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Add logic to the query planner to only use partial indices if the WHERE clause

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constrains the search to rows covered by the partial index.  This is just
infrastructure.  The key routine, sqlite3ExprImpliesExpr(), is currently a
no-op so that partial indices will never be used.

FossilOrigin-Name: 8ca3eac111e06a1854f878a74bffe8f20eb47f1b
This commit is contained in:
drh
2013-07-31 23:22:39 +00:00
parent 3780be115a
commit 4bd5f73fa0
5 changed files with 47 additions and 10 deletions
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18
src/where.c
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@@ -4503,6 +4503,17 @@ static Bitmask columnsInIndex(Index *pIdx){
return m;
}
/* Check to see if a partial index with pPartIndexWhere can be used
** in the current query. Return true if it can be and false if not.
*/
static int whereUsablePartialIndex(int iTab, WhereClause *pWC, Expr *pWhere){
int i;
WhereTerm *pTerm;
for(i=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
if( sqlite3ExprImpliesExpr(pTerm->pExpr, pWhere, iTab) ) return 1;
}
return 0;
}
/*
** Add all WhereLoop objects for a single table of the join where the table
@@ -4526,11 +4537,13 @@ static int whereLoopAddBtree(
int b; /* A boolean value */
WhereCost rSize; /* number of rows in the table */
WhereCost rLogSize; /* Logarithm of the number of rows in the table */
WhereClause *pWC; /* The parsed WHERE clause */
pNew = pBuilder->pNew;
pWInfo = pBuilder->pWInfo;
pTabList = pWInfo->pTabList;
pSrc = pTabList->a + pNew->iTab;
pWC = pBuilder->pWC;
assert( !IsVirtual(pSrc->pTab) );
if( pSrc->pIndex ){
@@ -4570,7 +4583,6 @@ static int whereLoopAddBtree(
&& !pSrc->isCorrelated
){
/* Generate auto-index WhereLoops */
WhereClause *pWC = pBuilder->pWC;
WhereTerm *pTerm;
WhereTerm *pWCEnd = pWC->a + pWC->nTerm;
for(pTerm=pWC->a; rc==SQLITE_OK && pTerm<pWCEnd; pTerm++){
@@ -4600,6 +4612,10 @@ static int whereLoopAddBtree(
/* Loop over all indices
*/
for(; rc==SQLITE_OK && pProbe; pProbe=pProbe->pNext, iSortIdx++){
if( pProbe->pPartIdxWhere!=0
&& !whereUsablePartialIndex(pNew->iTab, pWC, pProbe->pPartIdxWhere) ){
continue; /* Partial index inappropriate for this query */
}
pNew->u.btree.nEq = 0;
pNew->nLTerm = 0;
pNew->iSortIdx = 0;