pLog){

Changes to test/wal.test.

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    } [expr (1<<$ii)]
  }

  catch { db2 close }
  catch { close $::buddy }
  db close
}














































finish_test









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    } [expr (1<<$ii)]
  }

  catch { db2 close }
  catch { close $::buddy }
  db close
}

#-------------------------------------------------------------------------
# Check a fun corruption case has been fixed.
#
# The problem was that after performing a checkpoint using a connection
# that had an out-of-date pager-cache, the next time the connection was
# used it did not realize the cache was out-of-date and proceeded to
# operate with an inconsistent cache. Leading to corruption.
#

catch { db close }
catch { db2 close }
catch { db3 close }
file delete -force test.db test.db-wal
sqlite3 db test.db
sqlite3 db2 test.db

do_test wal-14 {
  execsql {
    PRAGMA journal_mode = WAL;
    CREATE TABLE t1(a PRIMARY KEY, b);
    INSERT INTO t1 VALUES(randomblob(10), randomblob(100));
    INSERT INTO t1 SELECT randomblob(10), randomblob(100) FROM t1;
    INSERT INTO t1 SELECT randomblob(10), randomblob(100) FROM t1;
    INSERT INTO t1 SELECT randomblob(10), randomblob(100) FROM t1;
  }

  db2 eval { 
    INSERT INTO t1 SELECT randomblob(10), randomblob(100);
    INSERT INTO t1 SELECT randomblob(10), randomblob(100);
    INSERT INTO t1 SELECT randomblob(10), randomblob(100);
    INSERT INTO t1 SELECT randomblob(10), randomblob(100);
  }

  # After executing the "PRAGMA checkpoint", connection [db] was being
  # left with an inconsistent cache. Running the CREATE INDEX statement
  # in this state led to database corruption.
  catchsql { 
    PRAGMA checkpoint;
    CREATE INDEX i1 on t1(b);
  }
   
  db2 eval { PRAGMA integrity_check }
} {ok}


finish_test

Changes to test/walthread.test.

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if {[run_thread_tests]==0} { finish_test ; return }

set sqlite_walsummary_mmap_incr 64

# How long, in seconds, to run each test for. If a test is set to run for
# 0 seconds, it is omitted entirely.
#
set seconds(walthread-1)  0
set seconds(walthread-2)  0
set seconds(walthread-3) 20


# The parameter is the name of a variable in the callers context. The
# variable may or may not exist when this command is invoked.
#
# If the variable does exist, its value is returned. Otherwise, this
# command uses [vwait] to wait until it is set, then returns the value.
# In other words, this is a version of the [set VARNAME] command that
................................................................................

    integrity_check
    db close
  }
  set {} "[expr $nRun-$nDel] w, $nDel r"
}

do_thread_test2 walthread-3 -seconds $seconds(walthread-3) -init {
  execsql {
    PRAGMA journal_mode = WAL;
    CREATE TABLE t1(cnt PRIMARY KEY, sum1, sum2);
    CREATE INDEX i1 ON t1(sum1);
    CREATE INDEX i2 ON t1(sum2);
    INSERT INTO t1 VALUES(0, 0, 0);
  }
................................................................................
      error "database content is invalid"
    }
    incr s2 $s1
    incr s1 $c
    incr c 1
  }
}





























finish_test








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if {[run_thread_tests]==0} { finish_test ; return }

set sqlite_walsummary_mmap_incr 64

# How long, in seconds, to run each test for. If a test is set to run for
# 0 seconds, it is omitted entirely.
#
set seconds(walthread-1) 20
set seconds(walthread-2) 20
set seconds(walthread-3) 20
set seconds(walthread-4) 20

# The parameter is the name of a variable in the callers context. The
# variable may or may not exist when this command is invoked.
#
# If the variable does exist, its value is returned. Otherwise, this
# command uses [vwait] to wait until it is set, then returns the value.
# In other words, this is a version of the [set VARNAME] command that
................................................................................

    integrity_check
    db close
  }
  set {} "[expr $nRun-$nDel] w, $nDel r"
}

do_thread_test walthread-3 -seconds $seconds(walthread-3) -init {
  execsql {
    PRAGMA journal_mode = WAL;
    CREATE TABLE t1(cnt PRIMARY KEY, sum1, sum2);
    CREATE INDEX i1 ON t1(sum1);
    CREATE INDEX i2 ON t1(sum2);
    INSERT INTO t1 VALUES(0, 0, 0);
  }
................................................................................
      error "database content is invalid"
    }
    incr s2 $s1
    incr s1 $c
    incr c 1
  }
}

do_thread_test2 walthread-4 -seconds $seconds(walthread-4) -init {
  execsql {
    PRAGMA journal_mode = WAL;
    CREATE TABLE t1(a INTEGER PRIMARY KEY, b UNIQUE);
  }
} -thread r 1 {
  # This connection only ever reads the database. Therefore the 
  # busy-handler is not required. Disable it to check that this is true.
  db busy {}
  while {[tt_continue]} integrity_check
  set {} ok
} -thread w 1 {

  proc wal_hook {zDb nEntry} {
    if {$nEntry>15} { return 1 }
    return 0
  }
  db wal_hook wal_hook
  set row 1
  while {[tt_continue]} {
    db eval { REPLACE INTO t1 VALUES($row, randomblob(300)) }
    incr row
    if {$row == 10} { set row 1 }
  }

  set {} ok
}

finish_test