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Materialize any CTE that is used more than once.

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FossilOrigin-Name: ba59159fbe6b83fb6d79fbfee22d983768b0ebbaac7e99d2ac66c810e5e04100
This commit is contained in:
drh
2021-02-21 23:44:14 +00:00
parent 7601294ad3
commit a79e2a2d28
9 changed files with 117 additions and 42 deletions
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75
src/select.c
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@@ -4726,7 +4726,7 @@ int sqlite3IndexedByLookup(Parse *pParse, SrcItem *pFrom){
pParse->checkSchema = 1;
return SQLITE_ERROR;
}
pFrom->pIBIndex = pIdx;
pFrom->u2.pIBIndex = pIdx;
return SQLITE_OK;
}
@@ -4935,8 +4935,18 @@ static int resolveFromTermToCte(
if( cannotBeFunction(pParse, pFrom) ) return 2;
assert( pFrom->pTab==0 );
pFrom->pTab = pTab = sqlite3DbMallocZero(db, sizeof(Table));
pTab = sqlite3DbMallocZero(db, sizeof(Table));
if( pTab==0 ) return 2;
if( pCte->pUse==0 ){
pCte->pUse = sqlite3DbMallocZero(db, sizeof(pCte->pUse[0]));
if( pCte->pUse==0
|| sqlite3ParserAddCleanup(pParse,sqlite3DbFree,pCte->pUse)==0
){
sqlite3DbFree(db, pTab);
return 2;
}
}
pFrom->pTab = pTab;
pTab->nTabRef = 1;
pTab->zName = sqlite3DbStrDup(db, pCte->zName);
pTab->iPKey = -1;
@@ -4945,6 +4955,9 @@ static int resolveFromTermToCte(
pFrom->pSelect = sqlite3SelectDup(db, pCte->pSelect, 0);
if( db->mallocFailed ) return 2;
assert( pFrom->pSelect );
pFrom->fg.isCte = 1;
pFrom->u2.pCteUse = pCte->pUse;
pCte->pUse->nUse++;
/* Check if this is a recursive CTE. */
pRecTerm = pSel = pFrom->pSelect;
@@ -6153,6 +6166,7 @@ int sqlite3Select(
*/
for(i=0; i<pTabList->nSrc; i++){
SrcItem *pItem = &pTabList->a[i];
SrcItem *pPrior;
SelectDest dest;
Select *pSub;
#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
@@ -6212,6 +6226,7 @@ int sqlite3Select(
** inside the subquery. This can help the subquery to run more efficiently.
*/
if( OptimizationEnabled(db, SQLITE_PushDown)
&& (pItem->fg.isCte==0 || pItem->u2.pCteUse->nUse<=1)
&& pushDownWhereTerms(pParse, pSub, p->pWhere, pItem->iCursor,
(pItem->fg.jointype & JT_OUTER)!=0)
){
@@ -6232,16 +6247,18 @@ int sqlite3Select(
/* Generate code to implement the subquery
**
** The subquery is implemented as a co-routine if the subquery is
** guaranteed to be the outer loop (so that it does not need to be
** computed more than once)
** The subquery is implemented as a co-routine if:
** (1) the subquery is guaranteed to be the outer loop (so that
** it does not need to be computed more than once), and
** (2) the subquery is not a CTE that is used more then once.
**
** TODO: Are there other reasons beside (1) to use a co-routine
** TODO: Are there other reasons beside (1) and (2) to use a co-routine
** implementation?
*/
if( i==0
&& (pTabList->nSrc==1
|| (pTabList->a[1].fg.jointype&(JT_LEFT|JT_CROSS))!=0) /* (1) */
&& (pItem->fg.isCte==0 || pItem->u2.pCteUse->nUse<2) /* (2) */
){
/* Implement a co-routine that will return a single row of the result
** set on each invocation.
@@ -6261,16 +6278,30 @@ int sqlite3Select(
sqlite3VdbeEndCoroutine(v, pItem->regReturn);
sqlite3VdbeJumpHere(v, addrTop-1);
sqlite3ClearTempRegCache(pParse);
}else if( pItem->fg.isCte && pItem->u2.pCteUse->addrM9e>0 ){
/* This is a CTE for which materialization code has already been
** generated. Invoke the subroutine to compute the materialization,
** the make the pItem->iCursor be a copy of the ephemerial table that
** holds the result of the materialization. */
CteUse *pCteUse = pItem->u2.pCteUse;
sqlite3VdbeAddOp2(v, OP_Gosub, pCteUse->regRtn, pCteUse->addrM9e);
if( pItem->iCursor!=pCteUse->iCur ){
sqlite3VdbeAddOp2(v, OP_OpenDup, pItem->iCursor, pCteUse->iCur);
}
pSub->nSelectRow = pCteUse->nRowEst;
}else if( (pPrior = isSelfJoinView(pTabList, pItem))!=0 ){
/* This view has already been materialized by a prior entry in
** this same FROM clause. Reuse it. */
if( pPrior->addrFillSub ){
sqlite3VdbeAddOp2(v, OP_Gosub, pPrior->regReturn, pPrior->addrFillSub);
}
sqlite3VdbeAddOp2(v, OP_OpenDup, pItem->iCursor, pPrior->iCursor);
pSub->nSelectRow = pPrior->pSelect->nSelectRow;
}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
*/
/* Generate a subroutine that will materialize the view. */
int topAddr;
int onceAddr = 0;
int retAddr;
SrcItem *pPrior;
testcase( pItem->addrFillSub==0 ); /* Ticket c52b09c7f38903b1311 */
pItem->regReturn = ++pParse->nMem;
@@ -6285,22 +6316,22 @@ int sqlite3Select(
}else{
VdbeNoopComment((v, "materialize \"%s\"", pItem->pTab->zName));
}
pPrior = isSelfJoinView(pTabList, pItem);
if( pPrior ){
sqlite3VdbeAddOp2(v, OP_OpenDup, pItem->iCursor, pPrior->iCursor);
assert( pPrior->pSelect!=0 );
pSub->nSelectRow = pPrior->pSelect->nSelectRow;
}else{
sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
ExplainQueryPlan((pParse, 1, "MATERIALIZE %u", pSub->selId));
sqlite3Select(pParse, pSub, &dest);
}
sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
ExplainQueryPlan((pParse, 1, "MATERIALIZE %u", pSub->selId));
sqlite3Select(pParse, pSub, &dest);
pItem->pTab->nRowLogEst = 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( pItem->fg.isCte ){
CteUse *pCteUse = pItem->u2.pCteUse;
pCteUse->addrM9e = pItem->addrFillSub;
pCteUse->regRtn = pItem->regReturn;
pCteUse->iCur = pItem->iCursor;
pCteUse->nRowEst = pSub->nSelectRow;
}
}
if( db->mallocFailed ) goto select_end;
pParse->nHeight -= sqlite3SelectExprHeight(p);