SQLite

/*
** 2004 April 6
**
** 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.
**
*************************************************************************
** $Id: btree.c,v 1.544 2008/12/05 20:01:43 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

  sqlite3ScratchFree(apCell);
  for(i=0; i<nOld; i++){
    releasePage(apOld[i]);
  }
  for(i=0; i<nNew; i++){
    releasePage(apNew[i]);
  }
  pPage->nOverflow = 0;

  /* releasePage(pParent); */
  TRACE(("BALANCE: finished with %d: old=%d new=%d cells=%d\n",
          pPage->pgno, nOld, nNew, nCell));

  return rc;
}

          szCell[i] = cellSizePtr(pChild, apCell[i]);
        }
        assemblePage(pPage, pChild->nCell, apCell, szCell);
        /* Copy the right-pointer of the child to the parent. */
        assert( sqlite3PagerIswriteable(pPage->pDbPage) );
        put4byte(&pPage->aData[pPage->hdrOffset+8], 
            get4byte(&pChild->aData[pChild->hdrOffset+8]));
        rc = freePage(pChild);
        TRACE(("BALANCE: child %d transfer to page 1\n", pChild->pgno));
      }else{
        /* The child has more information that will fit on the root.
        ** The tree is already balanced.  Do nothing. */
        TRACE(("BALANCE: child %d will not fit on page 1\n", pChild->pgno));
      }
    }else{
      memcpy(pPage->aData, pChild->aData, pPage->pBt->usableSize);
      pPage->isInit = 0;
      rc = sqlite3BtreeInitPage(pPage);
      assert( rc==SQLITE_OK );
      freePage(pChild);
      TRACE(("BALANCE: transfer child %d into root %d\n",
              pChild->pgno, pPage->pgno));
    }
    assert( pPage->nOverflow==0 );
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( ISAUTOVACUUM && rc==SQLITE_OK ){
      rc = setChildPtrmaps(pPage);
    }
#endif
    releasePage(pChild);
  }
end_shallow_balance:
  sqlite3_free(apCell);

  MemPage *pPage = pCur->apPage[pCur->iPage];

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  if( pCur->iPage==0 ){
    rc = sqlite3PagerWrite(pPage->pDbPage);
    if( rc==SQLITE_OK && pPage->nOverflow>0 ){
      rc = balance_deeper(pCur);
      assert( pPage->nOverflow==0 || rc!=SQLITE_OK );
    }
    if( rc==SQLITE_OK && pPage->nCell==0 ){
      rc = balance_shallower(pCur);
      assert( pPage->nOverflow==0 || rc!=SQLITE_OK );
    }
  }else{
    if( pPage->nOverflow>0 || 
        (!isInsert && pPage->nFree>pPage->pBt->usableSize*2/3) ){
      rc = balance_nonroot(pCur);
      assert( pPage->nOverflow==0 || rc!=SQLITE_OK );
    }
  }
  return rc;
}

/*
** This routine checks all cursors that point to table pgnoRoot.

    idx = ++pCur->aiIdx[pCur->iPage];
    pCur->info.nSize = 0;
    pCur->validNKey = 0;
  }else{
    assert( pPage->leaf );
  }
  rc = insertCell(pPage, idx, newCell, szNew, 0, 0);
  if( rc==SQLITE_OK ){
  rc = balance(pCur, 1);
  }

  /* Must make sure nOverflow is reset to zero even if the balance()
  ** fails.  Internal data structure corruption will result otherwise. */
  assert( pPage->nOverflow==0 || rc!=SQLITE_OK );
  pPage->nOverflow = 0;

  if( rc==SQLITE_OK ){
    moveToRoot(pCur);
  }
end_insert:
  return rc;
}