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Avoid passing constraints that are unusable due to LEFT or CROSS joins to virtual table xBestIndex() methods.

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FossilOrigin-Name: 80ee56dda7db3860f8be5f6968c8745138f8453f
This commit is contained in:
dan
2015-06-08 18:05:54 +00:00
parent f5b5f9b972
commit 4f20cd402b
4 changed files with 150 additions and 23 deletions
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69
src/where.c
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@@ -757,6 +757,7 @@ end_auto_index_create:
static sqlite3_index_info *allocateIndexInfo(
Parse *pParse,
WhereClause *pWC,
Bitmask mUnusable, /* Ignore terms with these prereqs */
struct SrcList_item *pSrc,
ExprList *pOrderBy
){
@@ -773,6 +774,7 @@ static sqlite3_index_info *allocateIndexInfo(
** to this virtual table */
for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
if( pTerm->leftCursor != pSrc->iCursor ) continue;
if( pTerm->prereqRight & mUnusable ) continue;
assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
testcase( pTerm->eOperator & WO_IN );
testcase( pTerm->eOperator & WO_ISNULL );
@@ -827,6 +829,7 @@ static sqlite3_index_info *allocateIndexInfo(
for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
u8 op;
if( pTerm->leftCursor != pSrc->iCursor ) continue;
if( pTerm->prereqRight & mUnusable ) continue;
assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
testcase( pTerm->eOperator & WO_IN );
testcase( pTerm->eOperator & WO_IS );
@@ -2666,10 +2669,32 @@ static int whereLoopAddBtree(
/*
** Add all WhereLoop objects for a table of the join identified by
** pBuilder->pNew->iTab. That table is guaranteed to be a virtual table.
**
** If there are no LEFT or CROSS JOIN joins in the query, both mExtra and
** mUnusable are set to 0. Otherwise, mExtra is a mask of all FROM clause
** entries that occur before the virtual table in the FROM clause and are
** separated from it by at least one LEFT or CROSS JOIN. Similarly, the
** mUnusable mask contains all FROM clause entries that occur after the
** virtual table and are separated from it by at least one LEFT or
** CROSS JOIN.
**
** For example, if the query were:
**
** ... FROM t1, t2 LEFT JOIN t3, t4, vt CROSS JOIN t5, t6;
**
** then mExtra corresponds to (t1, t2) and mUnusable to (t5, t6).
**
** All the tables in mExtra must be scanned before the current virtual
** table. So any terms for which all prerequisites are satisfied by
** mExtra may be specified as "usable" in all calls to xBestIndex.
** Conversely, all tables in mUnusable must be scanned after the current
** virtual table, so any terms for which the prerequisites overlap with
** mUnusable should always be configured as "not-usable" for xBestIndex.
*/
static int whereLoopAddVirtual(
WhereLoopBuilder *pBuilder, /* WHERE clause information */
Bitmask mExtra
Bitmask mExtra, /* Tables that must be scanned before this one */
Bitmask mUnusable /* Tables that must be scanned after this one */
){
WhereInfo *pWInfo; /* WHERE analysis context */
Parse *pParse; /* The parsing context */
@@ -2690,6 +2715,7 @@ static int whereLoopAddVirtual(
WhereLoop *pNew;
int rc = SQLITE_OK;
assert( (mExtra & mUnusable)==0 );
pWInfo = pBuilder->pWInfo;
pParse = pWInfo->pParse;
db = pParse->db;
@@ -2698,7 +2724,7 @@ static int whereLoopAddVirtual(
pSrc = &pWInfo->pTabList->a[pNew->iTab];
pTab = pSrc->pTab;
assert( IsVirtual(pTab) );
pIdxInfo = allocateIndexInfo(pParse, pWC, pSrc, pBuilder->pOrderBy);
pIdxInfo = allocateIndexInfo(pParse, pWC, mUnusable, pSrc,pBuilder->pOrderBy);
if( pIdxInfo==0 ) return SQLITE_NOMEM;
pNew->prereq = 0;
pNew->rSetup = 0;
@@ -2728,7 +2754,7 @@ static int whereLoopAddVirtual(
if( (pTerm->eOperator & WO_IN)!=0 ){
seenIn = 1;
}
if( pTerm->prereqRight!=0 ){
if( (pTerm->prereqRight & ~mExtra)!=0 ){
seenVar = 1;
}else if( (pTerm->eOperator & WO_IN)==0 ){
pIdxCons->usable = 1;
@@ -2736,7 +2762,7 @@ static int whereLoopAddVirtual(
break;
case 1: /* Constants with IN operators */
assert( seenIn );
pIdxCons->usable = (pTerm->prereqRight==0);
pIdxCons->usable = (pTerm->prereqRight & ~mExtra)==0;
break;
case 2: /* Variables without IN */
assert( seenVar );
@@ -2835,7 +2861,11 @@ whereLoopAddVtab_exit:
** Add WhereLoop entries to handle OR terms. This works for either
** btrees or virtual tables.
*/
static int whereLoopAddOr(WhereLoopBuilder *pBuilder, Bitmask mExtra){
static int whereLoopAddOr(
WhereLoopBuilder *pBuilder,
Bitmask mExtra,
Bitmask mUnusable
){
WhereInfo *pWInfo = pBuilder->pWInfo;
WhereClause *pWC;
WhereLoop *pNew;
@@ -2894,14 +2924,14 @@ static int whereLoopAddOr(WhereLoopBuilder *pBuilder, Bitmask mExtra){
#endif
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( IsVirtual(pItem->pTab) ){
rc = whereLoopAddVirtual(&sSubBuild, mExtra);
rc = whereLoopAddVirtual(&sSubBuild, mExtra, mUnusable);
}else
#endif
{
rc = whereLoopAddBtree(&sSubBuild, mExtra);
}
if( rc==SQLITE_OK ){
rc = whereLoopAddOr(&sSubBuild, mExtra);
rc = whereLoopAddOr(&sSubBuild, mExtra, mUnusable);
}
assert( rc==SQLITE_OK || sCur.n==0 );
if( sCur.n==0 ){
@@ -2963,33 +2993,44 @@ static int whereLoopAddAll(WhereLoopBuilder *pBuilder){
int iTab;
SrcList *pTabList = pWInfo->pTabList;
struct SrcList_item *pItem;
struct SrcList_item *pEnd = &pTabList->a[pWInfo->nLevel];
sqlite3 *db = pWInfo->pParse->db;
int nTabList = pWInfo->nLevel;
int rc = SQLITE_OK;
u8 priorJoinType = 0;
WhereLoop *pNew;
pNew = pBuilder->pNew;
whereLoopInit(pNew);
/* Loop over the tables in the join, from left to right */
pNew = pBuilder->pNew;
whereLoopInit(pNew);
for(iTab=0, pItem=pTabList->a; iTab<nTabList; iTab++, pItem++){
for(iTab=0, pItem=pTabList->a; pItem<pEnd; iTab++, pItem++){
Bitmask mUnusable = 0;
pNew->iTab = iTab;
pNew->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, pItem->iCursor);
if( ((pItem->jointype|priorJoinType) & (JT_LEFT|JT_CROSS))!=0 ){
if( (pItem->jointype & (JT_LEFT|JT_CROSS))!=0 ){
/* This condition is true when pItem is the FROM clause term on the
** right-hand-side of a LEFT or CROSS JOIN. */
mExtra = mPrior;
}
priorJoinType = pItem->jointype;
if( IsVirtual(pItem->pTab) ){
rc = whereLoopAddVirtual(pBuilder, mExtra);
struct SrcList_item *p;
for(p=&pItem[1]; p<pEnd; p++){
if( mUnusable || (p->jointype & (JT_LEFT|JT_CROSS)) ){
mUnusable |= sqlite3WhereGetMask(&pWInfo->sMaskSet, p->iCursor);
}
}
rc = whereLoopAddVirtual(pBuilder, mExtra, mUnusable);
}else{
rc = whereLoopAddBtree(pBuilder, mExtra);
}
if( rc==SQLITE_OK ){
rc = whereLoopAddOr(pBuilder, mExtra);
rc = whereLoopAddOr(pBuilder, mExtra, mUnusable);
}
mPrior |= pNew->maskSelf;
if( rc || db->mallocFailed ) break;
}
whereLoopClear(db, pNew);
return rc;
}