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Experimental changes to improve optimization of DISTINCT queries.

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FossilOrigin-Name: f7ba0219ef2f235543c258be736955d91ca5ecce
This commit is contained in:
dan
2011-06-30 20:17:15 +00:00
parent e1b4f0f177
commit 38cc40c216
14 changed files with 219 additions and 66 deletions
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65
src/select.c
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@@ -3721,6 +3721,7 @@ int sqlite3Select(
int distinct; /* Table to use for the distinct set */
int rc = 1; /* Value to return from this function */
int addrSortIndex; /* Address of an OP_OpenEphemeral instruction */
int addrDistinctIndex; /* Address of an OP_OpenEphemeral instruction */
AggInfo sAggInfo; /* Information used by aggregate queries */
int iEnd; /* Address of the end of the query */
sqlite3 *db; /* The database connection */
@@ -3850,12 +3851,14 @@ int sqlite3Select(
/* If possible, rewrite the query to use GROUP BY instead of DISTINCT.
** GROUP BY might use an index, DISTINCT never does.
*/
#if 0
assert( p->pGroupBy==0 || (p->selFlags & SF_Aggregate)!=0 );
if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct ){
p->pGroupBy = sqlite3ExprListDup(db, p->pEList, 0);
pGroupBy = p->pGroupBy;
p->selFlags &= ~SF_Distinct;
}
#endif
/* If there is both a GROUP BY and an ORDER BY clause and they are
** identical, then disable the ORDER BY clause since the GROUP BY
@@ -3904,11 +3907,10 @@ int sqlite3Select(
*/
if( p->selFlags & SF_Distinct ){
KeyInfo *pKeyInfo;
assert( isAgg || pGroupBy );
distinct = pParse->nTab++;
pKeyInfo = keyInfoFromExprList(pParse, p->pEList);
sqlite3VdbeAddOp4(v, OP_OpenEphemeral, distinct, 0, 0,
(char*)pKeyInfo, P4_KEYINFO_HANDOFF);
addrDistinctIndex = sqlite3VdbeAddOp4(v, OP_OpenEphemeral, distinct, 0, 0,
(char*)pKeyInfo, P4_KEYINFO_HANDOFF);
sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
}else{
distinct = -1;
@@ -3916,10 +3918,10 @@ int sqlite3Select(
/* Aggregate and non-aggregate queries are handled differently */
if( !isAgg && pGroupBy==0 ){
/* This case is for non-aggregate queries
** Begin the database scan
*/
pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pOrderBy, 0);
ExprList *pDist = (isDistinct ? p->pEList : 0);
/* Begin the database scan. */
pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pOrderBy, pDist, 0);
if( pWInfo==0 ) goto select_end;
if( pWInfo->nRowOut < p->nSelectRow ) p->nSelectRow = pWInfo->nRowOut;
@@ -3932,10 +3934,47 @@ int sqlite3Select(
p->addrOpenEphm[2] = -1;
}
/* Use the standard inner loop
*/
assert(!isDistinct);
selectInnerLoop(pParse, p, pEList, 0, 0, pOrderBy, -1, pDest,
if( pWInfo->eDistinct ){
assert( isDistinct );
assert( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED
|| pWInfo->eDistinct==WHERE_DISTINCT_UNIQUE
);
distinct = -1;
if( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED ){
int iJump;
int iExpr;
int iFlag = ++pParse->nMem;
int iBase = pParse->nMem+1;
int iBase2 = iBase + pEList->nExpr;
pParse->nMem += (pEList->nExpr*2);
VdbeOp *pOp;
/* Change the OP_OpenEphemeral coded earlier to an OP_Integer. The
** OP_Integer initializes the "first row" flag. */
pOp = sqlite3VdbeGetOp(v, addrDistinctIndex);
pOp->opcode = OP_Integer;
pOp->p1 = 1;
pOp->p2 = iFlag;
sqlite3ExprCodeExprList(pParse, pEList, iBase, 1);
iJump = sqlite3VdbeCurrentAddr(v) + 1 + pEList->nExpr + 1 + 1;
sqlite3VdbeAddOp2(v, OP_If, iFlag, iJump-1);
for(iExpr=0; iExpr<pEList->nExpr; iExpr++){
CollSeq *pColl = sqlite3ExprCollSeq(pParse, pEList->a[iExpr].pExpr);
sqlite3VdbeAddOp3(v, OP_Ne, iBase+iExpr, iJump, iBase2+iExpr);
sqlite3VdbeChangeP4(v, -1, (const char *)pColl, P4_COLLSEQ);
sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
}
sqlite3VdbeAddOp2(v, OP_Goto, 0, pWInfo->iContinue);
sqlite3VdbeAddOp2(v, OP_Integer, 0, iFlag);
assert( sqlite3VdbeCurrentAddr(v)==iJump );
sqlite3VdbeAddOp3(v, OP_Move, iBase, iBase2, pEList->nExpr);
}
}
/* Use the standard inner loop. */
selectInnerLoop(pParse, p, pEList, 0, 0, pOrderBy, distinct, pDest,
pWInfo->iContinue, pWInfo->iBreak);
/* End the database scan loop.
@@ -4045,7 +4084,7 @@ int sqlite3Select(
** in the right order to begin with.
*/
sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pGroupBy, 0);
pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pGroupBy, 0, 0);
if( pWInfo==0 ) goto select_end;
if( pGroupBy==0 ){
/* The optimizer is able to deliver rows in group by order so
@@ -4307,7 +4346,7 @@ int sqlite3Select(
** of output.
*/
resetAccumulator(pParse, &sAggInfo);
pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pMinMax, flag);
pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pMinMax, 0, flag);
if( pWInfo==0 ){
sqlite3ExprListDelete(db, pDel);
goto select_end;