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Overview
Comment:Avoid a performance problem when very large "VALUES(..), (..), (..)" terms are used in queries.
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Timelines: family | ancestors | descendants | both | recursive-selectdup
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SHA1: f5306ad6816cc377036685cdae227e762885229c
User & Date: dan 2017-02-03 19:16:39.919
Context
2017-02-03
20:54
Improved performance and stack usage when processing VALUES clauses with a very large number of rows. (check-in: 5706d4708a user: drh tags: trunk)
19:16
Avoid a performance problem when very large "VALUES(..), (..), (..)" terms are used in queries. (Closed-Leaf check-in: f5306ad681 user: dan tags: recursive-selectdup)
14:44
Modify the sqlite3SelectDup() routine to avoid recursing on Select.pPrior. (check-in: a7674ead5b user: dan tags: recursive-selectdup)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/select.c.
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      return SQLITE_ERROR;
    }
    assert( pTab->nTabRef==1 || ((pSel->selFlags&SF_Recursive) && pTab->nTabRef==2 ));

    pCte->zCteErr = "circular reference: %s";
    pSavedWith = pParse->pWith;
    pParse->pWith = pWith;







    sqlite3WalkSelect(pWalker, bMayRecursive ? pSel->pPrior : pSel);

    pParse->pWith = pWith;

    for(pLeft=pSel; pLeft->pPrior; pLeft=pLeft->pPrior);
    pEList = pLeft->pEList;
    if( pCte->pCols ){
      if( pEList && pEList->nExpr!=pCte->pCols->nExpr ){
        sqlite3ErrorMsg(pParse, "table %s has %d values for %d columns",








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      return SQLITE_ERROR;
    }
    assert( pTab->nTabRef==1 || ((pSel->selFlags&SF_Recursive) && pTab->nTabRef==2 ));

    pCte->zCteErr = "circular reference: %s";
    pSavedWith = pParse->pWith;
    pParse->pWith = pWith;
    if( bMayRecursive ){
      Select *pPrior = pSel->pPrior;
      assert( pPrior->pWith==0 );
      pPrior->pWith = pSel->pWith;
      sqlite3WalkSelect(pWalker, pPrior);
      pPrior->pWith = 0;
    }else{
      sqlite3WalkSelect(pWalker, pSel);
    }
    pParse->pWith = pWith;

    for(pLeft=pSel; pLeft->pPrior; pLeft=pLeft->pPrior);
    pEList = pLeft->pEList;
    if( pCte->pCols ){
      if( pEList && pEList->nExpr!=pCte->pCols->nExpr ){
        sqlite3ErrorMsg(pParse, "table %s has %d values for %d columns",
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**
** This function is used as the xSelectCallback2() callback by
** sqlite3SelectExpand() when walking a SELECT tree to resolve table
** names and other FROM clause elements. 
*/
static void selectPopWith(Walker *pWalker, Select *p){
  Parse *pParse = pWalker->pParse;

  With *pWith = findRightmost(p)->pWith;
  if( pWith!=0 ){
    assert( pParse->pWith==pWith );
    pParse->pWith = pWith->pOuter;

  }
}
#else
#define selectPopWith 0
#endif

/*








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**
** This function is used as the xSelectCallback2() callback by
** sqlite3SelectExpand() when walking a SELECT tree to resolve table
** names and other FROM clause elements. 
*/
static void selectPopWith(Walker *pWalker, Select *p){
  Parse *pParse = pWalker->pParse;
  if( pParse->pWith && p->pPrior==0 ){
    With *pWith = findRightmost(p)->pWith;
    if( pWith!=0 ){
      assert( pParse->pWith==pWith );
      pParse->pWith = pWith->pOuter;
    }
  }
}
#else
#define selectPopWith 0
#endif

/*
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    return WRC_Abort;
  }
  if( NEVER(p->pSrc==0) || (selFlags & SF_Expanded)!=0 ){
    return WRC_Prune;
  }
  pTabList = p->pSrc;
  pEList = p->pEList;
  if( pWalker->xSelectCallback2==selectPopWith ){
    sqlite3WithPush(pParse, findRightmost(p)->pWith, 0);
  }

  /* Make sure cursor numbers have been assigned to all entries in
  ** the FROM clause of the SELECT statement.
  */
  sqlite3SrcListAssignCursors(pParse, pTabList);









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    return WRC_Abort;
  }
  if( NEVER(p->pSrc==0) || (selFlags & SF_Expanded)!=0 ){
    return WRC_Prune;
  }
  pTabList = p->pSrc;
  pEList = p->pEList;
  if( p->pWith ){
    sqlite3WithPush(pParse, p->pWith, 0);
  }

  /* Make sure cursor numbers have been assigned to all entries in
  ** the FROM clause of the SELECT statement.
  */
  sqlite3SrcListAssignCursors(pParse, pTabList);
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  w.xExprCallback = sqlite3ExprWalkNoop;
  w.pParse = pParse;
  if( pParse->hasCompound ){
    w.xSelectCallback = convertCompoundSelectToSubquery;
    sqlite3WalkSelect(&w, pSelect);
  }
  w.xSelectCallback = selectExpander;
  if( (pSelect->selFlags & SF_MultiValue)==0 ){
    w.xSelectCallback2 = selectPopWith;
  }
  sqlite3WalkSelect(&w, pSelect);
}


#ifndef SQLITE_OMIT_SUBQUERY
/*
** This is a Walker.xSelectCallback callback for the sqlite3SelectTypeInfo()








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  w.xExprCallback = sqlite3ExprWalkNoop;
  w.pParse = pParse;
  if( pParse->hasCompound ){
    w.xSelectCallback = convertCompoundSelectToSubquery;
    sqlite3WalkSelect(&w, pSelect);
  }
  w.xSelectCallback = selectExpander;

  w.xSelectCallback2 = selectPopWith;

  sqlite3WalkSelect(&w, pSelect);
}


#ifndef SQLITE_OMIT_SUBQUERY
/*
** This is a Walker.xSelectCallback callback for the sqlite3SelectTypeInfo()
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