SQLite

2.8.0

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.73 2003/02/11 14:55:41 drh Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

  u8 inJournal;                  /* TRUE if has been written to journal */
  u8 inCkpt;                     /* TRUE if written to the checkpoint journal */
  u8 dirty;                      /* TRUE if we need to write back changes */
  u8 needSync;                   /* Sync journal before writing this page */
  u8 alwaysRollback;             /* Disable dont_rollback() for this page */
  PgHdr *pDirty;                 /* Dirty pages sorted by PgHdr.pgno */
  /* SQLITE_PAGE_SIZE bytes of page data follow this header */
  /* Pager.nExtra bytes of local data follow the page data and checksum */
};

/*
** Convert a pointer to a PgHdr into a pointer to its data
** and back again.
*/
#define PGHDR_TO_DATA(P)  ((void*)(&(P)[1]))

  int dbSize;                 /* Number of pages in the file */
  int origDbSize;             /* dbSize before the current change */
  int ckptSize;               /* Size of database (in pages) at ckpt_begin() */
  off_t ckptJSize;            /* Size of journal at ckpt_begin() */
#ifndef NDEBUG
  off_t syncJSize;            /* Size of journal at last fsync() call */
#endif
  int nRec;                   /* Number of pages written to the journal */
  u32 cksumInit;              /* Quasi-random value added to every checksum */
  int ckptNRec;               /* Number of records in the checkpoint journal */
  int nExtra;                 /* Add this many bytes to each in-memory page */
  void (*xDestructor)(void*); /* Call this routine when freeing pages */
  int nPage;                  /* Total number of in-memory pages */
  int nRef;                   /* Number of in-memory pages with PgHdr.nRef>0 */
  int mxPage;                 /* Maximum number of pages to hold in cache */
  int nHit, nMiss, nOvfl;     /* Cache hits, missing, and LRU overflows */
  u8 journalOpen;             /* True if journal file descriptors is valid */
  u8 journalStarted;          /* True if initial magic of journal is synced */
  u8 useJournal;              /* Do not use a rollback journal on this file */
  u8 ckptOpen;                /* True if the checkpoint journal is open */
  u8 ckptInUse;               /* True we are in a checkpoint */
  u8 ckptAutoopen;            /* Open ckpt journal when main journal is opened*/
  u8 noSync;                  /* Do not sync the journal if true */
  u8 fullSync;                /* Do extra syncs of the journal for robustness */
  u8 state;                   /* SQLITE_UNLOCK, _READLOCK or _WRITELOCK */
  u8 errMask;                 /* One of several kinds of errors */
  u8 tempFile;                /* zFilename is a temporary file */
  u8 readOnly;                /* True for a read-only database */
  u8 needSync;                /* True if an fsync() is needed on the journal */
  u8 dirtyFile;               /* True if database file has changed in any way */
  u8 alwaysRollback;          /* Disable dont_rollback() for all pages */

  u8 *aInJournal;             /* One bit for each page in the database file */
  u8 *aInCkpt;                /* One bit for each page in the database */
  PgHdr *pFirst, *pLast;      /* List of free pages */
  PgHdr *pFirstSynced;        /* First free page with PgHdr.needSync==0 */
  PgHdr *pAll;                /* List of all pages */
  PgHdr *pCkpt;               /* List of pages in the checkpoint journal */
  PgHdr *aHash[N_PG_HASH];    /* Hash table to map page number of PgHdr */

#define PAGER_ERR_LOCK     0x04  /* error in the locking protocol */
#define PAGER_ERR_CORRUPT  0x08  /* database or journal corruption */
#define PAGER_ERR_DISK     0x10  /* general disk I/O error - bad hard drive? */

/*
** The journal file contains page records in the following
** format.
**
** Actually, this structure is the complete page record for pager
** formats less than 3.  Beginning with format 3, this record is surrounded
** by two checksums.
*/
typedef struct PageRecord PageRecord;
struct PageRecord {
  Pgno pgno;                     /* The page number */
  char aData[SQLITE_PAGE_SIZE];  /* Original data for page pgno */
};

/*
** Journal files begin with the following magic string.  The data
** was obtained from /dev/random.  It is used only as a sanity check.
**
** There are three journal formats (so far). The 1st journal format writes
** 32-bit integers in the byte-order of the host machine.  New
** formats writes integers as big-endian.  All new journals use the
** new format, but we have to be able to read an older journal in order
** to rollback journals created by older versions of the library.
**
** The 3rd journal format (added for 2.8.0) adds additional sanity
** checking information to the journal.  If the power fails while the
** journal is being written, semi-random garbage data might appear in
** the journal file after power is restored.  If an attempt is then made
** to roll the journal back, the database could be corrupted.  The additional
** sanity checking data is an attempt to discover the garbage in the
** journal and ignore it.
**
** The sanity checking information for the 3rd journal format consists
** of a 32-bit checksum on each page of data.  The checksum covers both
** the page number and the SQLITE_PAGE_SIZE bytes of data for the page.
** This cksum is initialized to a 32-bit random value that appears in the
** journal file right after the header.  The random initializer is important,
** because garbage data that appears at the end of a journal is likely
** data that was once in other files that have now been deleted.  If the
** garbage data came from an obsolete journal file, the checksums might
** be correct.  But by initializing the checksum to random value which
** is different for every journal, we minimize that risk.
*/
static const unsigned char aJournalMagic1[] = {
  0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd4,
};
static const unsigned char aJournalMagic2[] = {
  0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd5,
};
static const unsigned char aJournalMagic3[] = {
  0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd6,
};
#define JOURNAL_FORMAT_1 1
#define JOURNAL_FORMAT_2 2
#define JOURNAL_FORMAT_3 3

/*
** The following integer determines what format to use when creating
** new primary journal files.  By default we always use format 3.
** When testing, we can set this value to older journal formats in order to
** make sure that newer versions of the library are able to rollback older
** journal files.
**
** Note that checkpoint journals always use format 2 and omit the header.
*/
#ifdef SQLITE_TEST
int journal_format = 3;
#else
# define journal_format 3
#endif

/*
** The size of the header and of each page in the journal varies according
** to which journal format is being used.  The following macros figure out
** the sizes based on format numbers.
*/
#define JOURNAL_HDR_SZ(X) \
   (sizeof(aJournalMagic1) + sizeof(Pgno) + ((X)>=3)*2*sizeof(u32))
#define JOURNAL_PG_SZ(X) \
   (SQLITE_PAGE_SIZE + sizeof(Pgno) + ((X)>=3)*sizeof(u32))

/*
** Enable reference count tracking here:
*/
#ifdef SQLITE_TEST
  int pager_refinfo_enable = 0;
  static void pager_refinfo(PgHdr *p){
    static int cnt = 0;

#else
# define REFINFO(X)
#endif

/*
** Read a 32-bit integer from the given file descriptor
*/
static int read32bits(int format, OsFile *fd, u32 *pRes){
  u32 res;
  int rc;
  rc = sqliteOsRead(fd, &res, sizeof(res));
  if( rc==SQLITE_OK && format>JOURNAL_FORMAT_1 ){
    unsigned char ac[4];
    memcpy(ac, &res, 4);
    res = (ac[0]<<24) | (ac[1]<<16) | (ac[2]<<8) | ac[3];
  }
  *pRes = res;
  return rc;
}

/*
** Write a 32-bit integer into the given file descriptor.  Writing
** is always done using the new journal format.
*/
static int write32bits(OsFile *fd, u32 val){
  unsigned char ac[4];
  if( journal_format<=1 ){
    return sqliteOsWrite(fd, &val, 4);
  }
  ac[0] = (val>>24) & 0xff;
  ac[1] = (val>>16) & 0xff;
  ac[2] = (val>>8) & 0xff;
  ac[3] = val & 0xff;
  return sqliteOsWrite(fd, ac, 4);
}

/*
** Write a 32-bit integer into a page header right before the
** page data.  This will overwrite the PgHdr.pDirty pointer.
*/
static void store32bits(u32 val, PgHdr *p, int offset){

  unsigned char *ac;
  ac = &((char*)PGHDR_TO_DATA(p))[offset];
  if( journal_format<=1 ){
    memcpy(ac, &val, 4);
  }else{
    ac[0] = (val>>24) & 0xff;
    ac[1] = (val>>16) & 0xff;
    ac[2] = (val>>8) & 0xff;
    ac[3] = val & 0xff;
  }

    ** child process does the COMMIT.  Because of the semantics of unix
    ** file locking, the unlock will fail.
    */
    pPager->state = SQLITE_UNLOCK;
  }
  return rc;
}

/*
** Compute and return a checksum for the page of data.
*/
static u32 pager_cksum(Pager *pPager, Pgno pgno, const char *aData){
  u32 cksum = pPager->cksumInit + pgno;
  /* const u8 *a = (const u8*)aData;
  int i;
  for(i=0; i<SQLITE_PAGE_SIZE; i++){ cksum += a[i]; } */
  /* fprintf(stderr,"CKSUM for %p(%08x) page %d: %08x\n", pPager, pPager->cksumInit, pgno, cksum); */
  return cksum;
}

/*
** Read a single page from the journal file opened on file descriptor
** jfd.  Playback this one page.
**
** There are three different journal formats.  The format parameter determines
** which format is used by the journal that is played back.
*/
static int pager_playback_one_page(Pager *pPager, OsFile *jfd, int format){
  int rc;
  PgHdr *pPg;              /* An existing page in the cache */
  PageRecord pgRec;
  u32 cksum;

  rc = read32bits(format, jfd, &pgRec.pgno);
  if( rc!=SQLITE_OK ) return SQLITE_DONE;
  rc = sqliteOsRead(jfd, &pgRec.aData, sizeof(pgRec.aData));
  if( rc!=SQLITE_OK ) return SQLITE_DONE;

  /* Sanity checking on the page.  This is more important that I originally
  ** thought.  If a power failure occurs while the journal is being written,
  ** it could cause invalid data to be written into the journal.  We need to
  ** detect this invalid data (with high probability) and ignore it.
  */
  if( pgRec.pgno==0 ){
    return SQLITE_DONE;
  }
  if( pgRec.pgno>pPager->dbSize ){
    return SQLITE_OK;
  }
  if( format>=JOURNAL_FORMAT_3 ){
    rc = read32bits(format, jfd, &cksum);
    if( rc ) return SQLITE_DONE;
    if( pager_cksum(pPager, pgRec.pgno, pgRec.aData)!=cksum ){
      return SQLITE_DONE;
    }
  }

  /* Playback the page.  Update the in-memory copy of the page
  ** at the same time, if there is one.
  */
  pPg = pager_lookup(pPager, pgRec.pgno);
  if( pPg==0 || pPg->needSync==0 ){
    TRACE2("PLAYBACK %d\n", pgRec.pgno);

** at the beginning) then this routine returns SQLITE_PROTOCOL.
** If any other errors occur during playback, the database will
** likely be corrupted, so the PAGER_ERR_CORRUPT bit is set in
** pPager->errMask and SQLITE_CORRUPT is returned.  If it all
** works, then this routine returns SQLITE_OK.
*/
static int pager_playback(Pager *pPager){
  off_t szJ;               /* Size of the journal file in bytes */
  int nRec;                /* Number of Records in the journal */
  int i;                   /* Loop counter */
  Pgno mxPg = 0;           /* Size of the original file in pages */
  int format;              /* Format of the journal file. */
  unsigned char aMagic[sizeof(aJournalMagic1)];
  int rc;

  /* Figure out how many records are in the journal.  Abort early if
  ** the journal is empty.
  */
  assert( pPager->journalOpen );
  sqliteOsSeek(&pPager->jfd, 0);
  rc = sqliteOsFileSize(&pPager->jfd, &szJ);
  if( rc!=SQLITE_OK ){
    goto end_playback;
  }
  if( szJ < sizeof(aMagic)+sizeof(Pgno) ){
    goto end_playback;
  }


  /* Read the beginning of the journal and truncate the
  ** database file back to its original size.
  */
  rc = sqliteOsRead(&pPager->jfd, aMagic, sizeof(aMagic));
  if( rc!=SQLITE_OK ){
    rc = SQLITE_PROTOCOL;
    goto end_playback;
  }
  if( memcmp(aMagic, aJournalMagic3, sizeof(aMagic))==0 ){
    format = JOURNAL_FORMAT_3;
  }else if( memcmp(aMagic, aJournalMagic2, sizeof(aMagic))==0 ){
    format = JOURNAL_FORMAT_2;
  }else if( memcmp(aMagic, aJournalMagic1, sizeof(aMagic))==0 ){
    format = JOURNAL_FORMAT_1;
  }else{
    rc = SQLITE_PROTOCOL;
    goto end_playback;
  }
  if( format>=JOURNAL_FORMAT_3 ){
    rc = read32bits(format, &pPager->jfd, &nRec);
    if( rc ) goto end_playback;
    rc = read32bits(format, &pPager->jfd, &pPager->cksumInit);
    if( rc ) goto end_playback;
    if( nRec==0xffffffff ){
      nRec = (szJ - JOURNAL_HDR_SZ(3))/JOURNAL_PG_SZ(3);
    }
  }else{
    nRec = (szJ - (sizeof(aMagic)+sizeof(Pgno))) / sizeof(PageRecord);
  }
  rc = read32bits(format, &pPager->jfd, &mxPg);
  if( rc!=SQLITE_OK ){
    goto end_playback;
  }
  rc = sqliteOsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)mxPg);
  if( rc!=SQLITE_OK ){
    goto end_playback;
  }
  pPager->dbSize = mxPg;
  
  /* Copy original pages out of the journal and back into the database file.
  */
  for(i=0; i<nRec; i++){
    rc = pager_playback_one_page(pPager, &pPager->jfd, format);
    if( rc!=SQLITE_OK ){
      if( rc==SQLITE_DONE ){
fprintf(stderr,"Playback complete after %d of %d records\n", i, nRec);
        rc = SQLITE_OK;
      }
      break;
    }
  }


end_playback:
#if !defined(NDEBUG) && defined(SQLITE_TEST)
  /* For pages that were never written into the journal, restore the
  ** memory copy from the original database file.

**         journal file itself.
**
**    (2)  In addition to playing back the checkpoint journal, also
**         playback all pages of the transaction journal beginning
**         at offset pPager->ckptJSize.
*/
static int pager_ckpt_playback(Pager *pPager){
  off_t szJ;               /* Size of the full journal */
  int nRec;                /* Number of Records */
  int i;                   /* Loop counter */
  int rc;

  /* Truncate the database back to its original size.
  */
  rc = sqliteOsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)pPager->ckptSize);
  pPager->dbSize = pPager->ckptSize;

  /* Figure out how many records are in the checkpoint journal.
  */
  assert( pPager->ckptInUse && pPager->journalOpen );
  sqliteOsSeek(&pPager->cpfd, 0);
  nRec = pPager->ckptNRec;
  
  /* Copy original pages out of the checkpoint journal and back into the
  ** database file.  Note that the checkpoint journal always uses format
  ** 2 instead of format 3 since it does not need to be concerned with
  ** power failures corrupting the journal and can thus omit the checksums.
  */





  for(i=nRec-1; i>=0; i--){
    rc = pager_playback_one_page(pPager, &pPager->cpfd, 2);
    assert( rc!=SQLITE_DONE );
    if( rc!=SQLITE_OK ) goto end_ckpt_playback;
  }

  /* Figure out how many pages need to be copied out of the transaction
  ** journal.
  */
  rc = sqliteOsSeek(&pPager->jfd, pPager->ckptJSize);
  if( rc!=SQLITE_OK ){
    goto end_ckpt_playback;
  }
  rc = sqliteOsFileSize(&pPager->jfd, &szJ);
  if( rc!=SQLITE_OK ){
    goto end_ckpt_playback;
  }
  nRec = (szJ - pPager->ckptJSize)/JOURNAL_PG_SZ(journal_format);
  for(i=nRec-1; i>=0; i--){
    rc = pager_playback_one_page(pPager, &pPager->jfd, journal_format);
    if( rc!=SQLITE_OK ){
      assert( rc!=SQLITE_DONE );
      goto end_ckpt_playback;
    }
  }
  
end_ckpt_playback:
  if( rc!=SQLITE_OK ){
    pPager->errMask |= PAGER_ERR_CORRUPT;
    rc = SQLITE_CORRUPT;
  }
  return rc;
}

  int rc = SQLITE_OK;

  /* Sync the journal before modifying the main database
  ** (assuming there is a journal and it needs to be synced.)
  */
  if( pPager->needSync ){
    if( !pPager->tempFile ){
      off_t szJ;
      assert( pPager->journalOpen );
      assert( !pPager->noSync );
#ifndef NDEBUG
      {
        off_t hdrSz, pgSz;
        hdrSz = JOURNAL_HDR_SZ(journal_format);
        pgSz = JOURNAL_PG_SZ(journal_format);
        rc = sqliteOsFileSize(&pPager->jfd, &pPager->syncJSize);
        if( rc!=0 ) return rc;
        assert( pPager->nRec*pgSz+hdrSz==pPager->syncJSize );
      }
#endif
      if( pPager->fullSync ){
        TRACE1("SYNC\n");
        rc = sqliteOsSync(&pPager->jfd);
        if( rc!=0 ) return rc;

      }
      sqliteOsSeek(&pPager->jfd, sizeof(aJournalMagic1));
      write32bits(&pPager->jfd, pPager->nRec);
      szJ = JOURNAL_HDR_SZ(journal_format) +
               pPager->nRec*JOURNAL_PG_SZ(journal_format);
      sqliteOsSeek(&pPager->jfd, szJ);
      TRACE1("SYNC\n");
      rc = sqliteOsSync(&pPager->jfd);
      if( rc!=0 ) return rc;

      pPager->journalStarted = 1;
    }
    pPager->needSync = 0;

    /* Erase the needSync flag from every page.
    */
    for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){

  }
  if( pPg==0 ){
    /* The requested page is not in the page cache. */
    int h;
    pPager->nMiss++;
    if( pPager->nPage<pPager->mxPage || pPager->pFirst==0 ){
      /* Create a new page */
      pPg = sqliteMallocRaw( sizeof(*pPg) + SQLITE_PAGE_SIZE 
                              + sizeof(u32) + pPager->nExtra );
      if( pPg==0 ){
        *ppPage = 0;
        pager_unwritelock(pPager);
        pPager->errMask |= PAGER_ERR_MEM;
        return SQLITE_NOMEM;
      }
      memset(pPg, 0, sizeof(*pPg));

    pPager->state = SQLITE_READLOCK;
    return SQLITE_CANTOPEN;
  }
  pPager->journalOpen = 1;
  pPager->journalStarted = 0;
  pPager->needSync = 0;
  pPager->alwaysRollback = 0;
  pPager->nRec = 0;
  sqlitepager_pagecount(pPager);
  pPager->origDbSize = pPager->dbSize;
  if( journal_format==JOURNAL_FORMAT_3 ){
    rc = sqliteOsWrite(&pPager->jfd, aJournalMagic3, sizeof(aJournalMagic3));
    if( rc==SQLITE_OK ){
      rc = write32bits(&pPager->jfd, pPager->tempFile ? 0xffffffff : 0);
    }
    if( rc==SQLITE_OK ){
      pPager->cksumInit = (u32)sqliteRandomInteger();
      rc = write32bits(&pPager->jfd, pPager->cksumInit);
    }
  }else if( journal_format==JOURNAL_FORMAT_2 ){
    rc = sqliteOsWrite(&pPager->jfd, aJournalMagic2, sizeof(aJournalMagic2));
  }else{
    assert( journal_format==JOURNAL_FORMAT_1 );
    rc = sqliteOsWrite(&pPager->jfd, aJournalMagic1, sizeof(aJournalMagic1));
  }
  if( rc==SQLITE_OK ){
    rc = write32bits(&pPager->jfd, pPager->dbSize);
  }
  if( pPager->ckptAutoopen && rc==SQLITE_OK ){
    rc = sqlitepager_ckpt_begin(pPager);
  }

  /* The transaction journal now exists and we have a write lock on the
  ** main database file.  Write the current page to the transaction 
  ** journal if it is not there already.
  */
  if( !pPg->inJournal && pPager->useJournal ){
    if( (int)pPg->pgno <= pPager->origDbSize ){
      int szPg;
      u32 saved;
      if( journal_format>=JOURNAL_FORMAT_3 ){
        u32 cksum = pager_cksum(pPager, pPg->pgno, pData);
        saved = *(u32*)PGHDR_TO_EXTRA(pPg);
        store32bits(cksum, pPg, SQLITE_PAGE_SIZE);
        szPg = SQLITE_PAGE_SIZE+8;
      }else{
        szPg = SQLITE_PAGE_SIZE+4;
      }
      store32bits(pPg->pgno, pPg, -4);
      rc = sqliteOsWrite(&pPager->jfd, &((char*)pData)[-4], szPg);
      if( journal_format>=JOURNAL_FORMAT_3 ){
        *(u32*)PGHDR_TO_EXTRA(pPg) = saved;
      }
      pPager->nRec++;
      if( rc!=SQLITE_OK ){
        sqlitepager_rollback(pPager);
        pPager->errMask |= PAGER_ERR_FULL;
        return rc;
      }
      assert( pPager->aInJournal!=0 );
      pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);

    }
    if( pPg->needSync ){
      pPager->needSync = 1;
    }
  }

  /* If the checkpoint journal is open and the page is not in it,
  ** then write the current page to the checkpoint journal.  Note that
  ** the checkpoint journal always uses the simplier format 2 that lacks
  ** checksums.  The header is also omitted from the checkpoint journal.
  */
  if( pPager->ckptInUse && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){
    assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
    store32bits(pPg->pgno, pPg, -4);
    rc = sqliteOsWrite(&pPager->cpfd, &((char*)pData)[-4], SQLITE_PAGE_SIZE+4);
    if( rc!=SQLITE_OK ){
      sqlitepager_rollback(pPager);
      pPager->errMask |= PAGER_ERR_FULL;
      return rc;
    }
    pPager->ckptNRec++;

  /* Truncate the journal to the size it was at the conclusion of the
  ** last sqliteOsSync() call.  This is really an error check.  If the
  ** rollback still works, it means that the rollback would have also
  ** worked if it had occurred after an OS crash or unexpected power
  ** loss.
  */
  if( !pPager->noSync ){
    int m = JOURNAL_HDR_SZ(journal_format);
    assert( !pPager->tempFile );
    if( pPager->syncJSize<m ){
      pPager->syncJSize = m;
    }
    TRACE2("TRUNCATE JOURNAL %lld\n", pPager->syncJSize);
    rc =  sqliteOsTruncate(&pPager->jfd, pPager->syncJSize);
    if( rc ) return rc;
    pPager->nRec = 0;
  }
#endif

  if( pPager->errMask!=0 && pPager->errMask!=PAGER_ERR_FULL ){
    if( pPager->state>=SQLITE_WRITELOCK ){
      pager_playback(pPager);
    }

  assert( pPager->journalOpen );
  assert( !pPager->ckptInUse );
  pPager->aInCkpt = sqliteMalloc( pPager->dbSize/8 + 1 );
  if( pPager->aInCkpt==0 ){
    sqliteOsReadLock(&pPager->fd);
    return SQLITE_NOMEM;
  }
#ifndef NDEBUG
  rc = sqliteOsFileSize(&pPager->jfd, &pPager->ckptJSize);
  if( rc ) goto ckpt_begin_failed;
  assert( pPager->ckptJSize == 
    pPager->nRec*JOURNAL_PG_SZ(journal_format)+JOURNAL_HDR_SZ(journal_format) );
#endif
  pPager->ckptJSize = pPager->nRec*JOURNAL_PG_SZ(journal_format)
                         + JOURNAL_HDR_SZ(journal_format);
  pPager->ckptSize = pPager->dbSize;
  if( !pPager->ckptOpen ){
    rc = sqlitepager_opentemp(zTemp, &pPager->cpfd);
    if( rc ) goto ckpt_begin_failed;
    pPager->ckptOpen = 1;
    pPager->ckptNRec = 0;
  }

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.19 2003/02/11 14:55:41 drh Exp $
*/

/*
** The size of one page
**
** You can change this value to another (reasonable) power of two
** such as 512, 2048, 4096, or 8192 and things will still work.  But

void sqlitepager_dont_rollback(void*);
void sqlitepager_dont_write(Pager*, Pgno);
int *sqlitepager_stats(Pager*);

#ifdef SQLITE_TEST
void sqlitepager_refdump(Pager*);
int pager_refinfo_enable;
int journal_format;
#endif

/*
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.160 2003/02/11 14:55:41 drh Exp $
*/
#include "config.h"
#include "sqlite.h"
#include "hash.h"
#include "vdbe.h"
#include "parse.h"
#include "btree.h"

** RESTRICT, SETNULL, and CASCADE actions apply only to foreign keys.
** RESTRICT is the same as ABORT for IMMEDIATE foreign keys and the
** same as ROLLBACK for DEFERRED keys.  SETNULL means that the foreign
** key is set to NULL.  CASCADE means that a DELETE or UPDATE of the
** referenced table row is propagated into the row that holds the
** foreign key.
** 
** The following symbolic values are used to record which type
** of action to take.
*/
#define OE_None     0   /* There is no constraint to check */
#define OE_Rollback 1   /* Fail the operation and rollback the transaction */
#define OE_Abort    2   /* Back out changes but do no rollback transaction */
#define OE_Fail     3   /* Stop the operation but leave all prior changes */
#define OE_Ignore   4   /* Ignore the error. Do not do the INSERT or UPDATE */

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the pager.c module in SQLite.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test2.c,v 1.15 2003/02/11 14:55:41 drh Exp $
*/
#include "os.h"
#include "sqliteInt.h"
#include "pager.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

  int i;
  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
  }
  Tcl_LinkVar(interp, "sqlite_io_error_pending",
     (char*)&sqlite_io_error_pending, TCL_LINK_INT);
#ifdef SQLITE_TEST
  Tcl_LinkVar(interp, "journal_format",
     (char*)&journal_format, TCL_LINK_INT);
#endif
  return TCL_OK;
}

# 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 implements regression tests for SQLite library.  The
# focus of this script is database locks.
#
# $Id: trans.test,v 1.17 2003/02/11 14:55:42 drh Exp $


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


# Create several tables to work with.

}

# Do rollbacks.  Make sure the signature does not change.
#
for {set i 2} {$i<=$limit} {incr i} {
  set ::sig [signature]
  set cnt [lindex $::sig 0]
  set ::journal_format [expr {($i%3)+1}]
  do_test trans-9.$i.1-$cnt {
     execsql {
       BEGIN;
       DELETE FROM t3 WHERE random()%10!=0;
       INSERT INTO t3 SELECT randstr(10,10)||x FROM t3;
       INSERT INTO t3 SELECT randstr(10,10)||x FROM t3;
       ROLLBACK;