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Overview
Comment:Try to avoid reading pages when moving overflow chains to the free-list. (CVS 3886)
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SHA1:8cccec68bd9073b2b19d3d31cf0b77b0ce76172e
User & Date: danielk1977 2007-04-30 16:55:01
Context
2007-04-30
17:52
Lift docListMerge() call out of loadSegmentLeavesInt() for prefix search. Doclists from multiple prefix matches will need a union merge function, which will have to logically happen across a segment before doclists are merged between segments. (CVS 3887) check-in: 7ddb8266 user: shess tags: trunk
16:55
Try to avoid reading pages when moving overflow chains to the free-list. (CVS 3886) check-in: 8cccec68 user: danielk1977 tags: trunk
2007-04-28
15:47
Add some tests (and 2 resulting bug fixes) to incr vacuum mode. (CVS 3885) check-in: 89b1b3f8 user: danielk1977 tags: trunk
Changes
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Changes to src/btree.c.

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** 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.
**
*************************************************************************
** $Id: btree.c,v 1.361 2007/04/28 15:47:44 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
................................................................................
      }
      TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
    }
    releasePage(pTrunk);
  }
  return rc;
}























































/*
** Free any overflow pages associated with the given Cell.
*/
static int clearCell(MemPage *pPage, unsigned char *pCell){
  BtShared *pBt = pPage->pBt;
  CellInfo info;
................................................................................
  nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
  assert( ovflPgno==0 || nOvfl>0 );
  while( nOvfl-- ){
    MemPage *pOvfl;
    if( ovflPgno==0 || ovflPgno>sqlite3PagerPagecount(pBt->pPager) ){
      return SQLITE_CORRUPT_BKPT;
    }

    rc = getPage(pBt, ovflPgno, &pOvfl, nOvfl==0);
    if( rc ) return rc;
    if( nOvfl ){
      ovflPgno = get4byte(pOvfl->aData);
    }
    rc = freePage(pOvfl);
    sqlite3PagerUnref(pOvfl->pDbPage);
    if( rc ) return rc;
  }
  return SQLITE_OK;
}








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** 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.
**
*************************************************************************
** $Id: btree.c,v 1.362 2007/04/30 16:55:01 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
................................................................................
      }
      TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
    }
    releasePage(pTrunk);
  }
  return rc;
}

/*
** Get a MemPage structure for overflow page number ovfl. If it
** is not zero, the page number of the overflow page following the
** one retrieved is written to *pPgnoNext.
**
** If it is possible to figure out the page-number of the next
** overflow page without reading the data of page ovfl, then 
** sqlite3PagerAcquire() is passed the "noContent" flag when
** page ovfl is retrieved.
*/
static int getOverflowPage(
  BtShared *pBt, 
  Pgno ovfl, 
  MemPage **ppPage, 
  Pgno *pPgnoNext
){
  Pgno next = 0;
  int rc;

  if( !pPgnoNext ){
    return getPage(pBt, ovfl, ppPage, 1);
  }

#ifndef SQLITE_OMIT_AUTOVACUUM
  if( pBt->autoVacuum ){
    Pgno pgno;
    Pgno iGuess = ovfl+1;
    u8 eType;

    while( PTRMAP_ISPAGE(pBt, iGuess) || iGuess==PENDING_BYTE_PAGE(pBt) ){
      iGuess++;
    }

    if( iGuess<sqlite3PagerPagecount(pBt->pPager) ){
      rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
      if( rc!=SQLITE_OK ){
        return rc;
      }
      if( eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
        next = iGuess;
      }
    }
  }
#endif

  rc = getPage(pBt, ovfl, ppPage, 0);
  if( rc==SQLITE_OK ){
    assert(next==0 || next==get4byte((*ppPage)->aData));
    next = get4byte((*ppPage)->aData);
  }
  *pPgnoNext = next;
  return rc;
}

/*
** Free any overflow pages associated with the given Cell.
*/
static int clearCell(MemPage *pPage, unsigned char *pCell){
  BtShared *pBt = pPage->pBt;
  CellInfo info;
................................................................................
  nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
  assert( ovflPgno==0 || nOvfl>0 );
  while( nOvfl-- ){
    MemPage *pOvfl;
    if( ovflPgno==0 || ovflPgno>sqlite3PagerPagecount(pBt->pPager) ){
      return SQLITE_CORRUPT_BKPT;
    }

    rc = getOverflowPage(pBt, ovflPgno, &pOvfl, (nOvfl==0)?0:&ovflPgno);
    if( rc ) return rc;



    rc = freePage(pOvfl);
    sqlite3PagerUnref(pOvfl->pDbPage);
    if( rc ) return rc;
  }
  return SQLITE_OK;
}