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 1.543 2008/11/27 02:22:11 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"

  assert( cbrk>=cellOffset+2*nCell );
  put2byte(&data[hdr+5], cbrk);
  data[hdr+1] = 0;
  data[hdr+2] = 0;
  data[hdr+7] = 0;
  addr = cellOffset+2*nCell;
  memset(&data[addr], 0, cbrk-addr);
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  if( cbrk-addr!=pPage->nFree ){
    return SQLITE_CORRUPT_BKPT;
  }
  return SQLITE_OK;
}

/*

  if( nFrag>=60 || cellOffset + 2*nCell > top - nByte ){
    defragmentPage(pPage);
    top = get2byte(&data[hdr+5]);
  }
  top -= nByte;
  assert( cellOffset + 2*nCell <= top );
  put2byte(&data[hdr+5], top);
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  return top;
}

/*
** Return a section of the pPage->aData to the freelist.
** The first byte of the new free block is pPage->aDisk[start]
** and the size of the block is "size" bytes.

  if( data[hdr+1]==data[hdr+5] && data[hdr+2]==data[hdr+6] ){
    int top;
    pbegin = get2byte(&data[hdr+1]);
    memcpy(&data[hdr+1], &data[pbegin], 2);
    top = get2byte(&data[hdr+5]);
    put2byte(&data[hdr+5], top + get2byte(&data[pbegin+2]));
  }
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  return SQLITE_OK;
}

/*
** Decode the flags byte (the first byte of the header) for a page
** and initialize fields of the MemPage structure accordingly.
**

**                   page pointed to by one of the cells on pPage.
**
** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
**                   overflow page in the list.
*/
static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  if( eType==PTRMAP_OVERFLOW2 ){
    /* The pointer is always the first 4 bytes of the page in this case.  */
    if( get4byte(pPage->aData)!=iFrom ){
      return SQLITE_CORRUPT_BKPT;
    }
    put4byte(pPage->aData, iTo);
  }else{

            goto end_allocate_page;
          }
          memcpy(&pNewTrunk->aData[0], &pTrunk->aData[0], 4);
          put4byte(&pNewTrunk->aData[4], k-1);
          memcpy(&pNewTrunk->aData[8], &pTrunk->aData[12], (k-1)*4);
          releasePage(pNewTrunk);
          if( !pPrevTrunk ){
            assert( sqlite3PagerIswriteable(pPage1->pDbPage) );
            put4byte(&pPage1->aData[32], iNewTrunk);
          }else{
            rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
            if( rc ){
              goto end_allocate_page;
            }
            put4byte(&pPrevTrunk->aData[0], iNewTrunk);

          TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d"
                 ": %d more free pages\n",
                 *pPgno, closest+1, k, pTrunk->pgno, n-1));
          if( closest<k-1 ){
            memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
          }
          put4byte(&aData[4], k-1);
          assert( sqlite3PagerIswriteable(pTrunk->pDbPage) );
          rc = sqlite3BtreeGetPage(pBt, *pPgno, ppPage, 1);
          if( rc==SQLITE_OK ){
            sqlite3PagerDontRollback((*ppPage)->pDbPage);
            rc = sqlite3PagerWrite((*ppPage)->pDbPage);
            if( rc!=SQLITE_OK ){
              releasePage(*ppPage);
            }

  BtShared *pBt = pPage->pBt;
  Pgno pgnoOvfl = 0;
  int nHeader;
  CellInfo info;

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );

  /* pPage is not necessarily writeable since pCell might be auxiliary
  ** buffer space that is separate from the pPage buffer area */
  assert( pCell<pPage->aData || pCell>=&pPage->aData[pBt->pageSize]
            || sqlite3PagerIswriteable(pPage->pDbPage) );

  /* Fill in the header. */
  nHeader = 0;
  if( !pPage->leaf ){
    nHeader += 4;
  }
  if( pPage->hasData ){
    nHeader += putVarint(&pCell[nHeader], nData+nZero);

        }
      }
#endif
      if( rc ){
        releasePage(pToRelease);
        return rc;
      }

      /* If pToRelease is not zero than pPrior points into the data area
      ** of pToRelease.  Make sure pToRelease is still writeable. */
      assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );

      /* If pPrior is part of the data area of pPage, then make sure pPage
      ** is still writeable */
      assert( pPrior<pPage->aData || pPrior>=&pPage->aData[pBt->pageSize]
            || sqlite3PagerIswriteable(pPage->pDbPage) );

      put4byte(pPrior, pgnoOvfl);
      releasePage(pToRelease);
      pToRelease = pOvfl;
      pPrior = pOvfl->aData;
      put4byte(pPrior, 0);
      pPayload = &pOvfl->aData[4];
      spaceLeft = pBt->usableSize - 4;
    }
    n = nPayload;
    if( n>spaceLeft ) n = spaceLeft;

    /* If pToRelease is not zero than pPayload points into the data area
    ** of pToRelease.  Make sure pToRelease is still writeable. */
    assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );

    /* If pPayload is part of the data area of pPage, then make sure pPage
    ** is still writeable */
    assert( pPayload<pPage->aData || pPayload>=&pPage->aData[pBt->pageSize]
            || sqlite3PagerIswriteable(pPage->pDbPage) );

    if( nSrc>0 ){
      if( n>nSrc ) n = nSrc;
      assert( pSrc );
      memcpy(pPayload, pSrc, n);
    }else{
      memset(pPayload, 0, n);
    }

  assert( idx>=0 && idx<pPage->nCell );
  assert( sz==cellSize(pPage, idx) );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  data = pPage->aData;
  ptr = &data[pPage->cellOffset + 2*idx];
  pc = get2byte(ptr);
  if( (pc<pPage->hdrOffset+6+(pPage->leaf?0:4))
     || (pc+sz>pPage->pBt->usableSize) ){
    return SQLITE_CORRUPT_BKPT;
  }
  rc = freeSpace(pPage, pc, sz);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  for(i=idx+1; i<pPage->nCell; i++, ptr+=2){

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  totalSize = 0;
  for(i=0; i<nCell; i++){
    totalSize += aSize[i];
  }
  assert( totalSize+2*nCell<=pPage->nFree );
  assert( pPage->nCell==0 );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  cellptr = pPage->cellOffset;
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  put2byte(&data[hdr+3], nCell);
  if( nCell ){
    cellbody = allocateSpace(pPage, totalSize);
    assert( cellbody>0 );

  /* Allocate a new page. Insert the overflow cell from pPage
  ** into it. Then remove the overflow cell from pPage.
  */
  rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
  if( rc==SQLITE_OK ){
    pCell = pPage->aOvfl[0].pCell;
    szCell = cellSizePtr(pPage, pCell);
    assert( sqlite3PagerIswriteable(pNew->pDbPage) );
    zeroPage(pNew, pPage->aData[0]);
    assemblePage(pNew, 1, &pCell, &szCell);
    pPage->nOverflow = 0;
  
    /* pPage is currently the right-child of pParent. Change this
    ** so that the right-child is the new page allocated above and
    ** pPage is the next-to-right child. 

        }
      }
      iSpace2 += sz;
      assert( sz<=pBt->pageSize/4 );
      assert( iSpace2<=pBt->pageSize );
      rc = insertCell(pParent, nxDiv, pCell, sz, pTemp, 4);
      if( rc!=SQLITE_OK ) goto balance_cleanup;
      assert( sqlite3PagerIswriteable(pParent->pDbPage) );
      put4byte(findOverflowCell(pParent,nxDiv), pNew->pgno);

      /* If this is an auto-vacuum database, and not a leaf-data tree,
      ** then update the pointer map with an entry for the overflow page
      ** that the cell just inserted points to (if any).
      */
      if( ISAUTOVACUUM && !leafData ){

    if( ISAUTOVACUUM ){
      rc = ptrmapPut(pBt, get4byte(zChild), PTRMAP_BTREE, apNew[nNew-1]->pgno);
      if( rc!=SQLITE_OK ){
        goto balance_cleanup;
      }
    }
  }
  assert( sqlite3PagerIswriteable(pParent->pDbPage) );
  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]);

        zeroPage(pPage, pChild->aData[0]);
        for(i=0; i<pChild->nCell; i++){
          apCell[i] = findCell(pChild,i);
          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]));
        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. */

  assert( pCur->iPage==0 );
  assert( pCur->apPage[0]->nOverflow>0 );

  VVA_ONLY( pCur->pagesShuffled = 1 );
  pPage = pCur->apPage[0];
  pBt = pPage->pBt;
  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  rc = allocateBtreePage(pBt, &pChild, &pgnoChild, pPage->pgno, 0);
  if( rc ) return rc;
  assert( sqlite3PagerIswriteable(pChild->pDbPage) );
  usableSize = pBt->usableSize;
  data = pPage->aData;
  hdr = pPage->hdrOffset;
  cbrk = get2byte(&data[hdr+5]);

    int nCopy = pPage->nOverflow*sizeof(pPage->aOvfl[0]);
    memcpy(pChild->aOvfl, pPage->aOvfl, nCopy);
    pChild->nOverflow = pPage->nOverflow;
    if( pChild->nOverflow ){
      pChild->nFree = 0;
    }
    assert( pChild->nCell==pPage->nCell );
    assert( sqlite3PagerIswriteable(pPage->pDbPage) );
    zeroPage(pPage, pChild->aData[0] & ~PTF_LEAF);
    put4byte(&pPage->aData[pPage->hdrOffset+8], pgnoChild);
    TRACE(("BALANCE: copy root %d into %d\n", pPage->pgno, pChild->pgno));
    if( ISAUTOVACUUM ){
      rc = ptrmapPut(pBt, pChild->pgno, PTRMAP_BTREE, pPage->pgno);
#ifndef SQLITE_OMIT_AUTOVACUUM
      if( rc==SQLITE_OK ){

        */
        testcase( pPage->nFree==pBt->usableSize*2/3+1 );
        testcase( pLeafPage->nFree+2+szNext==pBt->usableSize*2/3+1 );
        leafCursorInvalid = 1;
      }        

      if( rc==SQLITE_OK ){
        assert( sqlite3PagerIswriteable(pPage->pDbPage) );
        put4byte(findOverflowCell(pPage, idx), pgnoChild);
        VVA_ONLY( pCur->pagesShuffled = 0 );
        rc = balance(pCur, 0);
      }

      if( rc==SQLITE_OK && leafCursorInvalid ){
        /* The leaf-node is now underfull and so the tree needs to be 

# 2007 March 24
#
# 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.
#
#***********************************************************************
# This file implements regression tests for SQLite library.
#
# $Id: exclusive2.test,v 1.10 2008/11/27 02:22:11 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

ifcapable {!pager_pragmas} {
  finish_test
  return

#
# As above, this test is only applicable if the pager cache is
# large enough to hold the entire database. With 1024 byte pages,
# this means 19 pages.  We also need to disable the soft-heap-limit
# to prevent memory-induced cache spills.
#
do_test exclusive2-2.1 {
  execsql {PRAGMA cache_size=1000;}
  execsql {PRAGMA locking_mode = exclusive;}
  execsql {
    BEGIN;
    DELETE FROM t1;
    INSERT INTO t1(a) VALUES(randstr(10, 400));
    INSERT INTO t1(a) VALUES(randstr(10, 400));
    INSERT INTO t1(a) SELECT randstr(10, 400) FROM t1;