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Overview
Comment:Optimizations to the BTree module for a modest speed improvement. (CVS 810)
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SHA1:39902a70417475225956704a037493515e9b08b9
User & Date: drh 2003-01-04 16:48:09
Context
2003-01-04
18:53
Another optimization to the btree logic. (CVS 811) check-in: 03d20673 user: drh tags: trunk
16:48
Optimizations to the BTree module for a modest speed improvement. (CVS 810) check-in: 39902a70 user: drh tags: trunk
2003-01-03
02:04
Allow the rollback journal to be empty except for its header. Ticket #212. (CVS 809) check-in: 1ba41bc2 user: drh 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 1.76 2003/01/02 14:43:56 drh 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.
................................................................................
** The pageDestructor() routine handles that chore.
*/
struct MemPage {
  union {
    char aDisk[SQLITE_PAGE_SIZE];  /* Page data stored on disk */
    PageHdr hdr;                   /* Overlay page header */
  } u;
  int isInit;                    /* True if auxiliary data is initialized */


  MemPage *pParent;              /* The parent of this page.  NULL for root */

  int nFree;                     /* Number of free bytes in u.aDisk[] */
  int nCell;                     /* Number of entries on this page */
  int isOverfull;                /* Some apCell[] points outside u.aDisk[] */
  Cell *apCell[MX_CELL+2];       /* All data entires in sorted order */
};

/*
** The in-memory image of a disk page has the auxiliary information appended
** to the end.  EXTRA_SIZE is the number of bytes of space needed to hold
** that extra information.
................................................................................
  MemPage *pNewPage;
  Btree *pBt = pCur->pBt;

  rc = sqlitepager_get(pBt->pPager, newPgno, (void**)&pNewPage);
  if( rc ) return rc;
  rc = initPage(pBt, pNewPage, newPgno, pCur->pPage);
  if( rc ) return rc;






  sqlitepager_unref(pCur->pPage);
  pCur->pPage = pNewPage;
  pCur->idx = 0;
  return SQLITE_OK;
}

/*
................................................................................
** to the page we are coming from.  If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
static int moveToParent(BtCursor *pCur){
  Pgno oldPgno;
  MemPage *pParent;
  int i;
  pParent = pCur->pPage->pParent;
  if( pParent==0 ) return SQLITE_INTERNAL;

  oldPgno = sqlitepager_pagenumber(pCur->pPage);
  sqlitepager_ref(pParent);
  sqlitepager_unref(pCur->pPage);
  pCur->pPage = pParent;





















  pCur->idx = pParent->nCell;
  oldPgno = SWAB32(pCur->pBt, oldPgno);
  for(i=0; i<pParent->nCell; i++){
    if( pParent->apCell[i]->h.leftChild==oldPgno ){
      pCur->idx = i;
      break;

    }
  }
  return SQLITE_OK;
}

/*
** Move the cursor to the root page
................................................................................
** finds the right-most entry beneath the *page*.
*/
static int moveToRightmost(BtCursor *pCur){
  Pgno pgno;
  int rc;

  while( (pgno = pCur->pPage->u.hdr.rightChild)!=0 ){

    rc = moveToChild(pCur, SWAB32(pCur->pBt, pgno));
    if( rc ) return rc;
  }
  pCur->idx = pCur->pPage->nCell - 1;
  return SQLITE_OK;
}

................................................................................
      chldPg = pPage->apCell[lwr]->h.leftChild;
    }
    if( chldPg==0 ){
      pCur->iMatch = c;
      if( pRes ) *pRes = c;
      return SQLITE_OK;
    }

    rc = moveToChild(pCur, SWAB32(pCur->pBt, chldPg));
    if( rc ) return rc;
  }
  /* NOT REACHED */
}

/*
................................................................................
}

/*
** 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.
*/
static void reparentPage(Pager *pPager, Pgno pgno, MemPage *pNewParent){
  MemPage *pThis;

  if( pgno==0 ) return;
  assert( pPager!=0 );
  pThis = sqlitepager_lookup(pPager, pgno);
  if( pThis && pThis->isInit ){
    if( pThis->pParent!=pNewParent ){
      if( pThis->pParent ) sqlitepager_unref(pThis->pParent);
      pThis->pParent = pNewParent;
      if( pNewParent ) sqlitepager_ref(pNewParent);
    }

    sqlitepager_unref(pThis);
  }
}

/*
** Reparent all children of the given page to be the given page.
** In other words, for every child of pPage, invoke reparentPage()
................................................................................
** This routine gets called after you memcpy() one page into
** another.
*/
static void reparentChildPages(Btree *pBt, MemPage *pPage){
  int i;
  Pager *pPager = pBt->pPager;
  for(i=0; i<pPage->nCell; i++){
    reparentPage(pPager, SWAB32(pBt, pPage->apCell[i]->h.leftChild), pPage);
  }
  reparentPage(pPager, SWAB32(pBt, pPage->u.hdr.rightChild), pPage);

}

/*
** 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
** removes the reference to the cell from pPage.
................................................................................
  assert( sz==cellSize(pBt, pPage->apCell[idx]) );
  assert( sqlitepager_iswriteable(pPage) );
  freeSpace(pBt, pPage, Addr(pPage->apCell[idx]) - Addr(pPage), sz);
  for(j=idx; j<pPage->nCell-1; j++){
    pPage->apCell[j] = pPage->apCell[j+1];
  }
  pPage->nCell--;

}

/*
** Insert a new cell on pPage at cell index "i".  pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there.  If it
................................................................................
  if( idx<=0 ){
    pPage->isOverfull = 1;
    pPage->apCell[i] = pCell;
  }else{
    memcpy(&pPage->u.aDisk[idx], pCell, sz);
    pPage->apCell[i] = (Cell*)&pPage->u.aDisk[idx];
  }

}

/*
** Rebuild the linked list of cells on a page so that the cells
** occur in the order specified by the pPage->apCell[] array.  
** Invoke this routine once to repair damage after one or more
** invocations of either insertCell() or dropCell().
................................................................................
    rc = sqlitepager_write(pPage);
    if( rc ) return rc;
    rc = allocatePage(pBt, &pChild, &pgnoChild, sqlitepager_pagenumber(pPage));
    if( rc ) return rc;
    assert( sqlitepager_iswriteable(pChild) );
    copyPage(pChild, pPage);
    pChild->pParent = pPage;

    sqlitepager_ref(pPage);
    pChild->isOverfull = 1;
    if( pCur && pCur->pPage==pPage ){
      sqlitepager_unref(pPage);
      pCur->pPage = pChild;
    }else{
      extraUnref = pChild;
................................................................................
      idx = i;
      break;
    }
  }
  if( idx<0 && pParent->u.hdr.rightChild==swabPgno ){
    idx = pParent->nCell;
  }
  if( idx<0 ){
    return SQLITE_CORRUPT;
  }

  /*
  ** Initialize variables so that it will be safe to jump
  ** directly to balance_cleanup at any moment.
  */
  nOld = nNew = 0;
  sqlitepager_ref(pParent);
................................................................................
    }else{
      break;
    }
    rc = sqlitepager_get(pBt->pPager, pgnoOld[i], (void**)&apOld[i]);
    if( rc ) goto balance_cleanup;
    rc = initPage(pBt, apOld[i], pgnoOld[i], pParent);
    if( rc ) goto balance_cleanup;

    nOld++;
  }

  /*
  ** Set iCur to be the index in apCell[] of the cell that the cursor
  ** is pointing to.  We will need this later on in order to keep the
  ** cursor pointing at the same cell.  If pCur points to a page that







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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 1.77 2003/01/04 16:48:09 drh 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.
................................................................................
** The pageDestructor() routine handles that chore.
*/
struct MemPage {
  union {
    char aDisk[SQLITE_PAGE_SIZE];  /* Page data stored on disk */
    PageHdr hdr;                   /* Overlay page header */
  } u;
  u8 isInit;                     /* True if auxiliary data is initialized */
  u8 idxShift;                   /* True if apCell[] indices have changed */
  u8 isOverfull;                 /* Some apCell[] points outside u.aDisk[] */
  MemPage *pParent;              /* The parent of this page.  NULL for root */
  int idxParent;                 /* Index in pParent->apCell[] of this node */
  int nFree;                     /* Number of free bytes in u.aDisk[] */
  int nCell;                     /* Number of entries on this page */

  Cell *apCell[MX_CELL+2];       /* All data entires in sorted order */
};

/*
** The in-memory image of a disk page has the auxiliary information appended
** to the end.  EXTRA_SIZE is the number of bytes of space needed to hold
** that extra information.
................................................................................
  MemPage *pNewPage;
  Btree *pBt = pCur->pBt;

  rc = sqlitepager_get(pBt->pPager, newPgno, (void**)&pNewPage);
  if( rc ) return rc;
  rc = initPage(pBt, pNewPage, newPgno, pCur->pPage);
  if( rc ) return rc;
  assert( pCur->idx>=pCur->pPage->nCell
          || pCur->pPage->apCell[pCur->idx]->h.leftChild==SWAB32(pBt,newPgno) );
  assert( pCur->idx<pCur->pPage->nCell
          || pCur->pPage->u.hdr.rightChild==SWAB32(pBt,newPgno) );
  pNewPage->idxParent = pCur->idx;
  pCur->pPage->idxShift = 0;
  sqlitepager_unref(pCur->pPage);
  pCur->pPage = pNewPage;
  pCur->idx = 0;
  return SQLITE_OK;
}

/*
................................................................................
** to the page we are coming from.  If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
static int moveToParent(BtCursor *pCur){
  Pgno oldPgno;
  MemPage *pParent;
  int idxParent;
  pParent = pCur->pPage->pParent;
  if( pParent==0 ) return SQLITE_INTERNAL;
  idxParent = pCur->pPage->idxParent;
  oldPgno = sqlitepager_pagenumber(pCur->pPage);
  sqlitepager_ref(pParent);
  sqlitepager_unref(pCur->pPage);
  pCur->pPage = pParent;
  assert( pParent->idxShift==0 );
  if( pParent->idxShift==0 ){
    pCur->idx = idxParent;
#ifndef NDEBUG  
    /* Verify that pCur->idx is the correct index to point back to the child
    ** page we just came from 
    */
    oldPgno = SWAB32(pCur->pBt, oldPgno);
    if( pCur->idx<pParent->nCell ){
      assert( pParent->apCell[idxParent]->h.leftChild==oldPgno );
    }else{
      assert( pParent->u.hdr.rightChild==oldPgno );
    }
#endif
  }else{
    /* The MemPage.idxShift flag indicates that cell indices might have 
    ** changed since idxParent was set and hence idxParent might be out
    ** of date.  So recompute the parent cell index by scanning all cells
    ** and locating the one that points to the child we just came from.
    */
    int i;
    pCur->idx = pParent->nCell;
    oldPgno = SWAB32(pCur->pBt, oldPgno);
    for(i=0; i<pParent->nCell; i++){
      if( pParent->apCell[i]->h.leftChild==oldPgno ){
        pCur->idx = i;
        break;
      }
    }
  }
  return SQLITE_OK;
}

/*
** Move the cursor to the root page
................................................................................
** finds the right-most entry beneath the *page*.
*/
static int moveToRightmost(BtCursor *pCur){
  Pgno pgno;
  int rc;

  while( (pgno = pCur->pPage->u.hdr.rightChild)!=0 ){
    pCur->idx = pCur->pPage->nCell;
    rc = moveToChild(pCur, SWAB32(pCur->pBt, pgno));
    if( rc ) return rc;
  }
  pCur->idx = pCur->pPage->nCell - 1;
  return SQLITE_OK;
}

................................................................................
      chldPg = pPage->apCell[lwr]->h.leftChild;
    }
    if( chldPg==0 ){
      pCur->iMatch = c;
      if( pRes ) *pRes = c;
      return SQLITE_OK;
    }
    pCur->idx = lwr;
    rc = moveToChild(pCur, SWAB32(pCur->pBt, chldPg));
    if( rc ) return rc;
  }
  /* NOT REACHED */
}

/*
................................................................................
}

/*
** 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.
*/
static void reparentPage(Pager *pPager, Pgno pgno, MemPage *pNewParent,int idx){
  MemPage *pThis;

  if( pgno==0 ) return;
  assert( pPager!=0 );
  pThis = sqlitepager_lookup(pPager, pgno);
  if( pThis && pThis->isInit ){
    if( pThis->pParent!=pNewParent ){
      if( pThis->pParent ) sqlitepager_unref(pThis->pParent);
      pThis->pParent = pNewParent;
      if( pNewParent ) sqlitepager_ref(pNewParent);
    }
    pThis->idxParent = idx;
    sqlitepager_unref(pThis);
  }
}

/*
** Reparent all children of the given page to be the given page.
** In other words, for every child of pPage, invoke reparentPage()
................................................................................
** This routine gets called after you memcpy() one page into
** another.
*/
static void reparentChildPages(Btree *pBt, MemPage *pPage){
  int i;
  Pager *pPager = pBt->pPager;
  for(i=0; i<pPage->nCell; i++){
    reparentPage(pPager, SWAB32(pBt, pPage->apCell[i]->h.leftChild), pPage, i);
  }
  reparentPage(pPager, SWAB32(pBt, pPage->u.hdr.rightChild), pPage, i);
  pPage->idxShift = 0;
}

/*
** 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
** removes the reference to the cell from pPage.
................................................................................
  assert( sz==cellSize(pBt, pPage->apCell[idx]) );
  assert( sqlitepager_iswriteable(pPage) );
  freeSpace(pBt, pPage, Addr(pPage->apCell[idx]) - Addr(pPage), sz);
  for(j=idx; j<pPage->nCell-1; j++){
    pPage->apCell[j] = pPage->apCell[j+1];
  }
  pPage->nCell--;
  pPage->idxShift = 1;
}

/*
** Insert a new cell on pPage at cell index "i".  pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there.  If it
................................................................................
  if( idx<=0 ){
    pPage->isOverfull = 1;
    pPage->apCell[i] = pCell;
  }else{
    memcpy(&pPage->u.aDisk[idx], pCell, sz);
    pPage->apCell[i] = (Cell*)&pPage->u.aDisk[idx];
  }
  pPage->idxShift = 1;
}

/*
** Rebuild the linked list of cells on a page so that the cells
** occur in the order specified by the pPage->apCell[] array.  
** Invoke this routine once to repair damage after one or more
** invocations of either insertCell() or dropCell().
................................................................................
    rc = sqlitepager_write(pPage);
    if( rc ) return rc;
    rc = allocatePage(pBt, &pChild, &pgnoChild, sqlitepager_pagenumber(pPage));
    if( rc ) return rc;
    assert( sqlitepager_iswriteable(pChild) );
    copyPage(pChild, pPage);
    pChild->pParent = pPage;
    pChild->idxParent = pChild->nCell;
    sqlitepager_ref(pPage);
    pChild->isOverfull = 1;
    if( pCur && pCur->pPage==pPage ){
      sqlitepager_unref(pPage);
      pCur->pPage = pChild;
    }else{
      extraUnref = pChild;
................................................................................
      idx = i;
      break;
    }
  }
  if( idx<0 && pParent->u.hdr.rightChild==swabPgno ){
    idx = pParent->nCell;
  }
  assert( idx>=0 );
  /* assert( pParent->idxShift || idx==pPage->idxParent ); */


  /*
  ** Initialize variables so that it will be safe to jump
  ** directly to balance_cleanup at any moment.
  */
  nOld = nNew = 0;
  sqlitepager_ref(pParent);
................................................................................
    }else{
      break;
    }
    rc = sqlitepager_get(pBt->pPager, pgnoOld[i], (void**)&apOld[i]);
    if( rc ) goto balance_cleanup;
    rc = initPage(pBt, apOld[i], pgnoOld[i], pParent);
    if( rc ) goto balance_cleanup;
    apOld[i]->idxParent = k;
    nOld++;
  }

  /*
  ** Set iCur to be the index in apCell[] of the cell that the cursor
  ** is pointing to.  We will need this later on in order to keep the
  ** cursor pointing at the same cell.  If pCur points to a page that

Changes to test/table.test.

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#    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.  The
# focus of this file is testing the CREATE TABLE statement.
#
# $Id: table.test,v 1.20 2002/08/31 18:53:09 drh Exp $

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

# Create a basic table and verify it is added to sqlite_master
#
do_test table-1.1 {
................................................................................

# Drop the even numbered tables
#
set r {}
for {set i 1} {$i<=100} {incr i 2} {
  lappend r [format test%03d $i]
}
#execsql {--vdbe-trace-on--}
do_test table-4.2 {
  for {set i 2} {$i<=100} {incr i 2} {

    set sql "DROP TABLE [format TEST%03d $i]"
    execsql $sql
  }
  execsql {SELECT name FROM sqlite_master WHERE type!='meta' ORDER BY name}
} $r
#exit








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#    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.  The
# focus of this file is testing the CREATE TABLE statement.
#
# $Id: table.test,v 1.21 2003/01/04 16:48:10 drh Exp $

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

# Create a basic table and verify it is added to sqlite_master
#
do_test table-1.1 {
................................................................................

# Drop the even numbered tables
#
set r {}
for {set i 1} {$i<=100} {incr i 2} {
  lappend r [format test%03d $i]
}

do_test table-4.2 {
  for {set i 2} {$i<=100} {incr i 2} {
    # if {$i==38} {execsql {pragma vdbe_trace=on}}
    set sql "DROP TABLE [format TEST%03d $i]"
    execsql $sql
  }
  execsql {SELECT name FROM sqlite_master WHERE type!='meta' ORDER BY name}
} $r
#exit