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When generating individual loops for each ORed term of an OR scan, move any

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constant WHERE expressions outside of the loop, as is done for top-level
loops.

FossilOrigin-Name: e4a022be4b069b08cfdfda5295461676b99d28e17bbbedfbcb362dec69de59bd
This commit is contained in:
dan
2017-06-22 16:51:16 +00:00
parent c45fdb2a7f
commit c456a76fb3
7 changed files with 131 additions and 32 deletions
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55
src/where.c
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@@ -4294,6 +4294,31 @@ static int whereShortCut(WhereLoopBuilder *pBuilder){
return 0;
}
/*
** Helper function for exprIsDeterministic().
*/
static int exprNodeIsDeterministic(Walker *pWalker, Expr *pExpr){
if( pExpr->op==TK_FUNCTION && ExprHasProperty(pExpr, EP_ConstFunc)==0 ){
pWalker->eCode = 0;
return WRC_Abort;
}
return WRC_Continue;
}
/*
** Return true if the expression contains no non-deterministic SQL
** functions. Do not consider non-deterministic SQL functions that are
** part of sub-select statements.
*/
static int exprIsDeterministic(Expr *p){
Walker w;
memset(&w, 0, sizeof(w));
w.eCode = 1;
w.xExprCallback = exprNodeIsDeterministic;
sqlite3WalkExpr(&w, p);
return w.eCode;
}
/*
** Generate the beginning of the loop used for WHERE clause processing.
** The return value is a pointer to an opaque structure that contains
@@ -4492,17 +4517,6 @@ WhereInfo *sqlite3WhereBegin(
sqlite3WhereClauseInit(&pWInfo->sWC, pWInfo);
sqlite3WhereSplit(&pWInfo->sWC, pWhere, TK_AND);
/* Special case: a WHERE clause that is constant. Evaluate the
** expression and either jump over all of the code or fall thru.
*/
for(ii=0; ii<sWLB.pWC->nTerm; ii++){
if( nTabList==0 || sqlite3ExprIsConstantNotJoin(sWLB.pWC->a[ii].pExpr) ){
sqlite3ExprIfFalse(pParse, sWLB.pWC->a[ii].pExpr, pWInfo->iBreak,
SQLITE_JUMPIFNULL);
sWLB.pWC->a[ii].wtFlags |= TERM_CODED;
}
}
/* Special case: No FROM clause
*/
if( nTabList==0 ){
@@ -4541,6 +4555,25 @@ WhereInfo *sqlite3WhereBegin(
sqlite3WhereExprAnalyze(pTabList, &pWInfo->sWC);
if( db->mallocFailed ) goto whereBeginError;
/* Special case: WHERE terms that do not refer to any tables in the join
** (constant expressions). Evaluate each such term, and jump over all the
** generated code if the result is not true.
**
** Do not do this if the expression contains non-deterministic functions
** that are not within a sub-select. This is not strictly required, but
** preserves SQLite's legacy behaviour in the following two cases:
**
** FROM ... WHERE random()>0; -- eval random() once per row
** FROM ... WHERE (SELECT random())>0; -- eval random() once overall
*/
for(ii=0; ii<sWLB.pWC->nTerm; ii++){
WhereTerm *pT = &sWLB.pWC->a[ii];
if( pT->prereqAll==0 && (nTabList==0 || exprIsDeterministic(pT->pExpr)) ){
sqlite3ExprIfFalse(pParse, pT->pExpr, pWInfo->iBreak, SQLITE_JUMPIFNULL);
pT->wtFlags |= TERM_CODED;
}
}
if( wctrlFlags & WHERE_WANT_DISTINCT ){
if( isDistinctRedundant(pParse, pTabList, &pWInfo->sWC, pResultSet) ){
/* The DISTINCT marking is pointless. Ignore it. */