SQLite

test:	testfixture$(EXE) sqlite3$(EXE)
	./testfixture$(EXE) $(TOP)/test/veryquick.test

# The next two rules are used to support the "threadtest" target. Building
# threadtest runs a few thread-safety tests that are implemented in C. This
# target is invoked by the releasetest.tcl script.
# 
threadtest3$(EXE): sqlite3.o $(TOP)/test/threadtest3.c $(TOP)/test/tt3_checkpoint.c
	$(TCCX) -O2 sqlite3.o $(TOP)/test/threadtest3.c \
		-o threadtest3$(EXE) $(THREADLIB)

threadtest: threadtest3$(EXE)
	./threadtest3$(EXE)

sqlite3_analyzer$(EXE):	$(TOP)/src/tclsqlite.c sqlite3.c $(TESTSRC) \
			$(TOP)/tool/spaceanal.tcl

#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

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

#ifndef SQLITE_OMIT_WAL
  int sqlite3BtreeCheckpoint(Btree*, int, int *, int *);
#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.
*/

  sqlite3_mutex_leave(db->mutex);
  return pRet;
#else
  return 0;
#endif
}


/*
** Checkpoint database zDb.


*/
int sqlite3_wal_checkpoint_v2(
  sqlite3 *db,                    /* Database handle */
  const char *zDb,                /* Name of attached database (or NULL) */
  int eMode,                      /* SQLITE_CHECKPOINT_* value */
  int *pnLog,                     /* OUT: Size of WAL log in frames */
  int *pnCkpt                     /* OUT: Total number of frames checkpointed */
){
#ifdef SQLITE_OMIT_WAL
  return SQLITE_OK;
#else
  int rc;                         /* Return code */
  int iDb = SQLITE_MAX_ATTACHED;  /* sqlite3.aDb[] index of db to checkpoint */

  if( eMode!=SQLITE_CHECKPOINT_PASSIVE
   && eMode!=SQLITE_CHECKPOINT_FULL
   && eMode!=SQLITE_CHECKPOINT_RESTART
  ){
    return SQLITE_MISUSE;
  }

  sqlite3_mutex_enter(db->mutex);
  if( zDb && zDb[0] ){
    iDb = sqlite3FindDbName(db, zDb);
  }
  if( iDb<0 ){
    rc = SQLITE_ERROR;
    sqlite3Error(db, SQLITE_ERROR, "unknown database: %s", zDb);
  }else{
    rc = sqlite3Checkpoint(db, iDb, eMode, pnLog, pnCkpt);
    sqlite3Error(db, rc, 0);
  }
  rc = sqlite3ApiExit(db, rc);
  sqlite3_mutex_leave(db->mutex);
  return rc;
#endif
}


/*
** Checkpoint database zDb. If zDb is NULL, or if the buffer zDb points
** to contains a zero-length string, all attached databases are 
** checkpointed.
*/
int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb){
  return sqlite3_wal_checkpoint_v2(db, zDb, SQLITE_CHECKPOINT_PASSIVE, 0, 0);
}

#ifndef SQLITE_OMIT_WAL
/*
** Run a checkpoint on database iDb. This is a no-op if database iDb is
** not currently open in WAL mode.
**
** If a transaction is open on the database being checkpointed, this 
** function returns SQLITE_LOCKED and a checkpoint is not attempted. If 
** an error occurs while running the checkpoint, an SQLite error code is 
** returned (i.e. SQLITE_IOERR). Otherwise, SQLITE_OK.
**
** The mutex on database handle db should be held by the caller. The mutex
** associated with the specific b-tree being checkpointed is taken by
** this function while the checkpoint is running.
**
** If iDb is passed SQLITE_MAX_ATTACHED, then all attached databases are
** checkpointed. If an error is encountered it is returned immediately -
** no attempt is made to checkpoint any remaining databases.
**
** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
*/
int sqlite3Checkpoint(sqlite3 *db, int iDb, int eMode, int *pnLog, int *pnCkpt){
  int rc = SQLITE_OK;             /* Return code */
  int i;                          /* Used to iterate through attached dbs */
  int bBusy = 0;                  /* True if SQLITE_BUSY has been encountered */

  assert( sqlite3_mutex_held(db->mutex) );

  for(i=0; i<db->nDb && rc==SQLITE_OK; i++){
    if( i==iDb || iDb==SQLITE_MAX_ATTACHED ){
      rc = sqlite3BtreeCheckpoint(db->aDb[i].pBt, eMode, pnLog, pnCkpt);
      pnLog = 0;
      pnCkpt = 0;
      if( rc==SQLITE_BUSY ){
        bBusy = 1;
        rc = SQLITE_OK;
      }
    }
  }

  return (rc==SQLITE_OK && bBusy) ? SQLITE_BUSY : rc;
}
#endif /* SQLITE_OMIT_WAL */

/*
** This function returns true if main-memory should be used instead of
** a temporary file for transient pager files and statement journals.
** The value returned depends on the value of db->temp_store (runtime

*/
sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){
  return &pPager->pBackup;
}

#ifndef SQLITE_OMIT_WAL
/*
** This function is called when the user invokes "PRAGMA wal_checkpoint",
** "PRAGMA wal_blocking_checkpoint" or calls the sqlite3_wal_checkpoint()
** or wal_blocking_checkpoint() API functions.
**
** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
*/
int sqlite3PagerCheckpoint(Pager *pPager, int eMode, int *pnLog, int *pnCkpt){
  int rc = SQLITE_OK;
  if( pPager->pWal ){

    rc = sqlite3WalCheckpoint(pPager->pWal, eMode,
        pPager->xBusyHandler, pPager->pBusyHandlerArg,
        pPager->ckptSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
        pnLog, pnCkpt
    );
  }
  return rc;
}

int sqlite3PagerWalCallback(Pager *pPager){
  return sqlite3WalCallback(pPager->pWal);
}

int sqlite3PagerSync(Pager *pPager);
int sqlite3PagerCommitPhaseTwo(Pager*);
int sqlite3PagerRollback(Pager*);
int sqlite3PagerOpenSavepoint(Pager *pPager, int n);
int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint);
int sqlite3PagerSharedLock(Pager *pPager);

int sqlite3PagerCheckpoint(Pager *pPager, int, int*, int*);
int sqlite3PagerWalSupported(Pager *pPager);
int sqlite3PagerWalCallback(Pager *pPager);
int sqlite3PagerOpenWal(Pager *pPager, int *pisOpen);
int sqlite3PagerCloseWal(Pager *pPager);

/* Functions used to query pager state and configuration. */
u8 sqlite3PagerIsreadonly(Pager*);

      sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
    }
  }else
#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */

#ifndef SQLITE_OMIT_WAL
  /*
  **   PRAGMA [database.]wal_checkpoint = passive|full|restart
  **
  ** Checkpoint the database.
  */
  if( sqlite3StrICmp(zLeft, "wal_checkpoint")==0 ){
    int iBt = (pId2->z?iDb:SQLITE_MAX_ATTACHED);
    int eMode = SQLITE_CHECKPOINT_PASSIVE;
    if( zRight ){
      if( sqlite3StrICmp(zRight, "full")==0 ){
        eMode = SQLITE_CHECKPOINT_FULL;
      }else if( sqlite3StrICmp(zRight, "restart")==0 ){
        eMode = SQLITE_CHECKPOINT_RESTART;
      }
    }
    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
    sqlite3VdbeSetNumCols(v, 3);
    pParse->nMem = 3;
    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "busy", SQLITE_STATIC);
    sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "log", SQLITE_STATIC);
    sqlite3VdbeSetColName(v, 2, COLNAME_NAME, "checkpointed", SQLITE_STATIC);

    sqlite3VdbeAddOp2(v, OP_Checkpoint, iBt, eMode);
    sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 3);
  }else

  /*
  **   PRAGMA wal_autocheckpoint
  **   PRAGMA wal_autocheckpoint = N
  **
  ** Configure a database connection to automatically checkpoint a database

**
** ^The [wal_checkpoint pragma] can be used to invoke this interface
** from SQL.  ^The [sqlite3_wal_autocheckpoint()] interface and the
** [wal_autocheckpoint pragma] can be used to cause this interface to be
** run whenever the WAL reaches a certain size threshold.
*/
int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb);

/*
**
** CAPI3REF: Checkpoint a database
**
** Run a checkpoint operation on WAL database zDb attached to database 
** handle db. The specific operation is determined by the value of the 
** eMode parameter:
**
** <dl>
** <dt>SQLITE_CHECKPOINT_PASSIVE<dd>
**   Checkpoint as many frames as possible without waiting for any database 
**   readers or writers to finish. Sync the db file if all frames in the log
**   are checkpointed. This mode is the same as calling 
**   sqlite3_wal_checkpoint(). The busy-handler callback is never invoked.
**
** <dt>SQLITE_CHECKPOINT_FULL<dd>
**   This mode blocks (calls the busy-handler callback) until there is no
**   database writer and all readers are reading from the most recent database
**   snapshot. It then checkpoints all frames in the log file and syncs the
**   database file. This call blocks database writers while it is running,
**   but not database readers.
**
** <dt>SQLITE_CHECKPOINT_RESTART<dd>
**   This mode works the same way as SQLITE_CHECKPOINT_FULL, except after 
**   checkpointing the log file it blocks (calls the busy-handler callback)
**   until all readers are reading from the database file only. This ensures 
**   that the next client to write to the database file restarts the log file 
**   from the beginning. This call blocks database writers while it is running,
**   but not database readers.
** </dl>
**
** If pnLog is not NULL, then *pnLog is set to the total number of frames in
** the log file before returning. If pnCkpt is not NULL, then *pnCkpt is set to
** the total number of checkpointed frames (including any that were already
** checkpointed when this function is called). *pnLog and *pnCkpt may be
** populated even if sqlite3_wal_checkpoint_v2() returns other than SQLITE_OK.
** If no values are available because of an error, they are both set to -1
** before returning to communicate this to the caller.
**
** All calls obtain an exclusive "checkpoint" lock on the database file. If
** any other process is running a checkpoint operation at the same time, the 
** lock cannot be obtained and SQLITE_BUSY is returned. Even if there is a 
** busy-handler configured, it will not be invoked in this case.
**
** The SQLITE_CHECKPOINT_FULL and RESTART modes also obtain the exclusive 
** "writer" lock on the database file. If the writer lock cannot be obtained
** immediately, and a busy-handler is configured, it is invoked and the writer
** lock retried until either the busy-handler returns 0 or the lock is
** successfully obtained. The busy-handler is also invoked while waiting for
** database readers as described above. If the busy-handler returns 0 before
** the writer lock is obtained or while waiting for database readers, the
** checkpoint operation proceeds from that point in the same way as 
** SQLITE_CHECKPOINT_PASSIVE - checkpointing as many frames as possible 
** without blocking any further. SQLITE_BUSY is returned in this case.
**
** If parameter zDb is NULL or points to a zero length string, then the
** specified operation is attempted on all WAL databases. In this case the
** values written to output parameters *pnLog and *pnCkpt are undefined. If 
** an SQLITE_BUSY error is encountered when processing one or more of the 
** attached WAL databases, the operation is still attempted on any remaining 
** attached databases and SQLITE_BUSY is returned to the caller. If any other 
** error occurs while processing an attached database, processing is abandoned 
** and the error code returned to the caller immediately. If no error 
** (SQLITE_BUSY or otherwise) is encountered while processing the attached 
** databases, SQLITE_OK is returned.
**
** If database zDb is the name of an attached database that is not in WAL
** mode, SQLITE_OK is returned and both *pnLog and *pnCkpt set to -1. If
** zDb is not NULL (or a zero length string) and is not the name of any
** attached database, SQLITE_ERROR is returned to the caller.
*/
int sqlite3_wal_checkpoint_v2(
  sqlite3 *db,                    /* Database handle */
  const char *zDb,                /* Name of attached database (or NULL) */
  int eMode,                      /* SQLITE_CHECKPOINT_* value */
  int *pnLog,                     /* OUT: Size of WAL log in frames */
  int *pnCkpt                     /* OUT: Total number of frames checkpointed */
);
#define SQLITE_CHECKPOINT_PASSIVE 0
#define SQLITE_CHECKPOINT_FULL    1
#define SQLITE_CHECKPOINT_RESTART 2


/*
** Undo the hack that converts floating point types to integer for
** builds on processors without floating point support.
*/
#ifdef SQLITE_OMIT_FLOATING_POINT
# undef double

int sqlite3TransferBindings(sqlite3_stmt *, sqlite3_stmt *);
int sqlite3Reprepare(Vdbe*);
void sqlite3ExprListCheckLength(Parse*, ExprList*, const char*);
CollSeq *sqlite3BinaryCompareCollSeq(Parse *, Expr *, Expr *);
int sqlite3TempInMemory(const sqlite3*);
VTable *sqlite3GetVTable(sqlite3*, Table*);
const char *sqlite3JournalModename(int);
int sqlite3Checkpoint(sqlite3*, int, int, int*, int*);
int sqlite3WalDefaultHook(void*,sqlite3*,const char*,int);

/* Declarations for functions in fkey.c. All of these are replaced by
** no-op macros if OMIT_FOREIGN_KEY is defined. In this case no foreign
** key functionality is available. If OMIT_TRIGGER is defined but
** OMIT_FOREIGN_KEY is not, only some of the functions are no-oped. In
** this case foreign keys are parsed, but no other functionality is 

  if( sqlite3VdbeMemTooBig(pMem) ){
    goto too_big;
  }
  break;
}

#ifndef SQLITE_OMIT_WAL
/* Opcode: Checkpoint P1 P2 P3 * *
**
** Checkpoint database P1. This is a no-op if P1 is not currently in
** WAL mode. Parameter P2 is one of SQLITE_CHECKPOINT_PASSIVE, FULL
** or RESTART.
*/
case OP_Checkpoint: {
  int nLog = -1;                  /* Number of pages in WAL log */
  int nCkpt = -1;                 /* Number of checkpointed pages */
  int bBusy = 0;
  assert( pOp->p2==SQLITE_CHECKPOINT_PASSIVE
       || pOp->p2==SQLITE_CHECKPOINT_FULL
       || pOp->p2==SQLITE_CHECKPOINT_RESTART
  );
  rc = sqlite3Checkpoint(db, pOp->p1, pOp->p2, &nLog, &nCkpt);
  if( rc==SQLITE_BUSY ){
    rc = SQLITE_OK;
    bBusy = 1;
  }

  aMem[1].u.i = bBusy;
  aMem[2].u.i = nLog;
  aMem[3].u.i = nCkpt;
  MemSetTypeFlag(&aMem[1], MEM_Int);
  MemSetTypeFlag(&aMem[2], MEM_Int);
  MemSetTypeFlag(&aMem[3], MEM_Int);

  break;
};  
#endif

#ifndef SQLITE_OMIT_PRAGMA
/* Opcode: JournalMode P1 P2 P3 * P5
**

  if( rc!=SQLITE_OK ){
    walIteratorFree(p);
  }
  *pp = p;
  return rc;
}

/*
** Attempt to obtain the exclusive WAL lock defined by parameters lockIdx and
** n. If the attempt fails and parameter xBusy is not NULL, then it is a
** busy-handler function. Invoke it and retry the lock until either the
** lock is successfully obtained or the busy-handler returns 0.
*/
static int walBusyLock(
  Wal *pWal,                      /* WAL connection */
  int (*xBusy)(void*),            /* Function to call when busy */
  void *pBusyArg,                 /* Context argument for xBusyHandler */
  int lockIdx,                    /* Offset of first byte to lock */
  int n                           /* Number of bytes to lock */
){
  int rc;
  do {
    rc = walLockExclusive(pWal, lockIdx, n);
  }while( xBusy && rc==SQLITE_BUSY && xBusy(pBusyArg) );
  return rc;
}

/*
** The cache of the wal-index header must be valid to call this function.
** Return the page-size in bytes used by the database.
*/
static int walPagesize(Wal *pWal){
  return (pWal->hdr.szPage&0xfe00) + ((pWal->hdr.szPage&0x0001)<<16);
}

/*
** Copy as much content as we can from the WAL back into the database file
** in response to an sqlite3_wal_checkpoint() request or the equivalent.
**
** The amount of information copies from WAL to database might be limited
** by active readers.  This routine will never overwrite a database page

**
** The caller must be holding sufficient locks to ensure that no other
** checkpoint is running (in any other thread or process) at the same
** time.
*/
static int walCheckpoint(
  Wal *pWal,                      /* Wal connection */
  int eMode,                      /* One of PASSIVE, FULL or RESTART */
  int (*xBusyCall)(void*),        /* Function to call when busy */
  void *pBusyArg,                 /* Context argument for xBusyHandler */
  int sync_flags,                 /* Flags for OsSync() (or 0) */
  u8 *zBuf,                       /* Temporary buffer to use */

  int *pnCkpt                     /* Total frames checkpointed */
){
  int rc;                         /* Return code */
  int szPage;                     /* Database page-size */
  WalIterator *pIter = 0;         /* Wal iterator context */
  u32 iDbpage = 0;                /* Next database page to write */
  u32 iFrame = 0;                 /* Wal frame containing data for iDbpage */
  u32 mxSafeFrame;                /* Max frame that can be backfilled */
  u32 mxPage;                     /* Max database page to write */
  int i;                          /* Loop counter */
  volatile WalCkptInfo *pInfo;    /* The checkpoint status information */
  int (*xBusy)(void*) = 0;        /* Function to call when waiting for locks */

  szPage = walPagesize(pWal);
  testcase( szPage<=32768 );
  testcase( szPage>=65536 );


  /* Allocate the iterator */
  rc = walIteratorInit(pWal, &pIter);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  assert( pIter );

  pInfo = walCkptInfo(pWal);
  mxPage = pWal->hdr.nPage;
  if( pnCkpt ) *pnCkpt = pInfo->nBackfill;
  if( eMode!=SQLITE_CHECKPOINT_PASSIVE ) xBusy = xBusyCall;



  /* Compute in mxSafeFrame the index of the last frame of the WAL that is
  ** safe to write into the database.  Frames beyond mxSafeFrame might
  ** overwrite database pages that are in use by active readers and thus
  ** cannot be backfilled from the WAL.
  */
  mxSafeFrame = pWal->hdr.mxFrame;


  for(i=1; i<WAL_NREADER; i++){
    u32 y = pInfo->aReadMark[i];
    if( mxSafeFrame>y ){
      assert( y<=pWal->hdr.mxFrame );
      rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(i), 1);
      if( rc==SQLITE_OK ){
        pInfo->aReadMark[i] = READMARK_NOT_USED;
        walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
      }else if( rc==SQLITE_BUSY ){
        mxSafeFrame = y;
        xBusy = 0;
      }else{
        goto walcheckpoint_out;
      }
    }
  }

  if( pInfo->nBackfill<mxSafeFrame
   && (rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(0), 1))==SQLITE_OK
  ){
    i64 nSize;                    /* Current size of database file */
    u32 nBackfill = pInfo->nBackfill;

    /* Sync the WAL to disk */
    if( sync_flags ){
      rc = sqlite3OsSync(pWal->pWalFd, sync_flags);

        rc = sqlite3OsTruncate(pWal->pDbFd, szDb);
        if( rc==SQLITE_OK && sync_flags ){
          rc = sqlite3OsSync(pWal->pDbFd, sync_flags);
        }
      }
      if( rc==SQLITE_OK ){
        pInfo->nBackfill = mxSafeFrame;
        if( pnCkpt ) *pnCkpt = mxSafeFrame;
      }
    }

    /* Release the reader lock held while backfilling */
    walUnlockExclusive(pWal, WAL_READ_LOCK(0), 1);
  }

  if( rc==SQLITE_BUSY ){
    /* Reset the return code so as not to report a checkpoint failure
    ** just because there are active readers.  */
    rc = SQLITE_OK;
  }

  /* If this is an SQLITE_CHECKPOINT_RESTART operation, and the entire wal
  ** file has been copied into the database file, then block until all
  ** readers have finished using the wal file. This ensures that the next
  ** process to write to the database restarts the wal file.
  */
  if( rc==SQLITE_OK && eMode!=SQLITE_CHECKPOINT_PASSIVE ){
    assert( pWal->writeLock );
    if( pInfo->nBackfill<pWal->hdr.mxFrame ){
      rc = SQLITE_BUSY;
    }else if( eMode==SQLITE_CHECKPOINT_RESTART ){
      assert( mxSafeFrame==pWal->hdr.mxFrame );
      rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(1), WAL_NREADER-1);
      if( rc==SQLITE_OK ){
        walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
      }
    }
  }

 walcheckpoint_out:
  walIteratorFree(pIter);
  return rc;
}

/*

    ** The EXCLUSIVE lock is not released before returning.
    */
    rc = sqlite3OsLock(pWal->pDbFd, SQLITE_LOCK_EXCLUSIVE);
    if( rc==SQLITE_OK ){
      if( pWal->exclusiveMode==WAL_NORMAL_MODE ){
        pWal->exclusiveMode = WAL_EXCLUSIVE_MODE;
      }
      rc = sqlite3WalCheckpoint(
          pWal, SQLITE_CHECKPOINT_PASSIVE, 0, 0, sync_flags, nBuf, zBuf, 0, 0
      );
      if( rc==SQLITE_OK ){
        isDelete = 1;
      }
    }

    walIndexClose(pWal, isDelete);
    sqlite3OsClose(pWal->pWalFd);

/* 
** This routine is called to implement sqlite3_wal_checkpoint() and
** related interfaces.
**
** Obtain a CHECKPOINT lock and then backfill as much information as
** we can from WAL into the database.
**
** If parameter xBusy is not NULL, it is a pointer to a busy-handler
** callback. In this case this function runs a blocking checkpoint.
*/
int sqlite3WalCheckpoint(
  Wal *pWal,                      /* Wal connection */
  int eMode,                      /* PASSIVE, FULL or RESTART */
  int (*xBusy)(void*),            /* Function to call when busy */
  void *pBusyArg,                 /* Context argument for xBusyHandler */
  int sync_flags,                 /* Flags to sync db file with (or 0) */
  int nBuf,                       /* Size of temporary buffer */
  u8 *zBuf,                       /* Temporary buffer to use */
  int *pnLog,                     /* OUT: Number of frames in WAL */
  int *pnCkpt                     /* OUT: Number of backfilled frames in WAL */
){
  int rc;                         /* Return code */
  int isChanged = 0;              /* True if a new wal-index header is loaded */
  int eMode2 = eMode;             /* Mode to pass to walCheckpoint() */

  assert( pWal->ckptLock==0 );
  assert( pWal->writeLock==0 );

  WALTRACE(("WAL%p: checkpoint begins\n", pWal));
  rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1);
  if( rc ){
    /* Usually this is SQLITE_BUSY meaning that another thread or process
    ** is already running a checkpoint, or maybe a recovery.  But it might
    ** also be SQLITE_IOERR. */
    return rc;
  }
  pWal->ckptLock = 1;

  /* If this is a blocking-checkpoint, then obtain the write-lock as well
  ** to prevent any writers from running while the checkpoint is underway.
  ** This has to be done before the call to walIndexReadHdr() below.
  **
  ** If the writer lock cannot be obtained, then a passive checkpoint is
  ** run instead. Since the checkpointer is not holding the writer lock,
  ** there is no point in blocking waiting for any readers. Assuming no 
  ** other error occurs, this function will return SQLITE_BUSY to the caller.
  */
  if( eMode!=SQLITE_CHECKPOINT_PASSIVE ){
    rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_WRITE_LOCK, 1);
    if( rc==SQLITE_OK ){
      pWal->writeLock = 1;
    }else if( rc==SQLITE_BUSY ){
      eMode2 = SQLITE_CHECKPOINT_PASSIVE;
      rc = SQLITE_OK;
    }
  }

  /* Read the wal-index header. */
  if( rc==SQLITE_OK ){
    rc = walIndexReadHdr(pWal, &isChanged);
  }

  /* Copy data from the log to the database file. */
  if( rc==SQLITE_OK && pWal->hdr.mxFrame ){
    if( walPagesize(pWal)!=nBuf ){
      rc = SQLITE_CORRUPT_BKPT;
    }else{
      if( pnLog ) *pnLog = (int)pWal->hdr.mxFrame;
      rc = walCheckpoint(pWal, eMode2, xBusy, pBusyArg, sync_flags,zBuf,pnCkpt);
    }
  }

  if( isChanged ){
    /* If a new wal-index header was loaded before the checkpoint was 
    ** performed, then the pager-cache associated with pWal 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(&pWal->hdr, 0, sizeof(WalIndexHdr));
  }

  /* Release the locks. */
  sqlite3WalEndWriteTransaction(pWal);
  walUnlockExclusive(pWal, WAL_CKPT_LOCK, 1);
  pWal->ckptLock = 0;
  WALTRACE(("WAL%p: checkpoint %s\n", pWal, rc ? "failed" : "ok"));
  return (rc==SQLITE_OK && eMode!=eMode2 ? SQLITE_BUSY : rc);
}

/* Return the value to pass to a sqlite3_wal_hook callback, the
** number of frames in the WAL at the point of the last commit since
** sqlite3WalCallback() was called.  If no commits have occurred since
** the last call, then return 0.
*/

#ifndef _WAL_H_
#define _WAL_H_

#include "sqliteInt.h"

#ifdef SQLITE_OMIT_WAL
# define sqlite3WalOpen(x,y,z)                   0
# define sqlite3WalClose(w,x,y,z)                0
# define sqlite3WalBeginReadTransaction(y,z)     0
# define sqlite3WalEndReadTransaction(z)
# define sqlite3WalRead(v,w,x,y,z)               0
# define sqlite3WalDbsize(y)                     0
# define sqlite3WalBeginWriteTransaction(y)      0
# define sqlite3WalEndWriteTransaction(x)        0
# define sqlite3WalUndo(x,y,z)                   0
# define sqlite3WalSavepoint(y,z)
# define sqlite3WalSavepointUndo(y,z)            0
# define sqlite3WalFrames(u,v,w,x,y,z)           0
# define sqlite3WalCheckpoint(r,s,t,u,v,w,x,y,z) 0
# define sqlite3WalCallback(z)                   0
# define sqlite3WalExclusiveMode(y,z)            0
# define sqlite3WalHeapMemory(z)                 0
#else

#define WAL_SAVEPOINT_NDATA 4

/* Connection to a write-ahead log (WAL) file. 
** There is one object of this type for each pager. 
*/

/* Write a frame or frames to the log. */
int sqlite3WalFrames(Wal *pWal, int, PgHdr *, Pgno, int, int);

/* Copy pages from the log to the database file */ 
int sqlite3WalCheckpoint(
  Wal *pWal,                      /* Write-ahead log connection */
  int eMode,                      /* One of PASSIVE, FULL and RESTART */
  int (*xBusy)(void*),            /* Function to call when busy */
  void *pBusyArg,                 /* Context argument for xBusyHandler */
  int sync_flags,                 /* Flags to sync db file with (or 0) */
  int nBuf,                       /* Size of buffer nBuf */
  u8 *zBuf,                       /* Temporary buffer to use */
  int *pnLog,                     /* OUT: Number of frames in WAL */
  int *pnCkpt                     /* OUT: Number of backfilled frames in WAL */
);

/* Return the value to pass to a sqlite3_wal_hook callback, the
** number of frames in the WAL at the point of the last commit since
** sqlite3WalCallback() was called.  If no commits have occurred since
** the last call, then return 0.
*/

  }
} {noname inmem}
do_test attach-10.2 {
  lrange [execsql {
    PRAGMA database_list;
  }] 9 end
} {4 noname {} 5 inmem {}}

finish_test

do_test pager1-22.1.1 {
  faultsim_delete_and_reopen
  execsql {
    CREATE TABLE ko(c DEFAULT 'abc', b DEFAULT 'def');
    INSERT INTO ko DEFAULT VALUES;
  }
  execsql { PRAGMA wal_checkpoint }
} {0 -1 -1}
do_test pager1-22.2.1 {
  testvfs tv -default 1
  tv filter xSync
  tv script xSyncCb
  proc xSyncCb {args} {incr ::synccount}
  set ::synccount 0
  sqlite3 db test.db

  launch_thread(&err, &threads, dynamic_triggers_1, 0);

  join_all_threads(&err, &threads);

  print_and_free_err(&err);
}

#include "tt3_checkpoint.c"

int main(int argc, char **argv){
  struct ThreadTest {
    void (*xTest)(int);
    const char *zTest;
    int nMs;
  } aTest[] = {
    { walthread1, "walthread1", 20000 },
    { walthread2, "walthread2", 20000 },
    { walthread3, "walthread3", 20000 },
    { walthread4, "walthread4", 20000 },
    { walthread5, "walthread5",  1000 },
    { walthread5, "walthread5",  1000 },
    
    { cgt_pager_1,      "cgt_pager_1", 0 },
    { dynamic_triggers, "dynamic_triggers", 20000 },

    { checkpoint_starvation_1, "checkpoint_starvation_1", 10000 },
    { checkpoint_starvation_2, "checkpoint_starvation_2", 10000 },
  };

  int i;
  char *zTest = 0;
  int nTest = 0;
  int bTestfound = 0;
  int bPrefix = 0;

/*
** 2001 September 15
**
** 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 is part of the test program "threadtest3". Despite being a C
** file it is not compiled separately, but included by threadtest3.c using
** the #include directive normally used with header files.
**
** This file contains the implementation of test cases:
**
**     checkpoint_starvation_1
**     checkpoint_starvation_2
*/

/*
** Both test cases involve 1 writer/checkpointer thread and N reader threads.
** 
** Each reader thread performs a series of read transactions, one after 
** another. Each read transaction lasts for 100 ms.
**
** The writer writes transactions as fast as possible. It uses a callback
** registered with sqlite3_wal_hook() to try to keep the WAL-size limited to 
** around 50 pages.
**
** In test case checkpoint_starvation_1, the auto-checkpoint uses 
** SQLITE_CHECKPOINT_PASSIVE. In checkpoint_starvation_2, it uses RESTART.
** The expectation is that in the first case the WAL file will grow very 
** large, and in the second will be limited to the 50 pages or thereabouts.
** However, the overall transaction throughput will be lower for 
** checkpoint_starvation_2, as every checkpoint will block for up to 200 ms
** waiting for readers to clear.
*/

/* Frame limit used by the WAL hook for these tests. */
#define CHECKPOINT_STARVATION_FRAMELIMIT 50

/* Duration in ms of each read transaction */
#define CHECKPOINT_STARVATION_READMS    100

struct CheckpointStarvationCtx {
  int eMode;
  int nMaxFrame;
};
typedef struct CheckpointStarvationCtx CheckpointStarvationCtx;

static int checkpoint_starvation_walhook(
  void *pCtx, 
  sqlite3 *db, 
  const char *zDb, 
  int nFrame
){
  CheckpointStarvationCtx *p = (CheckpointStarvationCtx *)pCtx;
  if( nFrame>p->nMaxFrame ){
    p->nMaxFrame = nFrame;
  }
  if( nFrame>=CHECKPOINT_STARVATION_FRAMELIMIT ){
    sqlite3_wal_checkpoint_v2(db, zDb, p->eMode, 0, 0);
  }
  return SQLITE_OK;
}

static char *checkpoint_starvation_reader(int iTid, int iArg){
  Error err = {0};
  Sqlite db = {0};

  opendb(&err, &db, "test.db", 0);
  while( !timetostop(&err) ){
    i64 iCount1, iCount2;
    sql_script(&err, &db, "BEGIN");
    iCount1 = execsql_i64(&err, &db, "SELECT count(x) FROM t1");
    usleep(CHECKPOINT_STARVATION_READMS*1000);
    iCount2 = execsql_i64(&err, &db, "SELECT count(x) FROM t1");
    sql_script(&err, &db, "COMMIT");

    if( iCount1!=iCount2 ){
      test_error(&err, "Isolation failure - %lld %lld", iCount1, iCount2);
    }
  }
  closedb(&err, &db);

  print_and_free_err(&err);
  return 0;
}

static void checkpoint_starvation_main(int nMs, CheckpointStarvationCtx *p){
  Error err = {0};
  Sqlite db = {0};
  Threadset threads = {0};
  int nInsert = 0;
  int i;

  opendb(&err, &db, "test.db", 1);
  sql_script(&err, &db, 
      "PRAGMA page_size = 1024;"
      "PRAGMA journal_mode = WAL;"
      "CREATE TABLE t1(x);"
  );

  setstoptime(&err, nMs);

  for(i=0; i<4; i++){
    launch_thread(&err, &threads, checkpoint_starvation_reader, 0);
    usleep(CHECKPOINT_STARVATION_READMS*1000/4);
  }

  sqlite3_wal_hook(db.db, checkpoint_starvation_walhook, (void *)p);
  while( !timetostop(&err) ){
    sql_script(&err, &db, "INSERT INTO t1 VALUES(randomblob(1200))");
    nInsert++;
  }

  printf(" Checkpoint mode  : %s\n",
      p->eMode==SQLITE_CHECKPOINT_PASSIVE ? "PASSIVE" : "RESTART"
  );
  printf(" Peak WAL         : %d frames\n", p->nMaxFrame);
  printf(" Transaction count: %d transactions\n", nInsert);

  join_all_threads(&err, &threads);
  closedb(&err, &db);
  print_and_free_err(&err);
}

static void checkpoint_starvation_1(int nMs){
  Error err = {0};
  CheckpointStarvationCtx ctx = { SQLITE_CHECKPOINT_PASSIVE, 0 };
  checkpoint_starvation_main(nMs, &ctx);
  if( ctx.nMaxFrame<(CHECKPOINT_STARVATION_FRAMELIMIT*10) ){
    test_error(&err, "WAL failed to grow - %d frames", ctx.nMaxFrame);
  }
  print_and_free_err(&err);
}

static void checkpoint_starvation_2(int nMs){
  Error err = {0};
  CheckpointStarvationCtx ctx = { SQLITE_CHECKPOINT_RESTART, 0 };
  checkpoint_starvation_main(nMs, &ctx);
  if( ctx.nMaxFrame>CHECKPOINT_STARVATION_FRAMELIMIT+10 ){
    test_error(&err, "WAL grew too large - %d frames", ctx.nMaxFrame);
  }
  print_and_free_err(&err);
}

    PRAGMA wal_checkpoint;
    BEGIN;
      INSERT INTO t2 VALUES('w', 'x');
      SAVEPOINT save;
        INSERT INTO t2 VALUES('y', 'z');
      ROLLBACK TO save;
    COMMIT;

  }
  execsql { SELECT * FROM t2 }
} {w x}


reopen_db
do_test wal-5.1 {
  execsql {
    CREATE TEMP TABLE t2(a, b);

  # checkpointing the database. But not from writing to it.
  #
  do_test wal-10.$tn.11 {
    sql2 { BEGIN; SELECT * FROM t1 }
  } {1 2 3 4 5 6 7 8 9 10}
  do_test wal-10.$tn.12 {
    catchsql { PRAGMA wal_checkpoint } 
  } {0 {0 13 13}}   ;# Reader no longer block checkpoints
  do_test wal-10.$tn.13 {
    execsql { INSERT INTO t1 VALUES(11, 12) }
    sql2 {SELECT * FROM t1}
  } {1 2 3 4 5 6 7 8 9 10}

  # Writers do not block checkpoints any more either.
  #
  do_test wal-10.$tn.14 {
    catchsql { PRAGMA wal_checkpoint } 
  } {0 {0 15 13}}

  # The following series of test cases used to verify another blocking
  # case in WAL - a case which no longer blocks.
  #
  do_test wal-10.$tn.15 {
    sql2 { COMMIT; BEGIN; SELECT * FROM t1; }
  } {1 2 3 4 5 6 7 8 9 10 11 12}
  do_test wal-10.$tn.16 {
    catchsql { PRAGMA wal_checkpoint } 
  } {0 {0 15 15}}
  do_test wal-10.$tn.17 {
    execsql { PRAGMA wal_checkpoint } 
  } {0 15 15}
  do_test wal-10.$tn.18 {
    sql3 { BEGIN; SELECT * FROM t1 }
  } {1 2 3 4 5 6 7 8 9 10 11 12}
  do_test wal-10.$tn.19 {
    catchsql { INSERT INTO t1 VALUES(13, 14) }
  } {0 {}}
  do_test wal-10.$tn.20 {

  } {1 2 3 4 5 6 7 8 9 10 11 12 13 14}

  # Another series of tests that used to demonstrate blocking behavior
  # but which now work.
  #
  do_test wal-10.$tn.23 {
    execsql { PRAGMA wal_checkpoint }
  } {0 17 17}
  do_test wal-10.$tn.24 {
    sql2 { BEGIN; SELECT * FROM t1; }
  } {1 2 3 4 5 6 7 8 9 10 11 12 13 14}
  do_test wal-10.$tn.25 {
    execsql { PRAGMA wal_checkpoint }
  } {0 17 17}
  do_test wal-10.$tn.26 {
    catchsql { INSERT INTO t1 VALUES(15, 16) }
  } {0 {}}
  do_test wal-10.$tn.27 {
    sql3 { INSERT INTO t1 VALUES(17, 18) }
  } {}
  do_test wal-10.$tn.28 {
    code3 {
      set ::STMT [sqlite3_prepare db3 "SELECT * FROM t1" -1 TAIL]
      sqlite3_step $::STMT
    }
    execsql { SELECT * FROM t1 }
  } {1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18}
  do_test wal-10.$tn.29 {
    execsql { INSERT INTO t1 VALUES(19, 20) }
    catchsql { PRAGMA wal_checkpoint }
  } {0 {0 6 0}}
  do_test wal-10.$tn.30 {
    code3 { sqlite3_finalize $::STMT }
    execsql { PRAGMA wal_checkpoint }
  } {0 6 0}

  # At one point, if a reader failed to upgrade to a writer because it
  # was reading an old snapshot, the write-locks were not being released.
  # Test that this bug has been fixed.
  #
  do_test wal-10.$tn.31 {
    sql2 COMMIT

    sql2 {
      BEGIN;
        SELECT * FROM t1;
    }
  } {a b c d}
  do_test wal-10.$tn.36 {
    catchsql { PRAGMA wal_checkpoint }
  } {0 {0 16 16}}
  do_test wal-10.$tn.36 {
    sql3 { INSERT INTO t1 VALUES('e', 'f') }
    sql2 { SELECT * FROM t1 }
  } {a b c d}
  do_test wal-10.$tn.37 {
    sql2 COMMIT
    execsql { PRAGMA wal_checkpoint }
  } {0 18 18}
}

#-------------------------------------------------------------------------
# This block of tests, wal-11.*, test that nothing goes terribly wrong
# if frames must be written to the log file before a transaction is
# committed (in order to free up memory).
#

  execsql {
    PRAGMA wal_checkpoint;
    UPDATE t2 SET y = 2 WHERE x = 'B'; 
    PRAGMA wal_checkpoint;
    UPDATE t1 SET y = 1 WHERE x = 'A';
    PRAGMA wal_checkpoint;
    UPDATE t1 SET y = 0 WHERE x = 'A';

  }
  execsql {  SELECT * FROM t2 }
} {B 2}
do_test wal-12.6 {
  file copy -force test.db test2.db
  file copy -force test.db-wal test2.db-wal
  sqlite3_wal db2 test2.db
  execsql { SELECT * FROM t2 } db2
} {B 2}

  set fd [open test.db-wal w]
  seek $fd [expr 200*1024*1024]
  puts $fd ""
  close $fd
  sqlite3 db test.db
  execsql { SELECT * FROM t2 }
} {B 2}
breakpoint
do_test wal-13.1.3 {
  db close
  file exists test.db-wal
} {0}

do_test wal-13.2.1 {
  sqlite3 db test.db

# The following block of tests - wal-16.* - test that if a NULL pointer or
# an empty string is passed as the second argument of the wal_checkpoint()
# API, an attempt is made to checkpoint all attached databases.
#
foreach {tn ckpt_cmd ckpt_res ckpt_main ckpt_aux} {
  1 {sqlite3_wal_checkpoint db}              SQLITE_OK     1 1
  2 {sqlite3_wal_checkpoint db ""}           SQLITE_OK     1 1
  3 {db eval "PRAGMA wal_checkpoint"}        {0 10 10}     1 1

  4 {sqlite3_wal_checkpoint db main}         SQLITE_OK     1 0
  5 {sqlite3_wal_checkpoint db aux}          SQLITE_OK     0 1
  6 {sqlite3_wal_checkpoint db temp}         SQLITE_OK     0 0
  7 {db eval "PRAGMA main.wal_checkpoint"}   {0 10 10}     1 0
  8 {db eval "PRAGMA aux.wal_checkpoint"}    {0 16 16}     0 1
  9 {db eval "PRAGMA temp.wal_checkpoint"}   {0 -1 -1}     0 0
} {
  do_test wal-16.$tn.1 {
    file delete -force test2.db test2.db-wal test2.db-journal
    file delete -force test.db test.db-wal test.db-journal

    sqlite3 db test.db
    execsql {

      INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 8192 */
      INSERT INTO t1 SELECT randomblob(900) FROM t1;       /* 16384 */
    } }
  }
} {0}
do_test wal-20.3 {
  close $::buddy

  execsql { PRAGMA wal_checkpoint }
  execsql { SELECT count(*) FROM t1 }

} {16384}
do_test wal-20.4 {
  db close
  sqlite3 db test.db
  execsql { SELECT count(*) FROM t1 }
} {16384}
integrity_check wal-20.5

    PRAGMA cache_size = 10;
    PRAGMA wal_checkpoint;
    BEGIN;
      SAVEPOINT s;
        INSERT INTO t1 SELECT randomblob(900), randomblob(900) FROM t1;
      ROLLBACK TO s;
    COMMIT;

  }
  execsql { SELECT * FROM t1 }
} {1 2 3 4 5 6 7 8 9 10 11 12}
do_test wal-21.3 {
  execsql { PRAGMA integrity_check }
} {ok}

#-------------------------------------------------------------------------
# Test reading and writing of databases with different page-sizes.

  sqlite3 db test.db
  execsql {
    PRAGMA journal_mode = WAL;
    CREATE TABLE data(x);
    INSERT INTO data VALUES('need xShmOpen to see this');
    PRAGMA wal_checkpoint;
  }
} {wal 0 5 5}
do_test wal2-4.2 {
  db close
  testvfs tvfs -noshm 1
  sqlite3 db test.db -vfs tvfs
  catchsql { SELECT * FROM data }
} {1 {unable to open database file}}
do_test wal2-4.3 {

    PRAGMA journal_mode = wal;
    PRAGMA locking_mode = exclusive;
    CREATE TABLE t2(a, b);
    PRAGMA wal_checkpoint;
    INSERT INTO t2 VALUES('I', 'II');
    PRAGMA journal_mode;
  }
} {wal exclusive 0 3 3 wal}
do_test wal2-6.5.2 {
  execsql {
    PRAGMA locking_mode = normal;
    INSERT INTO t2 VALUES('III', 'IV');
    PRAGMA locking_mode = exclusive;
    SELECT * FROM t2;
  }
} {normal exclusive I II III IV}
do_test wal2-6.5.3 {
  execsql { PRAGMA wal_checkpoint }
} {0 4 4}
db close

proc lock_control {method filename handle spec} {
  foreach {start n op type} $spec break
  if {$op == "lock"} { return SQLITE_IOERR }
  return SQLITE_OK
}

  execsql {
    PRAGMA auto_vacuum=OFF;
    PRAGMA page_size = 1024;
    PRAGMA journal_mode = WAL;
    CREATE TABLE t1(x);
    INSERT INTO t1 VALUES(zeroblob(8188*1020));
    CREATE TABLE t2(y);
    PRAGMA wal_checkpoint;
  }
  execsql {

    SELECT rootpage>=8192 FROM sqlite_master WHERE tbl_name = 't2';
  }
} {1}
do_test wal2-8.1.3 {
  execsql {
    PRAGMA cache_size = 10;
    CREATE TABLE t3(z);

do_test wal3-6.1.2 {
  sqlite3 db2 test.db
  sqlite3 db3 test.db
  execsql { BEGIN ; SELECT * FROM t1 } db3
} {o t t f}
do_test wal3-6.1.3 {
  execsql { PRAGMA wal_checkpoint } db2
} {0 7 7}

# At this point the log file has been fully checkpointed. However, 
# connection [db3] holds a lock that prevents the log from being wrapped.
# Test case 3.6.1.4 has [db] attempt a read-lock on aReadMark[0]. But
# as it is obtaining the lock, [db2] appends to the log file.
#
T filter xShmLock

      BEGIN;
      SELECT * FROM t1;
    }]
  }
}
do_test wal3-6.2.2 {
  execsql { PRAGMA wal_checkpoint }
} {0 7 7}
do_test wal3-6.2.3 {
  set ::R
} {h h l b}
do_test wal3-6.2.4 {
  set sz1 [file size test.db-wal]
  execsql { INSERT INTO t1 VALUES('b', 'c'); }
  set sz2 [file size test.db-wal]

    PRAGMA journal_mode = WAL;
    CREATE TABLE b(c);
    INSERT INTO b VALUES('Tehran');
    INSERT INTO b VALUES('Qom');
    INSERT INTO b VALUES('Markazi');
    PRAGMA wal_checkpoint;
  }
} {wal 0 9 9}
do_test wal3-8.2 {
  execsql { SELECT * FROM b }
} {Tehran Qom Markazi}
do_test wal3-8.3 {
  db eval { SELECT * FROM b } {
    db eval { INSERT INTO b VALUES('Qazvin') }
    set r [db2 eval { SELECT * FROM b }]

# 2010 April 13
#
# 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 regression tests for SQLite library.  The
# focus of this file is testing the operation of "blocking-checkpoint"
# operations.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
source $testdir/lock_common.tcl
source $testdir/wal_common.tcl
ifcapable !wal {finish_test ; return }

set testprefix wal5

proc db_page_count  {{file test.db}} { expr [file size $file] / 1024 }
proc wal_page_count {{file test.db}} { wal_frame_count ${file}-wal 1024 }


do_multiclient_test tn {


  set ::nBusyHandler 0
  set ::busy_handler_script ""
  proc busyhandler {n} {
    incr ::nBusyHandler 
    eval $::busy_handler_script
    return 0
  }

  proc reopen_all {} {
    code1 {db close}
    code2 {db2 close}
    code3 {db3 close}
    code1 {sqlite3 db test.db}
    code2 {sqlite3 db2 test.db}
    code3 {sqlite3 db3 test.db}
    sql1  { PRAGMA synchronous = NORMAL }
    code1 { db busy busyhandler }
  }

  do_test 1.$tn.1 {
    reopen_all
    sql1 {
      PRAGMA page_size = 1024;
      PRAGMA auto_vacuum = 0;
      CREATE TABLE t1(x, y);
      PRAGMA journal_mode = WAL;
      INSERT INTO t1 VALUES(1, zeroblob(1200));
      INSERT INTO t1 VALUES(2, zeroblob(1200));
      INSERT INTO t1 VALUES(3, zeroblob(1200));
    }
    expr [file size test.db] / 1024
  } {2}

  # Have connection 2 grab a read-lock on the current snapshot.
  do_test 1.$tn.2 { sql2 { BEGIN; SELECT x FROM t1 } } {1 2 3}

  # Attempt a checkpoint.
  do_test 1.$tn.3 {
    sql1 { PRAGMA wal_checkpoint }
    list [db_page_count] [wal_page_count]
  } {5 9}

  # Write to the db again. The log cannot wrap because of the lock still
  # held by connection 2. The busy-handler has not yet been invoked.
  do_test 1.$tn.4 {
    sql1 { INSERT INTO t1 VALUES(4, zeroblob(1200)) }
    list [db_page_count] [wal_page_count] $::nBusyHandler
  } {5 12 0}

  # Now do a blocking-checkpoint. Set the busy-handler up so that connection
  # 2 releases its lock on the 6th invocation. The checkpointer should then
  # proceed to checkpoint the entire log file. Next write should go to the 
  # start of the log file.
  #
  set ::busy_handler_script { if {$n==5} { sql2 COMMIT } }
  do_test 1.$tn.5 {
    sql1 { PRAGMA wal_checkpoint = RESTART }
    list [db_page_count] [wal_page_count] $::nBusyHandler
  } {6 12 6}
  do_test 1.$tn.6 {
    set ::nBusyHandler 0
    sql1 { INSERT INTO t1 VALUES(5, zeroblob(1200)) }
    list [db_page_count] [wal_page_count] $::nBusyHandler
  } {6 12 0}

  do_test 1.$tn.7 {
    reopen_all
    list [db_page_count] [wal_page_count] $::nBusyHandler
  } {7 0 0}

  do_test 1.$tn.8  { sql2 { BEGIN ; SELECT x FROM t1 } } {1 2 3 4 5}
  do_test 1.$tn.9  {
    sql1 { INSERT INTO t1 VALUES(6, zeroblob(1200)) }
    list [db_page_count] [wal_page_count] $::nBusyHandler
  } {7 5 0}
  do_test 1.$tn.10 { sql3 { BEGIN ; SELECT x FROM t1 } } {1 2 3 4 5 6}

  set ::busy_handler_script { 
    if {$n==5} { sql2 COMMIT } 
    if {$n==6} { set ::db_file_size [db_page_count] }
    if {$n==7} { sql3 COMMIT }
  }
  do_test 1.$tn.11 {
    sql1 { PRAGMA wal_checkpoint = RESTART }
    list [db_page_count] [wal_page_count] $::nBusyHandler
  } {10 5 8}
  do_test 1.$tn.12 { set ::db_file_size } 10
}


#-------------------------------------------------------------------------
# This block of tests explores checkpoint operations on more than one 
# database file.
#
proc setup_and_attach_aux {} {
  sql1 { ATTACH 'test.db2' AS aux }
  sql2 { ATTACH 'test.db2' AS aux }
  sql3 { ATTACH 'test.db2' AS aux }
  sql1 {
    PRAGMA main.page_size=1024; PRAGMA main.journal_mode=WAL;
    PRAGMA aux.page_size=1024;  PRAGMA aux.journal_mode=WAL;
  }
}

proc file_page_counts {} {
  list [db_page_count  test.db ] \
       [wal_page_count test.db ] \
       [db_page_count  test.db2] \
       [wal_page_count test.db2]
}

# Test that executing "PRAGMA wal_checkpoint" checkpoints all attached
# databases, not just the main db.
#
do_multiclient_test tn {
  setup_and_attach_aux
  do_test 2.1.$tn.1 {
    sql1 {
      CREATE TABLE t1(a, b);
      INSERT INTO t1 VALUES(1, 2);
      CREATE TABLE aux.t2(a, b);
      INSERT INTO t2 VALUES(1, 2);
    }
  } {}
  do_test 2.2.$tn.2 { file_page_counts } {1 5 1 5}
  do_test 2.1.$tn.3 { sql1 { PRAGMA wal_checkpoint } } {0 5 5}
  do_test 2.1.$tn.4 { file_page_counts } {2 5 2 5}
}

do_multiclient_test tn {
  setup_and_attach_aux
  do_test 2.2.$tn.1 {
    execsql {
      CREATE TABLE t1(a, b);
      INSERT INTO t1 VALUES(1, 2);
      CREATE TABLE aux.t2(a, b);
      INSERT INTO t2 VALUES(1, 2);
      INSERT INTO t2 VALUES(3, 4);
    }
  } {}
  do_test 2.2.$tn.2 { file_page_counts } {1 5 1 7}
  do_test 2.2.$tn.3 { sql2 { BEGIN; SELECT * FROM t1 } } {1 2}
  do_test 2.2.$tn.4 { sql1 { PRAGMA wal_checkpoint = RESTART } } {1 5 5}
  do_test 2.2.$tn.5 { file_page_counts } {2 5 2 7}
}

do_multiclient_test tn {
  setup_and_attach_aux
  do_test 2.3.$tn.1 {
    execsql {
      CREATE TABLE t1(a, b);
      INSERT INTO t1 VALUES(1, 2);
      CREATE TABLE aux.t2(a, b);
      INSERT INTO t2 VALUES(1, 2);
    }
  } {}
  do_test 2.3.$tn.2 { file_page_counts } {1 5 1 5}
  do_test 2.3.$tn.3 { sql2 { BEGIN; SELECT * FROM t1 } } {1 2}
  do_test 2.3.$tn.4 { sql1 { INSERT INTO t1 VALUES(3, 4) } } {}
  do_test 2.3.$tn.5 { sql1 { INSERT INTO t2 VALUES(3, 4) } } {}
  do_test 2.3.$tn.6 { file_page_counts } {1 7 1 7}
  do_test 2.3.$tn.7 { sql1 { PRAGMA wal_checkpoint = FULL } } {1 7 5}
  do_test 2.3.$tn.8 { file_page_counts } {1 7 2 7}
}

# Check that checkpoints block on the correct locks. And respond correctly
# if they cannot obtain those locks. There are three locks that a checkpoint
# may block on (in the following order):
#
#   1. The writer lock: FULL and RESTART checkpoints block until any writer
#      process releases its lock.
#
#   2. Readers using part of the log file. FULL and RESTART checkpoints block
#      until readers using part (but not all) of the log file have finished.
#
#   3. Readers using any of the log file. After copying data into the
#      database file, RESTART checkpoints block until readers using any part
#      of the log file have finished.
#
# This test case involves running a checkpoint while there exist other 
# processes holding all three types of locks.
#
foreach {tn1 checkpoint busy_on ckpt_expected expected} {
  1   PASSIVE   -   {0 5 5}   -
  2   TYPO      -   {0 5 5}   -

  3   FULL      -   {0 7 7}   2
  4   FULL      1   {1 5 5}   1
  5   FULL      2   {1 7 5}   2
  6   FULL      3   {0 7 7}   2

  7   RESTART   -   {0 7 7}   3
  8   RESTART   1   {1 5 5}   1
  9   RESTART   2   {1 7 5}   2
  10  RESTART   3   {1 7 7}   3

} {
  do_multiclient_test tn {
    setup_and_attach_aux
  
    proc busyhandler {x} {
      set ::max_busyhandler $x
      if {$::busy_on!="-" && $x==$::busy_on} { return 1 }
      switch -- $x {
        1 { sql2 "COMMIT ; BEGIN ; SELECT * FROM t1" }
        2 { sql3 "COMMIT" }
        3 { sql2 "COMMIT" }
      }
      return 0
    }
    set ::max_busyhandler -
  
    do_test 2.4.$tn1.$tn.1 {
      sql1 {
        CREATE TABLE t1(a, b);
        INSERT INTO t1 VALUES(1, 2);
      }
      sql2 { BEGIN; INSERT INTO t1 VALUES(3, 4) }
      sql3 { BEGIN; SELECT * FROM t1 }
    } {1 2}
  
    do_test 2.4.$tn1.$tn.2 {
      code1 { db busy busyhandler }
      sql1 "PRAGMA wal_checkpoint = $checkpoint"
    } $ckpt_expected
    do_test 2.4.$tn1.$tn.3 { set ::max_busyhandler } $expected
  }
}


finish_test

#

proc wal_file_size {nFrame pgsz} {
  expr {32 + ($pgsz+24)*$nFrame}
}

proc wal_frame_count {zFile pgsz} {
  if {[file exists $zFile]==0} { return 0 }
  set f [file size $zFile]
  if {$f < 32} { return 0 }
  expr {($f - 32) / ($pgsz+24)}
}

proc wal_cksum_intlist {ckv1 ckv2 intlist} {
  upvar $ckv1 c1
  upvar $ckv2 c2
  foreach {v1 v2} $intlist {