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Experiments with the optimization of ORDER BY and GROUP BY clauses.

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FossilOrigin-Name: b150902579d708b454efd5f8750e26a816f7f1a6
This commit is contained in:
drh
2014-03-18 15:30:27 +00:00
parent 0e682099a1
commit 0401acec91
4 changed files with 47 additions and 49 deletions
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72
src/where.c
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@@ -4506,8 +4506,8 @@ static int whereLoopAddVirtual(
pNew->u.vtab.needFree = pIdxInfo->needToFreeIdxStr;
pIdxInfo->needToFreeIdxStr = 0;
pNew->u.vtab.idxStr = pIdxInfo->idxStr;
pNew->u.vtab.isOrdered = (u8)((pIdxInfo->nOrderBy!=0)
&& pIdxInfo->orderByConsumed);
pNew->u.vtab.isOrdered = (i8)(pIdxInfo->orderByConsumed ?
pIdxInfo->nOrderBy : 0);
pNew->rSetup = 0;
pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost);
pNew->nOut = sqlite3LogEst(pIdxInfo->estimatedRows);
@@ -4668,11 +4668,11 @@ static int whereLoopAddAll(WhereLoopBuilder *pBuilder){
/*
** Examine a WherePath (with the addition of the extra WhereLoop of the 5th
** parameters) to see if it outputs rows in the requested ORDER BY
** (or GROUP BY) without requiring a separate sort operation. Return:
** (or GROUP BY) without requiring a separate sort operation. Return N:
**
** 0: ORDER BY is not satisfied. Sorting required
** 1: ORDER BY is satisfied. Omit sorting
** -1: Unknown at this time
** N>0: N terms of the ORDER BY clause are satisfied
** N==0: No terms of the ORDER BY clause are satisfied
** N<0: Unknown yet how many terms of ORDER BY might be satisfied.
**
** Note that processing for WHERE_GROUPBY and WHERE_DISTINCTBY is not as
** strict. With GROUP BY and DISTINCT the only requirement is that
@@ -4682,7 +4682,7 @@ static int whereLoopAddAll(WhereLoopBuilder *pBuilder){
** the pOrderBy terms can be matched in any order. With ORDER BY, the
** pOrderBy terms must be matched in strict left-to-right order.
*/
static int wherePathSatisfiesOrderBy(
static i8 wherePathSatisfiesOrderBy(
WhereInfo *pWInfo, /* The WHERE clause */
ExprList *pOrderBy, /* ORDER BY or GROUP BY or DISTINCT clause to check */
WherePath *pPath, /* The WherePath to check */
@@ -4915,7 +4915,7 @@ static int wherePathSatisfiesOrderBy(
}
}
} /* End the loop over all WhereLoops from outer-most down to inner-most */
if( obSat==obDone ) return 1;
if( obSat==obDone ) return nOrderBy;
if( !isOrderDistinct ) return 0;
return -1;
}
@@ -5001,12 +5001,13 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
** to sqlite3WhereBegin() was concerned about sorting */
rSortCost = 0;
if( pWInfo->pOrderBy==0 || nRowEst==0 ){
aFrom[0].isOrderedValid = 1;
aFrom[0].isOrdered = 0;
}else{
/* TUNING: Estimated cost of sorting is 48*N*log2(N) where N is the
** number of output rows. The 48 is the expected size of a row to sort.
** FIXME: compute a better estimate of the 48 multiplier based on the
** result set expressions. */
aFrom[0].isOrdered = -1;
rSortCost = nRowEst + estLog(nRowEst);
WHERETRACE(0x002,("---- sort cost=%-3d\n", rSortCost));
}
@@ -5020,8 +5021,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
for(pWLoop=pWInfo->pLoops; pWLoop; pWLoop=pWLoop->pNextLoop){
Bitmask maskNew;
Bitmask revMask = 0;
u8 isOrderedValid = pFrom->isOrderedValid;
u8 isOrdered = pFrom->isOrdered;
i8 isOrdered = pFrom->isOrdered;
if( (pWLoop->prereq & ~pFrom->maskLoop)!=0 ) continue;
if( (pWLoop->maskSelf & pFrom->maskLoop)!=0 ) continue;
/* At this point, pWLoop is a candidate to be the next loop.
@@ -5030,21 +5030,12 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
rCost = sqlite3LogEstAdd(rCost, pFrom->rCost);
nOut = pFrom->nRow + pWLoop->nOut;
maskNew = pFrom->maskLoop | pWLoop->maskSelf;
if( !isOrderedValid ){
switch( wherePathSatisfiesOrderBy(pWInfo,
if( isOrdered<0 ){
isOrdered = wherePathSatisfiesOrderBy(pWInfo,
pWInfo->pOrderBy, pFrom, pWInfo->wctrlFlags,
iLoop, pWLoop, &revMask) ){
case 1: /* Yes. pFrom+pWLoop does satisfy the ORDER BY clause */
isOrdered = 1;
isOrderedValid = 1;
break;
case 0: /* No. pFrom+pWLoop will require a separate sort */
isOrdered = 0;
isOrderedValid = 1;
rCost = sqlite3LogEstAdd(rCost, rSortCost);
break;
default: /* Cannot tell yet. Try again on the next iteration */
break;
iLoop, pWLoop, &revMask);
if( isOrdered==0 ){
rCost = sqlite3LogEstAdd(rCost, rSortCost);
}
}else{
revMask = pFrom->revLoop;
@@ -5052,7 +5043,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
/* Check to see if pWLoop should be added to the mxChoice best so far */
for(jj=0, pTo=aTo; jj<nTo; jj++, pTo++){
if( pTo->maskLoop==maskNew
&& pTo->isOrderedValid==isOrderedValid
&& ((pTo->isOrdered^isOrdered)&80)==0
&& ((pTo->rCost<=rCost && pTo->nRow<=nOut) ||
(pTo->rCost>=rCost && pTo->nRow>=nOut))
){
@@ -5066,7 +5057,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
if( sqlite3WhereTrace&0x4 ){
sqlite3DebugPrintf("Skip %s cost=%-3d,%3d order=%c\n",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
isOrdered>=0 ? isOrdered+'0' : '?');
}
#endif
continue;
@@ -5084,7 +5075,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
if( sqlite3WhereTrace&0x4 ){
sqlite3DebugPrintf("New %s cost=%-3d,%3d order=%c\n",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
isOrdered>=0 ? isOrdered+'0' : '?');
}
#endif
}else{
@@ -5094,10 +5085,10 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
sqlite3DebugPrintf(
"Skip %s cost=%-3d,%3d order=%c",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
isOrdered>=0 ? isOrdered+'0' : '?');
sqlite3DebugPrintf(" vs %s cost=%-3d,%d order=%c\n",
wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
pTo->isOrdered>=0 ? pTo->isOrdered+'0' : '?');
}
#endif
testcase( pTo->rCost==rCost );
@@ -5110,10 +5101,10 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
sqlite3DebugPrintf(
"Update %s cost=%-3d,%3d order=%c",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
isOrdered>=0 ? isOrdered+'0' : '?');
sqlite3DebugPrintf(" was %s cost=%-3d,%3d order=%c\n",
wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
pTo->isOrdered>=0 ? pTo->isOrdered+'0' : '?');
}
#endif
}
@@ -5122,7 +5113,6 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
pTo->revLoop = revMask;
pTo->nRow = nOut;
pTo->rCost = rCost;
pTo->isOrderedValid = isOrderedValid;
pTo->isOrdered = isOrdered;
memcpy(pTo->aLoop, pFrom->aLoop, sizeof(WhereLoop*)*iLoop);
pTo->aLoop[iLoop] = pWLoop;
@@ -5147,8 +5137,8 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
for(ii=0, pTo=aTo; ii<nTo; ii++, pTo++){
sqlite3DebugPrintf(" %s cost=%-3d nrow=%-3d order=%c",
wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
if( pTo->isOrderedValid && pTo->isOrdered ){
pTo->isOrdered>=0 ? (pTo->isOrdered+'0') : '?');
if( pTo->isOrdered>0 ){
sqlite3DebugPrintf(" rev=0x%llx\n", pTo->revLoop);
}else{
sqlite3DebugPrintf("\n");
@@ -5191,9 +5181,11 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
Bitmask notUsed;
int rc = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pResultSet, pFrom,
WHERE_DISTINCTBY, nLoop-1, pFrom->aLoop[nLoop-1], &notUsed);
if( rc==1 ) pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
if( rc==pWInfo->pResultSet->nExpr ){
pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
}
}
if( pFrom->isOrdered ){
if( pWInfo->pOrderBy && pFrom->isOrdered==pWInfo->pOrderBy->nExpr ){
if( pWInfo->wctrlFlags & WHERE_DISTINCTBY ){
pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
}else{
@@ -5386,7 +5378,7 @@ WhereInfo *sqlite3WhereBegin(
Parse *pParse, /* The parser context */
SrcList *pTabList, /* FROM clause: A list of all tables to be scanned */
Expr *pWhere, /* The WHERE clause */
ExprList *pOrderBy, /* An ORDER BY clause, or NULL */
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 */
@@ -5408,6 +5400,10 @@ WhereInfo *sqlite3WhereBegin(
/* Variable initialization */
db = pParse->db;
memset(&sWLB, 0, sizeof(sWLB));
/* An ORDER/GROUP BY clause of more than 63 terms cannot be optimized */
testcase( pOrderBy && pOrderBy->nExpr==BMS-1 );
if( pOrderBy && pOrderBy->nExpr>=BMS ) pOrderBy = 0;
sWLB.pOrderBy = pOrderBy;
/* Disable the DISTINCT optimization if SQLITE_DistinctOpt is set via