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Improvements to the HAVING-to-WHERE optimization. The code uses less space

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and less CPU, and there is now ".selecttrace" output.

FossilOrigin-Name: 5ad668d4339397fe66fe085e0527e37a1930917da88d462a8d89a465faa15e28
This commit is contained in:
drh
2018-03-20 18:08:33 +00:00
parent de8113c31e
commit cd0abc24d1
4 changed files with 28 additions and 38 deletions
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43
src/select.c
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@@ -4912,14 +4912,6 @@ static void explainSimpleCount(
# define explainSimpleCount(a,b,c)
#endif
/*
** Context object for havingToWhereExprCb().
*/
struct HavingToWhereCtx {
Expr **ppWhere;
ExprList *pGroupBy;
};
/*
** sqlite3WalkExpr() callback used by havingToWhere().
**
@@ -4933,15 +4925,16 @@ struct HavingToWhereCtx {
*/
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) ){
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 = *(p->ppWhere);
Expr *pWhere = pS->pWhere;
SWAP(Expr, *pNew, *pExpr);
pNew = sqlite3ExprAnd(db, pWhere, pNew);
*(p->ppWhere) = pNew;
pS->pWhere = pNew;
pWalker->eCode = 1;
}
}
return WRC_Prune;
@@ -4964,23 +4957,19 @@ static int havingToWhereExprCb(Walker *pWalker, Expr *pExpr){
** 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;
static void havingToWhere(Parse *pParse, Select *p){
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);
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
}
/*
@@ -5649,7 +5638,9 @@ int sqlite3Select(
if( pHaving ){
if( pGroupBy ){
assert( pWhere==p->pWhere );
havingToWhere(pParse, pGroupBy, pHaving, &p->pWhere);
assert( pHaving==p->pHaving );
assert( pGroupBy==p->pGroupBy );
havingToWhere(pParse, p);
pWhere = p->pWhere;
}
sqlite3ExprAnalyzeAggregates(&sNC, pHaving);