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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Improvements to the HAVING-to-WHERE optimization. The code uses less space and less CPU, and there is now ".selecttrace" output.
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SHA3-256: 5ad668d4339397fe66fe085e0527e37a1930917da88d462a8d89a465faa15e28
User & Date: drh 2018-03-20 18:08:33
Context
2018-03-20
19:02
Fix incorrect testcase labels on two cases in join5.test. No changes to code. check-in: 4661ac81 user: drh tags: trunk
18:08
Improvements to the HAVING-to-WHERE optimization. The code uses less space and less CPU, and there is now ".selecttrace" output. check-in: 5ad668d4 user: drh tags: trunk
16:56
For 'zipfile', detect attempts to cause a duplicate entry via UPDATE. Also, fix handling of 'UPDATE OR REPLACE' statements run on zipfile virtual tables. Win32 portability fixes to the 'fileio' extension. Miscellaneous test fixes. check-in: b36caeca user: mistachkin tags: trunk
Changes
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Changes to src/select.c.

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    );
  }
}
#else
# define explainSimpleCount(a,b,c)
#endif

/*
** Context object for havingToWhereExprCb().
*/
struct HavingToWhereCtx {
  Expr **ppWhere;
  ExprList *pGroupBy;
};

/*
** sqlite3WalkExpr() callback used by havingToWhere().
**
** If the node passed to the callback is a TK_AND node, return 
** WRC_Continue to tell sqlite3WalkExpr() to iterate through child nodes.
**
** Otherwise, return WRC_Prune. In this case, also check if the 
** sub-expression matches the criteria for being moved to the WHERE
** clause. If so, add it to the WHERE clause and replace the sub-expression
** within the HAVING expression with a constant "1".
*/
static int havingToWhereExprCb(Walker *pWalker, Expr *pExpr){
  if( pExpr->op!=TK_AND ){
    struct HavingToWhereCtx *p = pWalker->u.pHavingCtx;
    if( sqlite3ExprIsConstantOrGroupBy(pWalker->pParse, pExpr, p->pGroupBy) ){
      sqlite3 *db = pWalker->pParse->db;
      Expr *pNew = sqlite3ExprAlloc(db, TK_INTEGER, &sqlite3IntTokens[1], 0);
      if( pNew ){
        Expr *pWhere = *(p->ppWhere);
        SWAP(Expr, *pNew, *pExpr);
        pNew = sqlite3ExprAnd(db, pWhere, pNew);
        *(p->ppWhere) = pNew;

      }
    }
    return WRC_Prune;
  }
  return WRC_Continue;
}

................................................................................
**
**   SELECT * FROM <tables> WHERE a=? AND b=? GROUP BY b HAVING c=?
**
** A term of the HAVING expression is eligible for transfer if it consists
** entirely of constants and expressions that are also GROUP BY terms that
** use the "BINARY" collation sequence.
*/
static void havingToWhere(
  Parse *pParse,
  ExprList *pGroupBy,
  Expr *pHaving, 
  Expr **ppWhere
){
  struct HavingToWhereCtx sCtx;
  Walker sWalker;

  sCtx.ppWhere = ppWhere;
  sCtx.pGroupBy = pGroupBy;

  memset(&sWalker, 0, sizeof(sWalker));
  sWalker.pParse = pParse;
  sWalker.xExprCallback = havingToWhereExprCb;
  sWalker.u.pHavingCtx = &sCtx;
  sqlite3WalkExpr(&sWalker, pHaving);






}

/*
** Check to see if the pThis entry of pTabList is a self-join of a prior view.
** If it is, then return the SrcList_item for the prior view.  If it is not,
** then return 0.
*/
................................................................................
    sAggInfo.nSortingColumn = pGroupBy ? pGroupBy->nExpr : 0;
    sAggInfo.pGroupBy = pGroupBy;
    sqlite3ExprAnalyzeAggList(&sNC, pEList);
    sqlite3ExprAnalyzeAggList(&sNC, sSort.pOrderBy);
    if( pHaving ){
      if( pGroupBy ){
        assert( pWhere==p->pWhere );


        havingToWhere(pParse, pGroupBy, pHaving, &p->pWhere);
        pWhere = p->pWhere;
      }
      sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
    }
    sAggInfo.nAccumulator = sAggInfo.nColumn;
    if( p->pGroupBy==0 && p->pHaving==0 && sAggInfo.nFunc==1 ){
      minMaxFlag = minMaxQuery(db, sAggInfo.aFunc[0].pExpr, &pMinMaxOrderBy);







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  }
}
#else
# define explainSimpleCount(a,b,c)
#endif









/*
** sqlite3WalkExpr() callback used by havingToWhere().
**
** If the node passed to the callback is a TK_AND node, return 
** WRC_Continue to tell sqlite3WalkExpr() to iterate through child nodes.
**
** Otherwise, return WRC_Prune. In this case, also check if the 
** sub-expression matches the criteria for being moved to the WHERE
** clause. If so, add it to the WHERE clause and replace the sub-expression
** within the HAVING expression with a constant "1".
*/
static int havingToWhereExprCb(Walker *pWalker, Expr *pExpr){
  if( pExpr->op!=TK_AND ){
    Select *pS = pWalker->u.pSelect;
    if( sqlite3ExprIsConstantOrGroupBy(pWalker->pParse, pExpr, pS->pGroupBy) ){
      sqlite3 *db = pWalker->pParse->db;
      Expr *pNew = sqlite3ExprAlloc(db, TK_INTEGER, &sqlite3IntTokens[1], 0);
      if( pNew ){
        Expr *pWhere = pS->pWhere;
        SWAP(Expr, *pNew, *pExpr);
        pNew = sqlite3ExprAnd(db, pWhere, pNew);
        pS->pWhere = pNew;
        pWalker->eCode = 1;
      }
    }
    return WRC_Prune;
  }
  return WRC_Continue;
}

................................................................................
**
**   SELECT * FROM <tables> WHERE a=? AND b=? GROUP BY b HAVING c=?
**
** A term of the HAVING expression is eligible for transfer if it consists
** entirely of constants and expressions that are also GROUP BY terms that
** use the "BINARY" collation sequence.
*/
static void havingToWhere(Parse *pParse, Select *p){






  Walker sWalker;




  memset(&sWalker, 0, sizeof(sWalker));
  sWalker.pParse = pParse;
  sWalker.xExprCallback = havingToWhereExprCb;
  sWalker.u.pSelect = p;
  sqlite3WalkExpr(&sWalker, p->pHaving);
#if SELECTTRACE_ENABLED
  if( sWalker.eCode && (sqlite3SelectTrace & 0x100)!=0 ){
    SELECTTRACE(0x100,pParse,p,("Move HAVING terms into WHERE:\n"));
    sqlite3TreeViewSelect(0, p, 0);
  }
#endif
}

/*
** Check to see if the pThis entry of pTabList is a self-join of a prior view.
** If it is, then return the SrcList_item for the prior view.  If it is not,
** then return 0.
*/
................................................................................
    sAggInfo.nSortingColumn = pGroupBy ? pGroupBy->nExpr : 0;
    sAggInfo.pGroupBy = pGroupBy;
    sqlite3ExprAnalyzeAggList(&sNC, pEList);
    sqlite3ExprAnalyzeAggList(&sNC, sSort.pOrderBy);
    if( pHaving ){
      if( pGroupBy ){
        assert( pWhere==p->pWhere );
        assert( pHaving==p->pHaving );
        assert( pGroupBy==p->pGroupBy );
        havingToWhere(pParse, p);
        pWhere = p->pWhere;
      }
      sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
    }
    sAggInfo.nAccumulator = sAggInfo.nColumn;
    if( p->pGroupBy==0 && p->pHaving==0 && sAggInfo.nFunc==1 ){
      minMaxFlag = minMaxQuery(db, sAggInfo.aFunc[0].pExpr, &pMinMaxOrderBy);

Changes to src/sqliteInt.h.

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    int n;                                    /* A counter */
    int iCur;                                 /* A cursor number */
    SrcList *pSrcList;                        /* FROM clause */
    struct SrcCount *pSrcCount;               /* Counting column references */
    struct CCurHint *pCCurHint;               /* Used by codeCursorHint() */
    int *aiCol;                               /* array of column indexes */
    struct IdxCover *pIdxCover;               /* Check for index coverage */
    struct IdxExprTrans *pIdxTrans;           /* Convert indexed expr to column */
    ExprList *pGroupBy;                       /* GROUP BY clause */
    struct HavingToWhereCtx *pHavingCtx;      /* HAVING to WHERE clause ctx */
  } u;
};

/* Forward declarations */
int sqlite3WalkExpr(Walker*, Expr*);
int sqlite3WalkExprList(Walker*, ExprList*);
int sqlite3WalkSelect(Walker*, Select*);







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    int n;                                    /* A counter */
    int iCur;                                 /* A cursor number */
    SrcList *pSrcList;                        /* FROM clause */
    struct SrcCount *pSrcCount;               /* Counting column references */
    struct CCurHint *pCCurHint;               /* Used by codeCursorHint() */
    int *aiCol;                               /* array of column indexes */
    struct IdxCover *pIdxCover;               /* Check for index coverage */
    struct IdxExprTrans *pIdxTrans;           /* Convert idxed expr to column */
    ExprList *pGroupBy;                       /* GROUP BY clause */
    Select *pSelect;                          /* HAVING to WHERE clause ctx */
  } u;
};

/* Forward declarations */
int sqlite3WalkExpr(Walker*, Expr*);
int sqlite3WalkExprList(Walker*, ExprList*);
int sqlite3WalkSelect(Walker*, Select*);