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Reuse the same materialization of a view when that view appears in a query

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more than once, such as in a self-join.

FossilOrigin-Name: 9e35c89dbe744312f612e507b51ff9a5bb656def75392d25bc19fc638548cd1e
This commit is contained in:
drh
2017-05-02 17:54:19 +00:00
parent a1f5c0c90b ed71298085
commit 3f4df4c6f3
5 changed files with 79 additions and 15 deletions
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39
src/select.c
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@@ -4950,6 +4950,32 @@ static void havingToWhere(
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.
*/
static struct SrcList_item *isSelfJoinView(
SrcList *pTabList, /* Search for self-joins in this FROM clause */
struct SrcList_item *pThis /* Search for prior reference to this subquery */
){
struct SrcList_item *pItem;
for(pItem = pTabList->a; pItem<pThis; pItem++){
if( pItem->pSelect==0 ) continue;
if( pItem->fg.viaCoroutine ) continue;
if( pItem->zName==0 ) continue;
if( sqlite3_stricmp(pItem->zDatabase, pThis->zDatabase)!=0 ) continue;
if( sqlite3_stricmp(pItem->zName, pThis->zName)!=0 ) continue;
if( sqlite3ExprCompare(pThis->pSelect->pWhere, pItem->pSelect->pWhere, -1) ){
/* The view was modified by some other optimization such as
** pushDownWhereTerms() */
continue;
}
return pItem;
}
return 0;
}
/*
** Generate code for the SELECT statement given in the p argument.
**
@@ -5184,6 +5210,8 @@ int sqlite3Select(
int topAddr;
int onceAddr = 0;
int retAddr;
struct SrcList_item *pPrior;
assert( pItem->addrFillSub==0 );
pItem->regReturn = ++pParse->nMem;
topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn);
@@ -5197,9 +5225,14 @@ int sqlite3Select(
}else{
VdbeNoopComment((v, "materialize \"%s\"", pItem->pTab->zName));
}
sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
sqlite3Select(pParse, pSub, &dest);
pPrior = isSelfJoinView(pTabList, pItem);
if( pPrior ){
sqlite3VdbeAddOp2(v, OP_OpenDup, pItem->iCursor, pPrior->iCursor);
}else{
sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
sqlite3Select(pParse, pSub, &dest);
}
pItem->pTab->nRowLogEst = pSub->nSelectRow;
if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
retAddr = sqlite3VdbeAddOp1(v, OP_Return, pItem->regReturn);