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Overview
Comment:Simplifications and performance improvement in pager_write().
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: ab7aeeead395a05b91a921ef9ebe9252fffad667
User & Date: drh 2015-06-29 14:11:50
Context
2015-06-29
15:41
Fix minor problems in the ota demo application. check-in: 6aaaec6e user: dan tags: trunk
14:11
Simplifications and performance improvement in pager_write(). check-in: ab7aeeea user: drh tags: trunk
04:21
Add the new PGHDR_CLEAN bit to PgHdr.flags in pcache.c. This bit is always the opposite of PGHDR_DIRTY. Use the extra bit to avoid a comparison for a small performance boost. check-in: 8619fc34 user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/bitvec.c.

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}

/*
** Check to see if the i-th bit is set.  Return true or false.
** If p is NULL (if the bitmap has not been created) or if
** i is out of range, then return false.
*/
int sqlite3BitvecTest(Bitvec *p, u32 i){
  if( p==0 ) return 0;
  i--;
  if( i>=p->iSize ) return 0;
  while( p->iDivisor ){
    u32 bin = i/p->iDivisor;
    i = i%p->iDivisor;
    p = p->u.apSub[bin];
    if (!p) {
................................................................................
    while( p->u.aHash[h] ){
      if( p->u.aHash[h]==i ) return 1;
      h = (h+1) % BITVEC_NINT;
    }
    return 0;
  }
}




/*
** Set the i-th bit.  Return 0 on success and an error code if
** anything goes wrong.
**
** This routine might cause sub-bitmaps to be allocated.  Failing
** to get the memory needed to hold the sub-bitmap is the only







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}

/*
** Check to see if the i-th bit is set.  Return true or false.
** If p is NULL (if the bitmap has not been created) or if
** i is out of range, then return false.
*/
int sqlite3BitvecTestNotNull(Bitvec *p, u32 i){
  assert( p!=0 );
  i--;
  if( i>=p->iSize ) return 0;
  while( p->iDivisor ){
    u32 bin = i/p->iDivisor;
    i = i%p->iDivisor;
    p = p->u.apSub[bin];
    if (!p) {
................................................................................
    while( p->u.aHash[h] ){
      if( p->u.aHash[h]==i ) return 1;
      h = (h+1) % BITVEC_NINT;
    }
    return 0;
  }
}
int sqlite3BitvecTest(Bitvec *p, u32 i){
  return p!=0 && sqlite3BitvecTestNotNull(p,i);
}

/*
** Set the i-th bit.  Return 0 on success and an error code if
** anything goes wrong.
**
** This routine might cause sub-bitmaps to be allocated.  Failing
** to get the memory needed to hold the sub-bitmap is the only

Changes to src/pager.c.

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**
**   if( isOpen(pPager->jfd) ){ ...
**
** instead of
**
**   if( pPager->jfd->pMethods ){ ...
*/
#define isOpen(pFd) ((pFd)->pMethods)

/*
** Return true if this pager uses a write-ahead log instead of the usual
** rollback journal. Otherwise false.
*/
#ifndef SQLITE_OMIT_WAL
static int pagerUseWal(Pager *pPager){
................................................................................
static int subjRequiresPage(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  PagerSavepoint *p;
  Pgno pgno = pPg->pgno;
  int i;
  for(i=0; i<pPager->nSavepoint; i++){
    p = &pPager->aSavepoint[i];
    if( p->nOrig>=pgno && 0==sqlite3BitvecTest(p->pInSavepoint, pgno) ){
      return 1;
    }
  }
  return 0;
}


/*
** Return true if the page is already in the journal file.
*/
static int pageInJournal(Pager *pPager, PgHdr *pPg){
  return sqlite3BitvecTest(pPager->pInJournal, pPg->pgno);
}


/*
** Read a 32-bit integer from the given file descriptor.  Store the integer
** that is read in *pRes.  Return SQLITE_OK if everything worked, or an
** error code is something goes wrong.
**
** All values are stored on disk as big-endian.
................................................................................
    assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED );
    assert( assert_pager_state(pPager) );
  }

  PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
  return rc;
}






















































/*
** Mark a single data page as writeable. The page is written into the 
** main journal or sub-journal as required. If the page is written into
** one of the journals, the corresponding bit is set in the 
** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs
** of any open savepoints as appropriate.
*/
static int pager_write(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;
  int inJournal;

  /* This routine is not called unless a write-transaction has already 
  ** been started. The journal file may or may not be open at this point.
  ** It is never called in the ERROR state.
  */
  assert( pPager->eState==PAGER_WRITER_LOCKED
       || pPager->eState==PAGER_WRITER_CACHEMOD
       || pPager->eState==PAGER_WRITER_DBMOD
  );
  assert( assert_pager_state(pPager) );
  assert( pPager->errCode==0 );
  assert( pPager->readOnly==0 );

  CHECK_PAGE(pPg);

  /* The journal file needs to be opened. Higher level routines have already
  ** obtained the necessary locks to begin the write-transaction, but the
  ** rollback journal might not yet be open. Open it now if this is the case.
  **
  ** This is done before calling sqlite3PcacheMakeDirty() on the page. 
................................................................................
  if( pPager->eState==PAGER_WRITER_LOCKED ){
    rc = pager_open_journal(pPager);
    if( rc!=SQLITE_OK ) return rc;
  }
  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
  assert( assert_pager_state(pPager) );

  /* Mark the page as dirty.  If the page has already been written
  ** to the journal then we can return right away.
  */
  sqlite3PcacheMakeDirty(pPg);
  inJournal = pageInJournal(pPager, pPg);
  if( inJournal && (pPager->nSavepoint==0 || !subjRequiresPage(pPg)) ){
    assert( !pagerUseWal(pPager) );
  }else{
  
    /* The transaction journal now exists and we have a RESERVED or an
    ** EXCLUSIVE lock on the main database file.  Write the current page to
    ** the transaction journal if it is not there already.



    */
    if( !inJournal && !pagerUseWal(pPager) ){




      assert( pagerUseWal(pPager)==0 );
      if( pPg->pgno<=pPager->dbOrigSize && isOpen(pPager->jfd) ){
        u32 cksum;
        char *pData2;
        i64 iOff = pPager->journalOff;

        /* We should never write to the journal file the page that
        ** contains the database locks.  The following assert verifies
        ** that we do not. */
        assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );

        assert( pPager->journalHdr<=pPager->journalOff );
        CODEC2(pPager, pPg->pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
        cksum = pager_cksum(pPager, (u8*)pData2);

        /* Even if an IO or diskfull error occurs while journalling the
        ** page in the block above, set the need-sync flag for the page.
        ** Otherwise, when the transaction is rolled back, the logic in
        ** playback_one_page() will think that the page needs to be restored
        ** in the database file. And if an IO error occurs while doing so,
        ** then corruption may follow.
        */
        pPg->flags |= PGHDR_NEED_SYNC;

        rc = write32bits(pPager->jfd, iOff, pPg->pgno);
        if( rc!=SQLITE_OK ) return rc;
        rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4);
        if( rc!=SQLITE_OK ) return rc;
        rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum);
        if( rc!=SQLITE_OK ) return rc;

        IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, 
                 pPager->journalOff, pPager->pageSize));
        PAGER_INCR(sqlite3_pager_writej_count);
        PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
             PAGERID(pPager), pPg->pgno, 
             ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));

        pPager->journalOff += 8 + pPager->pageSize;
        pPager->nRec++;
        assert( pPager->pInJournal!=0 );
        rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
        testcase( rc==SQLITE_NOMEM );
        assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
        rc |= addToSavepointBitvecs(pPager, pPg->pgno);

        if( rc!=SQLITE_OK ){
          assert( rc==SQLITE_NOMEM );
          return rc;
        }
      }else{
        if( pPager->eState!=PAGER_WRITER_DBMOD ){
          pPg->flags |= PGHDR_NEED_SYNC;
        }
        PAGERTRACE(("APPEND %d page %d needSync=%d\n",
                PAGERID(pPager), pPg->pgno,
               ((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
      }
    }
  
    /* If the statement journal is open and the page is not in it,
    ** then write the current page to the statement journal.  Note that
    ** the statement journal format differs from the standard journal format
    ** in that it omits the checksums and the header.
    */
    if( pPager->nSavepoint>0 && subjRequiresPage(pPg) ){
      rc = subjournalPage(pPg);
    }
  }

  /* Update the database size and return.
  */
  if( pPager->dbSize<pPg->pgno ){
    pPager->dbSize = pPg->pgno;
  }
  return rc;
}

/*







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**
**   if( isOpen(pPager->jfd) ){ ...
**
** instead of
**
**   if( pPager->jfd->pMethods ){ ...
*/
#define isOpen(pFd) ((pFd)->pMethods!=0)

/*
** Return true if this pager uses a write-ahead log instead of the usual
** rollback journal. Otherwise false.
*/
#ifndef SQLITE_OMIT_WAL
static int pagerUseWal(Pager *pPager){
................................................................................
static int subjRequiresPage(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  PagerSavepoint *p;
  Pgno pgno = pPg->pgno;
  int i;
  for(i=0; i<pPager->nSavepoint; i++){
    p = &pPager->aSavepoint[i];
    if( p->nOrig>=pgno && 0==sqlite3BitvecTestNotNull(p->pInSavepoint, pgno) ){
      return 1;
    }
  }
  return 0;
}

#ifdef SQLITE_DEBUG
/*
** Return true if the page is already in the journal file.
*/
static int pageInJournal(Pager *pPager, PgHdr *pPg){
  return sqlite3BitvecTest(pPager->pInJournal, pPg->pgno);
}
#endif

/*
** Read a 32-bit integer from the given file descriptor.  Store the integer
** that is read in *pRes.  Return SQLITE_OK if everything worked, or an
** error code is something goes wrong.
**
** All values are stored on disk as big-endian.
................................................................................
    assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED );
    assert( assert_pager_state(pPager) );
  }

  PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
  return rc;
}

/*
** Write page pPg onto the end of the rollback journal.
*/
static SQLITE_NOINLINE int pagerAddPageToRollbackJournal(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  int rc;
  u32 cksum;
  char *pData2;
  i64 iOff = pPager->journalOff;

  /* We should never write to the journal file the page that
  ** contains the database locks.  The following assert verifies
  ** that we do not. */
  assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );

  assert( pPager->journalHdr<=pPager->journalOff );
  CODEC2(pPager, pPg->pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
  cksum = pager_cksum(pPager, (u8*)pData2);

  /* Even if an IO or diskfull error occurs while journalling the
  ** page in the block above, set the need-sync flag for the page.
  ** Otherwise, when the transaction is rolled back, the logic in
  ** playback_one_page() will think that the page needs to be restored
  ** in the database file. And if an IO error occurs while doing so,
  ** then corruption may follow.
  */
  pPg->flags |= PGHDR_NEED_SYNC;

  rc = write32bits(pPager->jfd, iOff, pPg->pgno);
  if( rc!=SQLITE_OK ) return rc;
  rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4);
  if( rc!=SQLITE_OK ) return rc;
  rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum);
  if( rc!=SQLITE_OK ) return rc;

  IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, 
           pPager->journalOff, pPager->pageSize));
  PAGER_INCR(sqlite3_pager_writej_count);
  PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
       PAGERID(pPager), pPg->pgno, 
       ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));

  pPager->journalOff += 8 + pPager->pageSize;
  pPager->nRec++;
  assert( pPager->pInJournal!=0 );
  rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
  testcase( rc==SQLITE_NOMEM );
  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
  rc |= addToSavepointBitvecs(pPager, pPg->pgno);
  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
  return rc;
}

/*
** Mark a single data page as writeable. The page is written into the 
** main journal or sub-journal as required. If the page is written into
** one of the journals, the corresponding bit is set in the 
** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs
** of any open savepoints as appropriate.
*/
static int pager_write(PgHdr *pPg){
  Pager *pPager = pPg->pPager;
  int rc = SQLITE_OK;


  /* This routine is not called unless a write-transaction has already 
  ** been started. The journal file may or may not be open at this point.
  ** It is never called in the ERROR state.
  */
  assert( pPager->eState==PAGER_WRITER_LOCKED
       || pPager->eState==PAGER_WRITER_CACHEMOD
       || pPager->eState==PAGER_WRITER_DBMOD
  );
  assert( assert_pager_state(pPager) );
  assert( pPager->errCode==0 );
  assert( pPager->readOnly==0 );

  CHECK_PAGE(pPg);

  /* The journal file needs to be opened. Higher level routines have already
  ** obtained the necessary locks to begin the write-transaction, but the
  ** rollback journal might not yet be open. Open it now if this is the case.
  **
  ** This is done before calling sqlite3PcacheMakeDirty() on the page. 
................................................................................
  if( pPager->eState==PAGER_WRITER_LOCKED ){
    rc = pager_open_journal(pPager);
    if( rc!=SQLITE_OK ) return rc;
  }
  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
  assert( assert_pager_state(pPager) );

  /* Mark the page that is about to be modified as dirty. */


  sqlite3PcacheMakeDirty(pPg);








  /* If a rollback journal is in use, them make sure the page that is about
  ** to change is in the rollback journal, or if the page is a new page off
  ** then end of the file, make sure it is marked as PGHDR_NEED_SYNC.
  */

  assert( (pPager->pInJournal!=0) == isOpen(pPager->jfd) );
  if( pPager->pInJournal!=0                                      /* Journal open */
   && sqlite3BitvecTestNotNull(pPager->pInJournal, pPg->pgno)==0 /* pPg not in jrnl */
  ){
    assert( pagerUseWal(pPager)==0 );
    if( pPg->pgno<=pPager->dbOrigSize ){











































      rc = pagerAddPageToRollbackJournal(pPg);
      if( rc!=SQLITE_OK ){

        return rc;
      }
    }else{
      if( pPager->eState!=PAGER_WRITER_DBMOD ){
        pPg->flags |= PGHDR_NEED_SYNC;
      }
      PAGERTRACE(("APPEND %d page %d needSync=%d\n",
              PAGERID(pPager), pPg->pgno,
             ((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
    }
  }
  
  /* If the statement journal is open and the page is not in it,
  ** then write the page into the statement journal.


  */
  if( pPager->nSavepoint>0 && subjRequiresPage(pPg) ){
    rc = subjournalPage(pPg);
  }


  /* Update the database size and return. */

  if( pPager->dbSize<pPg->pgno ){
    pPager->dbSize = pPg->pgno;
  }
  return rc;
}

/*

Changes to src/sqliteInt.h.

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# define sqlite3FaultSim(X) SQLITE_OK
#else
  int sqlite3FaultSim(int);
#endif

Bitvec *sqlite3BitvecCreate(u32);
int sqlite3BitvecTest(Bitvec*, u32);

int sqlite3BitvecSet(Bitvec*, u32);
void sqlite3BitvecClear(Bitvec*, u32, void*);
void sqlite3BitvecDestroy(Bitvec*);
u32 sqlite3BitvecSize(Bitvec*);
#ifndef SQLITE_OMIT_BUILTIN_TEST
int sqlite3BitvecBuiltinTest(int,int*);
#endif







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# define sqlite3FaultSim(X) SQLITE_OK
#else
  int sqlite3FaultSim(int);
#endif

Bitvec *sqlite3BitvecCreate(u32);
int sqlite3BitvecTest(Bitvec*, u32);
int sqlite3BitvecTestNotNull(Bitvec*, u32);
int sqlite3BitvecSet(Bitvec*, u32);
void sqlite3BitvecClear(Bitvec*, u32, void*);
void sqlite3BitvecDestroy(Bitvec*);
u32 sqlite3BitvecSize(Bitvec*);
#ifndef SQLITE_OMIT_BUILTIN_TEST
int sqlite3BitvecBuiltinTest(int,int*);
#endif