}
#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/*
+** Make copies of relevant WHERE clause terms of the outer query into
+** the WHERE clause of subquery. Example:
+**
+** SELECT * FROM (SELECT a AS x, c-d AS y FROM t1) WHERE x=5 AND y=10;
+**
+** Transformed into:
+**
+** SELECT * FROM (SELECT a AS x, c-d AS y FROM t1 WHERE a=5 AND c-d=10)
+** WHERE x=5 AND y=10;
+**
+** The hope is that the terms added to the inner query will make it more
+** efficient.
+**
+** Do not attempt this optimization if:
+**
+** (1) The inner query is an aggregate. (In that case, we'd really want
+** to copy the outer WHERE-clause terms onto the HAVING clause of the
+** inner query. But they probably won't help there so do not bother.)
+**
+** (2) The inner query is the recursive part of a common table expression.
+**
+** (3) The inner query has a LIMIT clause (since the changes to the WHERE
+** close would change the meaning of the LIMIT).
+**
+** (4) The inner query is the right operand of a LEFT JOIN. (The caller
+** enforces this restriction since this routine does not have enough
+** information to know.)
+**
+** Return 0 if no changes are made and non-zero if one or more WHERE clause
+** terms are duplicated into the subquery.
+*/
+static int pushDownWhereTerms(
+ sqlite3 *db, /* The database connection (for malloc()) */
+ Select *pSubq, /* The subquery whose WHERE clause is to be augmented */
+ Expr *pWhere, /* The WHERE clause of the outer query */
+ int iCursor /* Cursor number of the subquery */
+){
+ Expr *pNew;
+ int nChng = 0;
+ if( pWhere==0 ) return 0;
+ if( (pSubq->selFlags & (SF_Aggregate|SF_Recursive))!=0 ){
+ return 0; /* restrictions (1) and (2) */
+ }
+ if( pSubq->pLimit!=0 ){
+ return 0; /* restriction (3) */
+ }
+ while( pWhere->op==TK_AND ){
+ nChng += pushDownWhereTerms(db, pSubq, pWhere->pRight, iCursor);
+ pWhere = pWhere->pLeft;
+ }
+ if( sqlite3ExprIsTableConstant(pWhere, iCursor) ){
+ nChng++;
+ while( pSubq ){
+ pNew = sqlite3ExprDup(db, pWhere, 0);
+ pNew = substExpr(db, pNew, iCursor, pSubq->pEList);
+ pSubq->pWhere = sqlite3ExprAnd(db, pSubq->pWhere, pNew);
+ pSubq = pSubq->pPrior;
+ }
+ }
+ return nChng;
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
/*
** Based on the contents of the AggInfo structure indicated by the first
** argument, this function checks if the following are true:
p->selFlags |= SF_Aggregate;
}
i = -1;
- }else if( pTabList->nSrc==1
- && (p->selFlags & SF_All)==0
- && OptimizationEnabled(db, SQLITE_SubqCoroutine)
- ){
- /* Implement a co-routine that will return a single row of the result
- ** set on each invocation.
- */
- int addrTop = sqlite3VdbeCurrentAddr(v)+1;
- pItem->regReturn = ++pParse->nMem;
- sqlite3VdbeAddOp3(v, OP_InitCoroutine, pItem->regReturn, 0, addrTop);
- VdbeComment((v, "%s", pItem->pTab->zName));
- pItem->addrFillSub = addrTop;
- sqlite3SelectDestInit(&dest, SRT_Coroutine, pItem->regReturn);
- explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
- sqlite3Select(pParse, pSub, &dest);
- pItem->pTab->nRowLogEst = sqlite3LogEst(pSub->nSelectRow);
- pItem->viaCoroutine = 1;
- pItem->regResult = dest.iSdst;
- sqlite3VdbeAddOp1(v, OP_EndCoroutine, pItem->regReturn);
- sqlite3VdbeJumpHere(v, addrTop-1);
- sqlite3ClearTempRegCache(pParse);
}else{
- /* Generate a subroutine that will fill an ephemeral table with
- ** the content of this subquery. pItem->addrFillSub will point
- ** to the address of the generated subroutine. pItem->regReturn
- ** is a register allocated to hold the subroutine return address
- */
- int topAddr;
- int onceAddr = 0;
- int retAddr;
- assert( pItem->addrFillSub==0 );
- pItem->regReturn = ++pParse->nMem;
- topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn);
- pItem->addrFillSub = topAddr+1;
- if( pItem->isCorrelated==0 ){
- /* If the subquery is not correlated and if we are not inside of
- ** a trigger, then we only need to compute the value of the subquery
- ** once. */
- onceAddr = sqlite3CodeOnce(pParse); VdbeCoverage(v);
- VdbeComment((v, "materialize \"%s\"", pItem->pTab->zName));
+ if( (pItem->jointype & JT_OUTER)==0
+ && pushDownWhereTerms(db, pSub, p->pWhere, pItem->iCursor)
+ ){
+#if SELECTTRACE_ENABLED
+ if( sqlite3SelectTrace & 0x100 ){
+ sqlite3DebugPrintf("After WHERE-clause push-down:\n");
+ sqlite3TreeViewSelect(0, p, 0);
+ }
+#endif
+ }
+ if( pTabList->nSrc==1
+ && (p->selFlags & SF_All)==0
+ && OptimizationEnabled(db, SQLITE_SubqCoroutine)
+ ){
+ /* Implement a co-routine that will return a single row of the result
+ ** set on each invocation.
+ */
+ int addrTop = sqlite3VdbeCurrentAddr(v)+1;
+ pItem->regReturn = ++pParse->nMem;
+ sqlite3VdbeAddOp3(v, OP_InitCoroutine, pItem->regReturn, 0, addrTop);
+ VdbeComment((v, "%s", pItem->pTab->zName));
+ pItem->addrFillSub = addrTop;
+ sqlite3SelectDestInit(&dest, SRT_Coroutine, pItem->regReturn);
+ explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
+ sqlite3Select(pParse, pSub, &dest);
+ pItem->pTab->nRowLogEst = sqlite3LogEst(pSub->nSelectRow);
+ pItem->viaCoroutine = 1;
+ pItem->regResult = dest.iSdst;
+ sqlite3VdbeAddOp1(v, OP_EndCoroutine, pItem->regReturn);
+ sqlite3VdbeJumpHere(v, addrTop-1);
+ sqlite3ClearTempRegCache(pParse);
}else{
- VdbeNoopComment((v, "materialize \"%s\"", pItem->pTab->zName));
+ /* Generate a subroutine that will fill an ephemeral table with
+ ** the content of this subquery. pItem->addrFillSub will point
+ ** to the address of the generated subroutine. pItem->regReturn
+ ** is a register allocated to hold the subroutine return address
+ */
+ int topAddr;
+ int onceAddr = 0;
+ int retAddr;
+ assert( pItem->addrFillSub==0 );
+ pItem->regReturn = ++pParse->nMem;
+ topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn);
+ pItem->addrFillSub = topAddr+1;
+ if( pItem->isCorrelated==0 ){
+ /* If the subquery is not correlated and if we are not inside of
+ ** a trigger, then we only need to compute the value of the subquery
+ ** once. */
+ onceAddr = sqlite3CodeOnce(pParse); VdbeCoverage(v);
+ VdbeComment((v, "materialize \"%s\"", pItem->pTab->zName));
+ }else{
+ VdbeNoopComment((v, "materialize \"%s\"", pItem->pTab->zName));
+ }
+ sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
+ explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
+ sqlite3Select(pParse, pSub, &dest);
+ pItem->pTab->nRowLogEst = sqlite3LogEst(pSub->nSelectRow);
+ if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
+ retAddr = sqlite3VdbeAddOp1(v, OP_Return, pItem->regReturn);
+ VdbeComment((v, "end %s", pItem->pTab->zName));
+ sqlite3VdbeChangeP1(v, topAddr, retAddr);
+ sqlite3ClearTempRegCache(pParse);
}
- sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
- explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
- sqlite3Select(pParse, pSub, &dest);
- pItem->pTab->nRowLogEst = sqlite3LogEst(pSub->nSelectRow);
- if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
- retAddr = sqlite3VdbeAddOp1(v, OP_Return, pItem->regReturn);
- VdbeComment((v, "end %s", pItem->pTab->zName));
- sqlite3VdbeChangeP1(v, topAddr, retAddr);
- sqlite3ClearTempRegCache(pParse);
}
- if( /*pParse->nErr ||*/ db->mallocFailed ){
+ if( db->mallocFailed ){
goto select_end;
}
pParse->nHeight -= sqlite3SelectExprHeight(p);
projects / thirdparty / sqlite.git / commitdiff
