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 1.490 2008/07/19 11:49:07 danielk1977 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 SQLITE_OK;
}

/*
** Change the MemPage.pParent pointer on the page whose number is
** given in the second argument so that MemPage.pParent holds the
** pointer in the third argument.
**
** If the final argument, updatePtrmap, is non-zero and the database
** is an auto-vacuum database, then the pointer-map entry for pgno
** is updated.
*/
static int reparentPage(
  BtShared *pBt,                /* B-Tree structure */
  Pgno pgno,                    /* Page number of child being adopted */
  MemPage *pNewParent,          /* New parent of pgno */
  int idx,                      /* Index of child page pgno in pNewParent */
  int updatePtrmap              /* If true, update pointer-map for pgno */
){
  MemPage *pThis;
  DbPage *pDbPage;

  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( pNewParent!=0 );
  if( pgno==0 ) return SQLITE_OK;
  assert( pBt->pPager!=0 );

      }
      pThis->idxParent = idx;
    }
    sqlite3PagerUnref(pDbPage);
  }

#ifndef SQLITE_OMIT_AUTOVACUUM
  if( pBt->autoVacuum && updatePtrmap ){
    return ptrmapPut(pBt, pgno, PTRMAP_BTREE, pNewParent->pgno);
  }

#ifndef NDEBUG
  /* If the updatePtrmap flag was clear, assert that the entry in the
  ** pointer-map is already correct.
  */
  if( pBt->autoVacuum ){
    u8 eType;
    Pgno ii;
    ptrmapGet(pBt, pgno, &eType, &ii);
    assert( ii==pNewParent->pgno && eType==PTRMAP_BTREE );
  }
#endif

#endif
  return SQLITE_OK;
}



/*
** Change the pParent pointer of all children of pPage to point back
** to pPage.
**
** In other words, for every child of pPage, invoke reparentPage()
** to make sure that each child knows that pPage is its parent.
**
** This routine gets called after you memcpy() one page into
** another.
**
** If updatePtrmap is true, then the pointer-map entries for all child
** pages of pPage are updated.
*/
static int reparentChildPages(MemPage *pPage, int updatePtrmap){


  int rc = SQLITE_OK;

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  if( !pPage->leaf ){
    int i;
    BtShared *pBt = pPage->pBt;
    Pgno iRight = get4byte(&pPage->aData[pPage->hdrOffset+8]);

    for(i=0; i<pPage->nCell; i++){
      u8 *pCell = findCell(pPage, i);
      rc = reparentPage(pBt, get4byte(pCell), pPage, i, updatePtrmap);
      if( rc!=SQLITE_OK ) return rc;
    }
    rc = reparentPage(pBt, iRight, pPage, i, updatePtrmap);

    pPage->idxShift = 0;
  }
  return rc;
}

/*
** Remove the i-th cell from pPage.  This routine effects pPage only.
** The cell content is not freed or deallocated.  It is assumed that
** the cell content has been copied someplace else.  This routine just

    assert( j<nMaxCells );
    assert( pNew->pgno==pgnoNew[i] );
    zeroPage(pNew, pageFlags);
    assemblePage(pNew, cntNew[i]-j, &apCell[j], &szCell[j]);
    assert( pNew->nCell>0 || (nNew==1 && cntNew[0]==0) );
    assert( pNew->nOverflow==0 );


    /* If this is an auto-vacuum database, update the pointer map entries
    ** that point to the siblings that were rearranged. These can be: left
    ** children of cells, the right-child of the page, or overflow pages
    ** pointed to by cells.
    */
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum ){
      for(k=j; k<cntNew[i]; k++){
        assert( k<nMaxCells );
        if( aFrom[k]==0xFF || apCopy[aFrom[k]]->pgno!=pNew->pgno ){
          rc = ptrmapPutOvfl(pNew, k-j);
          if( rc==SQLITE_OK && leafCorrection==0 ){
            rc = ptrmapPut(pBt, get4byte(apCell[k]), PTRMAP_BTREE, pNew->pgno);
          }
          if( rc!=SQLITE_OK ){
            goto balance_cleanup;
          }
        }
      }
    }
#endif

      assert( j<nMaxCells );
      pCell = apCell[j];
      sz = szCell[j] + leafCorrection;
      pTemp = &aSpace2[iSpace2];
      if( !pNew->leaf ){
        memcpy(&pNew->aData[8], pCell, 4);
#ifndef SQLITE_OMIT_AUTOVACUUM
        if( pBt->autoVacuum 
         && (aFrom[j]==0xFF || apCopy[aFrom[j]]->pgno!=pNew->pgno)
        ){
          rc = ptrmapPut(pBt, get4byte(pCell), PTRMAP_BTREE, pNew->pgno);
          if( rc!=SQLITE_OK ){
            goto balance_cleanup;
          }
        }
#endif
      }else if( leafData ){
        /* If the tree is a leaf-data tree, and the siblings are leaves, 
        ** then there is no divider cell in apCell[]. Instead, the divider 
        ** cell consists of the integer key for the right-most cell of 
        ** the sibling-page assembled above only.
        */
        CellInfo info;

          goto balance_cleanup;
        }
      }
#endif
      j++;
      nxDiv++;
    }

#ifndef SQLITE_OMIT_AUTOVACUUM
    /* Set the pointer-map entry for the new sibling page. */
    if( pBt->autoVacuum ){
      rc = ptrmapPut(pBt, pNew->pgno, PTRMAP_BTREE, pParent->pgno);
      if( rc!=SQLITE_OK ){
        goto balance_cleanup;
      }
    }
#endif
  }
  assert( j==nCell );
  assert( nOld>0 );
  assert( nNew>0 );
  if( (pageFlags & PTF_LEAF)==0 ){
    u8 *zChild = &apCopy[nOld-1]->aData[8];
    memcpy(&apNew[nNew-1]->aData[8], zChild, 4);
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum ){
      rc = ptrmapPut(pBt, get4byte(zChild), PTRMAP_BTREE, apNew[nNew-1]->pgno);
      if( rc!=SQLITE_OK ){
        goto balance_cleanup;
      }
    }
#endif
  }
  if( nxDiv==pParent->nCell+pParent->nOverflow ){
    /* Right-most sibling is the right-most child of pParent */
    put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew[nNew-1]);
  }else{
    /* Right-most sibling is the left child of the first entry in pParent
    ** past the right-most divider entry */
    put4byte(findOverflowCell(pParent, nxDiv), pgnoNew[nNew-1]);
  }

  /*
  ** Reparent children of all cells.
  */
  for(i=0; i<nNew; i++){
    rc = reparentChildPages(apNew[i], 0);
    if( rc!=SQLITE_OK ) goto balance_cleanup;
  }
  rc = reparentChildPages(pParent, 0);
  if( rc!=SQLITE_OK ) goto balance_cleanup;

  /*
  ** Balance the parent page.  Note that the current page (pPage) might
  ** have been added to the freelist so it might no longer be initialized.
  ** But the parent page will always be initialized.
  */

      pPage->pParent = 0;
      rc = sqlite3BtreeInitPage(pPage, 0);
      assert( rc==SQLITE_OK );
      freePage(pChild);
      TRACE(("BALANCE: transfer child %d into root %d\n",
              pChild->pgno, pPage->pgno));
    }
    rc = reparentChildPages(pPage, 1);
    assert( pPage->nOverflow==0 );
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( pBt->autoVacuum ){
      int i;
      for(i=0; i<pPage->nCell; i++){ 
        rc = ptrmapPutOvfl(pPage, i);
        if( rc!=SQLITE_OK ){

    if( rc ) goto balancedeeper_out;
    for(i=0; i<pChild->nCell; i++){
      rc = ptrmapPutOvfl(pChild, i);
      if( rc!=SQLITE_OK ){
        goto balancedeeper_out;
      }
    }
    rc = reparentChildPages(pChild, 1);
  }
#endif
  if( rc==SQLITE_OK ){
    rc = balance_nonroot(pChild);
  }

balancedeeper_out:
  releasePage(pChild);
  return rc;
}

/*