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 1.677 2009/07/11 11:45:23 danielk1977 Exp $
** $Id: btree.c,v 1.678 2009/07/11 13:13:12 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"

      return rc;
    }
  }

  /* Save the positions of any other cursors open on this table before
  ** making any modifications. Make the page containing the entry to be 
  ** deleted writable. Then free any overflow pages associated with the 
  ** entry and finally remove the cell itself from within the page.  */
  if( SQLITE_OK!=(rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur))
   || SQLITE_OK!=(rc = sqlite3PagerWrite(pPage->pDbPage))
   || SQLITE_OK!=(rc = clearCell(pPage, pCell))
   || SQLITE_OK!=(rc = dropCell(pPage, iCellIdx, cellSizePtr(pPage, pCell)))
  ** entry and finally remove the cell itself from within the page.  
  */
  rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
  if( rc ) return rc;
  rc = sqlite3PagerWrite(pPage->pDbPage);
  if( rc ) return rc;
  rc = clearCell(pPage, pCell);
  if( rc ) return rc;
  rc = dropCell(pPage, iCellIdx, cellSizePtr(pPage, pCell));
  ){
    return rc;
  if( rc ) return rc;
  }

  /* If the cell deleted was not located on a leaf page, then the cursor
  ** is currently pointing to the largest entry in the sub-tree headed
  ** by the child-page of the cell that was just deleted from an internal
  ** node. The cell from the leaf node needs to be moved to the internal
  ** node to replace the deleted cell.  */
  if( !pPage->leaf ){
    MemPage *pLeaf = pCur->apPage[pCur->iPage];
    int nCell;
    Pgno n = pCur->apPage[iCellDepth+1]->pgno;
    unsigned char *pTmp;

    pCell = findCell(pLeaf, pLeaf->nCell-1);
    nCell = cellSizePtr(pLeaf, pCell);
    assert( MX_CELL_SIZE(pBt)>=nCell );

    allocateTempSpace(pBt);
    pTmp = pBt->pTmpSpace;

    if( SQLITE_OK!=(rc = sqlite3PagerWrite(pLeaf->pDbPage)) 
     || SQLITE_OK!=(rc = insertCell(pPage, iCellIdx, pCell-4, nCell+4, pTmp, n))
     || SQLITE_OK!=(rc = dropCell(pLeaf, pLeaf->nCell-1, nCell))
    rc = sqlite3PagerWrite(pLeaf->pDbPage);
    if( rc ) return rc;
    rc = insertCell(pPage, iCellIdx, pCell-4, nCell+4, pTmp, n);
    if( rc ) return rc;
    rc = dropCell(pLeaf, pLeaf->nCell-1, nCell);
    ){
      return rc;
    if( rc ) return rc;
    }
  }

  /* Balance the tree. If the entry deleted was located on a leaf page,
  ** then the cursor still points to that page. In this case the first
  ** call to balance() repairs the tree, and the if(...) condition is
  ** never true.
  **