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Experimental change to support the covering index optimization for queries with OR terms in the WHERE clause that search a single index more than once.

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FossilOrigin-Name: 1dc8c7c741a82bb98a07f3fdb8142d8bc8d8a98b
This commit is contained in:
dan
2012-08-24 10:52:35 +00:00
parent fb0a60819b
commit bfca6a4066
5 changed files with 96 additions and 13 deletions
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50
src/where.c
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@@ -4297,6 +4297,8 @@ static Bitmask codeOneLoopStart(
*/
WhereClause *pOrWc; /* The OR-clause broken out into subterms */
SrcList *pOrTab; /* Shortened table list or OR-clause generation */
Index *pCov = 0; /* Potential covering index (or NULL) */
int iCovCur = 0; /* Cursor used to open pCov */
int regReturn = ++pParse->nMem; /* Register used with OP_Gosub */
int regRowset = 0; /* Register for RowSet object */
@@ -4315,7 +4317,7 @@ static Bitmask codeOneLoopStart(
pLevel->op = OP_Return;
pLevel->p1 = regReturn;
/* Set up a new SrcList ni pOrTab containing the table being scanned
/* Set up a new SrcList in pOrTab containing the table being scanned
** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
*/
@@ -4393,7 +4395,9 @@ static Bitmask codeOneLoopStart(
pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
WHERE_OMIT_OPEN_CLOSE | WHERE_AND_ONLY |
WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY);
assert( pSubWInfo || pParse->nErr || pParse->db->mallocFailed );
if( pSubWInfo ){
WhereLevel *pLvl;
explainOneScan(
pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
);
@@ -4414,11 +4418,45 @@ static Bitmask codeOneLoopStart(
*/
if( pSubWInfo->untestedTerms ) untestedTerms = 1;
/* If all of the OR-connected terms are optimized using the same
** index, and the index is opened using the same cursor number
** by each call to sqlite3WhereBegin() made by this loop, it may
** be possible to use that index as a covering index.
**
** If the call to sqlite3WhereBegin() above resulted in a scan that
** uses an index, and this is either the first OR-connected term
** processed or the index is the same as that used by all previous
** terms, set pCov to the candidate covering index and iCovCur to
** the cursor number used to open it. Otherwise, set pCov to NULL
** to indicate that no candidate covering index will be available.
*/
pLvl = &pSubWInfo->a[0];
if( (pLvl->plan.wsFlags & WHERE_INDEXED)!=0
&& (pLvl->plan.wsFlags & WHERE_TEMP_INDEX)==0
&& (pLvl->iIdxCur==pParse->nTab-1)
&& (ii==0 || (pLvl->plan.u.pIdx==pCov && pLvl->iIdxCur==iCovCur))
){
pCov = pLvl->plan.u.pIdx;
iCovCur = pLvl->iIdxCur;
/* Decrement pParse->nTab in order to make cursor number iCovCur
** available to the next OR-connected term. */
pParse->nTab--;
}else{
pCov = 0;
}
/* Finish the loop through table entries that match term pOrTerm. */
sqlite3WhereEnd(pSubWInfo);
}
}
}
/* Increment pParse->nTab here to ensure that it really is larger than
** the largest cursor number used by the VM (this may not be the case
** if pParse->nTab was decremented by the final iteration of the loop
** above). */
pParse->nTab++;
pLevel->pCovidx = pCov;
pLevel->iIdxCur = iCovCur;
if( pAndExpr ){
pAndExpr->pLeft = 0;
sqlite3ExprDelete(pParse->db, pAndExpr);
@@ -5208,6 +5246,7 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
*/
assert( pWInfo->nLevel==1 || pWInfo->nLevel==pTabList->nSrc );
for(i=0, pLevel=pWInfo->a; i<pWInfo->nLevel; i++, pLevel++){
Index *pIdx = 0;
struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
Table *pTab = pTabItem->pTab;
assert( pTab!=0 );
@@ -5237,12 +5276,15 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
** that reference the table and converts them into opcodes that
** reference the index.
*/
if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 && !db->mallocFailed){
if( pLevel->plan.wsFlags & WHERE_INDEXED ){
pIdx = pLevel->plan.u.pIdx;
}else if( pLevel->plan.wsFlags & WHERE_MULTI_OR ){
pIdx = pLevel->pCovidx;
}
if( pIdx && !db->mallocFailed){
int k, j, last;
VdbeOp *pOp;
Index *pIdx = pLevel->plan.u.pIdx;
assert( pIdx!=0 );
pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
last = sqlite3VdbeCurrentAddr(v);
for(k=pWInfo->iTop; k<last; k++, pOp++){