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Take the LIMIT clause into account when estimating the cost of sorting.

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FossilOrigin-Name: d491745cab951e0de70f1f79b7640ea8aff6e8bb
This commit is contained in:
drh
2016-02-25 16:04:59 +00:00
parent d8c22ac655
commit c3489bbf77
7 changed files with 93 additions and 59 deletions
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44
src/where.c
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@@ -31,8 +31,8 @@ static int whereLoopResize(sqlite3*, WhereLoop*, int);
/*
** Return the estimated number of output rows from a WHERE clause
*/
u64 sqlite3WhereOutputRowCount(WhereInfo *pWInfo){
return sqlite3LogEstToInt(pWInfo->nRowOut);
LogEst sqlite3WhereOutputRowCount(WhereInfo *pWInfo){
return pWInfo->nRowOut;
}
/*
@@ -3438,6 +3438,7 @@ static const char *wherePathName(WherePath *pPath, int nLoop, WhereLoop *pLast){
** order.
*/
static LogEst whereSortingCost(
WhereInfo *pWInfo,
LogEst nRow,
int nOrderBy,
int nSorted
@@ -3458,7 +3459,15 @@ static LogEst whereSortingCost(
LogEst rScale, rSortCost;
assert( nOrderBy>0 && 66==sqlite3LogEst(100) );
rScale = sqlite3LogEst((nOrderBy-nSorted)*100/nOrderBy) - 66;
rSortCost = nRow + estLog(nRow) + rScale + 16;
rSortCost = nRow + rScale + 16;
/* Multiple by log(M) where M is the number of output rows.
** Use the LIMIT for M if it is smaller */
if( (pWInfo->wctrlFlags & WHERE_USE_LIMIT)!=0 ){
LogEst m = sqlite3LogEst(pWInfo->iLimit);
if( m<nRow ) nRow = m;
}
rSortCost += estLog(nRow);
return rSortCost;
}
@@ -3592,7 +3601,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
if( isOrdered>=0 && isOrdered<nOrderBy ){
if( aSortCost[isOrdered]==0 ){
aSortCost[isOrdered] = whereSortingCost(
nRowEst, nOrderBy, isOrdered
pWInfo, nRowEst, nOrderBy, isOrdered
);
}
rCost = sqlite3LogEstAdd(rUnsorted, aSortCost[isOrdered]);
@@ -3991,7 +4000,8 @@ WhereInfo *sqlite3WhereBegin(
ExprList *pOrderBy, /* An ORDER BY (or GROUP BY) clause, or NULL */
ExprList *pResultSet, /* Result set of the query */
u16 wctrlFlags, /* One of the WHERE_* flags defined in sqliteInt.h */
int iIdxCur /* If WHERE_ONETABLE_ONLY is set, index cursor number */
int iAuxArg /* If WHERE_ONETABLE_ONLY is set, index cursor number,
** If WHERE_USE_LIMIT, then the limit amount */
){
int nByteWInfo; /* Num. bytes allocated for WhereInfo struct */
int nTabList; /* Number of elements in pTabList */
@@ -4012,6 +4022,10 @@ WhereInfo *sqlite3WhereBegin(
&& (wctrlFlags & WHERE_OMIT_OPEN_CLOSE)==0
));
/* Only one of WHERE_ONETABLE_ONLY or WHERE_USE_LIMIT */
assert( (wctrlFlags & WHERE_ONETABLE_ONLY)==0
|| (wctrlFlags & WHERE_USE_LIMIT)==0 );
/* Variable initialization */
db = pParse->db;
memset(&sWLB, 0, sizeof(sWLB));
@@ -4065,6 +4079,7 @@ WhereInfo *sqlite3WhereBegin(
pWInfo->pResultSet = pResultSet;
pWInfo->iBreak = pWInfo->iContinue = sqlite3VdbeMakeLabel(v);
pWInfo->wctrlFlags = wctrlFlags;
pWInfo->iLimit = iAuxArg;
pWInfo->savedNQueryLoop = pParse->nQueryLoop;
assert( pWInfo->eOnePass==ONEPASS_OFF ); /* ONEPASS defaults to OFF */
pMaskSet = &pWInfo->sMaskSet;
@@ -4145,9 +4160,14 @@ WhereInfo *sqlite3WhereBegin(
}
/* Construct the WhereLoop objects */
WHERETRACE(0xffff,("*** Optimizer Start *** (wctrlFlags: 0x%x)\n",
wctrlFlags));
#if defined(WHERETRACE_ENABLED)
if( sqlite3WhereTrace & 0xffff ){
sqlite3DebugPrintf("*** Optimizer Start *** (wctrlFlags: 0x%x",wctrlFlags);
if( wctrlFlags & WHERE_USE_LIMIT ){
sqlite3DebugPrintf(", limit: %d", iAuxArg);
}
sqlite3DebugPrintf(")\n");
}
if( sqlite3WhereTrace & 0x100 ){ /* Display all terms of the WHERE clause */
int i;
for(i=0; i<sWLB.pWC->nTerm; i++){
@@ -4330,8 +4350,8 @@ WhereInfo *sqlite3WhereBegin(
Index *pIx = pLoop->u.btree.pIndex;
int iIndexCur;
int op = OP_OpenRead;
/* iIdxCur is always set if to a positive value if ONEPASS is possible */
assert( iIdxCur!=0 || (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0 );
/* iAuxArg is always set if to a positive value if ONEPASS is possible */
assert( iAuxArg!=0 || (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0 );
if( !HasRowid(pTab) && IsPrimaryKeyIndex(pIx)
&& (wctrlFlags & WHERE_ONETABLE_ONLY)!=0
){
@@ -4341,7 +4361,7 @@ WhereInfo *sqlite3WhereBegin(
op = 0;
}else if( pWInfo->eOnePass!=ONEPASS_OFF ){
Index *pJ = pTabItem->pTab->pIndex;
iIndexCur = iIdxCur;
iIndexCur = iAuxArg;
assert( wctrlFlags & WHERE_ONEPASS_DESIRED );
while( ALWAYS(pJ) && pJ!=pIx ){
iIndexCur++;
@@ -4349,8 +4369,8 @@ WhereInfo *sqlite3WhereBegin(
}
op = OP_OpenWrite;
pWInfo->aiCurOnePass[1] = iIndexCur;
}else if( iIdxCur && (wctrlFlags & WHERE_ONETABLE_ONLY)!=0 ){
iIndexCur = iIdxCur;
}else if( iAuxArg && (wctrlFlags & WHERE_ONETABLE_ONLY)!=0 ){
iIndexCur = iAuxArg;
if( wctrlFlags & WHERE_REOPEN_IDX ) op = OP_ReopenIdx;
}else{
iIndexCur = pParse->nTab++;