backup.c

sqlite最新源码

      p->bDestLocked = 1;
      rc = sqlite3BtreeGetMeta(p->pDest, 1, &p->iDestSchema);
    }

    /* If there is no open read-transaction on the source database, open
    ** one now. If a transaction is opened here, then it will be closed
    ** before this function exits.
    */
    if( rc==SQLITE_OK && 0==sqlite3BtreeIsInReadTrans(p->pSrc) ){
      rc = sqlite3BtreeBeginTrans(p->pSrc, 0);
      bCloseTrans = 1;
    }
  
    /* Now that there is a read-lock on the source database, query the
    ** source pager for the number of pages in the database.
    */
    if( rc==SQLITE_OK ){
      rc = sqlite3PagerPagecount(pSrcPager, &nSrcPage);
    }
    for(ii=0; (nPage<0 || ii<nPage) && p->iNext<=(Pgno)nSrcPage && !rc; ii++){
      const Pgno iSrcPg = p->iNext;                 /* Source page number */
      if( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) ){
        DbPage *pSrcPg;                             /* Source page object */
        rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg);
        if( rc==SQLITE_OK ){
          rc = backupOnePage(p, iSrcPg, sqlite3PagerGetData(pSrcPg));
          sqlite3PagerUnref(pSrcPg);
        }
      }
      p->iNext++;
    }
    if( rc==SQLITE_OK ){
      p->nPagecount = nSrcPage;
      p->nRemaining = nSrcPage+1-p->iNext;
      if( p->iNext>(Pgno)nSrcPage ){
        rc = SQLITE_DONE;
      }
    }
  
    if( rc==SQLITE_DONE ){
      const int nSrcPagesize = sqlite3BtreeGetPageSize(p->pSrc);
      const int nDestPagesize = sqlite3BtreeGetPageSize(p->pDest);
      int nDestTruncate;
  
      /* Update the schema version field in the destination database. This
      ** is to make sure that the schema-version really does change in
      ** the case where the source and destination databases have the
      ** same schema version.
      */
      sqlite3BtreeUpdateMeta(p->pDest, 1, p->iDestSchema+1);
      if( p->pDestDb ){
        sqlite3ResetInternalSchema(p->pDestDb, 0);
      }

      /* Set nDestTruncate to the final number of pages in the destination
      ** database. The complication here is that the destination page
      ** size may be different to the source page size. 
      **
      ** If the source page size is smaller than the destination page size, 
      ** round up. In this case the call to sqlite3OsTruncate() below will
      ** fix the size of the file. However it is important to call
      ** sqlite3PagerTruncateImage() here so that any pages in the 
      ** destination file that lie beyond the nDestTruncate page mark are
      ** journalled by PagerCommitPhaseOne() before they are destroyed
      ** by the file truncation.
      */
      if( nSrcPagesize<nDestPagesize ){
        int ratio = nDestPagesize/nSrcPagesize;
        nDestTruncate = (nSrcPage+ratio-1)/ratio;
        if( nDestTruncate==(int)PENDING_BYTE_PAGE(p->pDest->pBt) ){
          nDestTruncate--;
        }
      }else{
        nDestTruncate = nSrcPage * (nSrcPagesize/nDestPagesize);
      }
      sqlite3PagerTruncateImage(pDestPager, nDestTruncate);

      if( nSrcPagesize<nDestPagesize ){
        /* If the source page-size is smaller than the destination page-size,
        ** two extra things may need to happen:
        **
        **   * The destination may need to be truncated, and
        **
        **   * Data stored on the pages immediately following the 
        **     pending-byte page in the source database may need to be
        **     copied into the destination database.
        */
        const i64 iSize = (i64)nSrcPagesize * (i64)nSrcPage;
        sqlite3_file * const pFile = sqlite3PagerFile(pDestPager);

        assert( pFile );
        assert( (i64)nDestTruncate*(i64)nDestPagesize >= iSize || (
              nDestTruncate==(int)(PENDING_BYTE_PAGE(p->pDest->pBt)-1)
           && iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+nDestPagesize
        ));
        if( SQLITE_OK==(rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 1))
         && SQLITE_OK==(rc = backupTruncateFile(pFile, iSize))
         && SQLITE_OK==(rc = sqlite3PagerSync(pDestPager))
        ){
          i64 iOff;
          i64 iEnd = MIN(PENDING_BYTE + nDestPagesize, iSize);
          for(
            iOff=PENDING_BYTE+nSrcPagesize; 
            rc==SQLITE_OK && iOff<iEnd; 
            iOff+=nSrcPagesize
          ){
            PgHdr *pSrcPg = 0;
            const Pgno iSrcPg = (Pgno)((iOff/nSrcPagesize)+1);
            rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg);
            if( rc==SQLITE_OK ){
              u8 *zData = sqlite3PagerGetData(pSrcPg);
              rc = sqlite3OsWrite(pFile, zData, nSrcPagesize, iOff);
            }
            sqlite3PagerUnref(pSrcPg);
          }
        }
      }else{
        rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 0);
      }
  
      /* Finish committing the transaction to the destination database. */
      if( SQLITE_OK==rc
       && SQLITE_OK==(rc = sqlite3BtreeCommitPhaseTwo(p->pDest))
      ){
        rc = SQLITE_DONE;
      }
    }
  
    /* If bCloseTrans is true, then this function opened a read transaction
    ** on the source database. Close the read transaction here. There is
    ** no need to check the return values of the btree methods here, as
    ** "committing" a read-only transaction cannot fail.
    */
    if( bCloseTrans ){
      TESTONLY( int rc2 );
      TESTONLY( rc2  = ) sqlite3BtreeCommitPhaseOne(p->pSrc, 0);
      TESTONLY( rc2 |= ) sqlite3BtreeCommitPhaseTwo(p->pSrc);
      assert( rc2==SQLITE_OK );
    }
  
    p->rc = rc;
  }
  if( p->pDestDb ){
    sqlite3_mutex_leave(p->pDestDb->mutex);
  }
  sqlite3BtreeLeave(p->pSrc);
  sqlite3_mutex_leave(p->pSrcDb->mutex);
  return rc;
}

/*
** Release all resources associated with an sqlite3_backup* handle.
*/
int sqlite3_backup_finish(sqlite3_backup *p){
  sqlite3_backup **pp;                 /* Ptr to head of pagers backup list */
  sqlite3_mutex *mutex;                /* Mutex to protect source database */
  int rc;                              /* Value to return */

  /* Enter the mutexes */
  sqlite3_mutex_enter(p->pSrcDb->mutex);
  sqlite3BtreeEnter(p->pSrc);
  mutex = p->pSrcDb->mutex;
  if( p->pDestDb ){
    sqlite3_mutex_enter(p->pDestDb->mutex);
  }

  /* Detach this backup from the source pager. */
  if( p->pDestDb ){
    pp = sqlite3PagerBackupPtr(sqlite3BtreePager(p->pSrc));
    while( *pp!=p ){
      pp = &(*pp)->pNext;
    }
    *pp = p->pNext;
    p->pSrc->nBackup--;
  }

  /* If a transaction is still open on the Btree, roll it back. */
  sqlite3BtreeRollback(p->pDest);

  /* Set the error code of the destination database handle. */
  rc = (p->rc==SQLITE_DONE) ? SQLITE_OK : p->rc;
  sqlite3Error(p->pDestDb, rc, 0);

  /* Exit the mutexes and free the backup context structure. */
  if( p->pDestDb ){
    sqlite3_mutex_leave(p->pDestDb->mutex);
  }
  sqlite3BtreeLeave(p->pSrc);
  if( p->pDestDb ){
    sqlite3_free(p);
  }
  sqlite3_mutex_leave(mutex);
  return rc;
}

/*
** Return the number of pages still to be backed up as of the most recent
** call to sqlite3_backup_step().
*/
int sqlite3_backup_remaining(sqlite3_backup *p){
  return p->nRemaining;
}

/*
** Return the total number of pages in the source database as of the most 
** recent call to sqlite3_backup_step().
*/
int sqlite3_backup_pagecount(sqlite3_backup *p){
  return p->nPagecount;
}

/*
** This function is called after the contents of page iPage of the
** source database have been modified. If page iPage has already been 
** copied into the destination database, then the data written to the
** destination is now invalidated. The destination copy of iPage needs
** to be updated with the new data before the backup operation is
** complete.
**
** It is assumed that the mutex associated with the BtShared object
** corresponding to the source database is held when this function is
** called.
*/
void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
  sqlite3_backup *p;                   /* Iterator variable */
  for(p=pBackup; p; p=p->pNext){
    assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
    if( !isFatalError(p->rc) && iPage<p->iNext ){
      /* The backup process p has already copied page iPage. But now it
      ** has been modified by a transaction on the source pager. Copy
      ** the new data into the backup.
      */
      int rc = backupOnePage(p, iPage, aData);
      assert( rc!=SQLITE_BUSY && rc!=SQLITE_LOCKED );
      if( rc!=SQLITE_OK ){
        p->rc = rc;
      }
    }
  }
}

/*
** Restart the backup process. This is called when the pager layer
** detects that the database has been modified by an external database
** connection. In this case there is no way of knowing which of the
** pages that have been copied into the destination database are still 
** valid and which are not, so the entire process needs to be restarted.
**
** It is assumed that the mutex associated with the BtShared object
** corresponding to the source database is held when this function is
** called.
*/
void sqlite3BackupRestart(sqlite3_backup *pBackup){
  sqlite3_backup *p;                   /* Iterator variable */
  for(p=pBackup; p; p=p->pNext){
    assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
    p->iNext = 1;
  }
}

#ifndef SQLITE_OMIT_VACUUM
/*
** Copy the complete content of pBtFrom into pBtTo.  A transaction
** must be active for both files.
**
** The size of file pTo may be reduced by this operation. If anything 
** goes wrong, the transaction on pTo is rolled back. If successful, the 
** transaction is committed before returning.
*/
int sqlite3BtreeCopyFile(Btree *pTo, Btree *pFrom){
  int rc;
  sqlite3_backup b;
  sqlite3BtreeEnter(pTo);
  sqlite3BtreeEnter(pFrom);

  /* Set up an sqlite3_backup object. sqlite3_backup.pDestDb must be set
  ** to 0. This is used by the implementations of sqlite3_backup_step()
  ** and sqlite3_backup_finish() to detect that they are being called
  ** from this function, not directly by the user.
  */
  memset(&b, 0, sizeof(b));
  b.pSrcDb = pFrom->db;
  b.pSrc = pFrom;
  b.pDest = pTo;
  b.iNext = 1;

  /* 0x7FFFFFFF is the hard limit for the number of pages in a database
  ** file. By passing this as the number of pages to copy to
  ** sqlite3_backup_step(), we can guarantee that the copy finishes 
  ** within a single call (unless an error occurs). The assert() statement
  ** checks this assumption - (p->rc) should be set to either SQLITE_DONE 
  ** or an error code.
  */
  sqlite3_backup_step(&b, 0x7FFFFFFF);
  assert( b.rc!=SQLITE_OK );
  rc = sqlite3_backup_finish(&b);
  if( rc==SQLITE_OK ){
    pTo->pBt->pageSizeFixed = 0;
  }

  sqlite3BtreeLeave(pFrom);
  sqlite3BtreeLeave(pTo);
  return rc;
}
#endif /* SQLITE_OMIT_VACUUM */