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When planning a query using sorting, resolve ties in the solver by selecting

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loop plans with the smaller unsorted cost.

FossilOrigin-Name: f261678c90297f9767040c577796cc1d4db598aa44b0de6906cb73eaef377dee
This commit is contained in:
drh
2017-05-22 00:45:15 +00:00
parent e46515b53f
commit 78436d4c66
3 changed files with 33 additions and 22 deletions
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40
src/where.c
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@@ -4003,8 +4003,8 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
** this candidate as not viable. */
#ifdef WHERETRACE_ENABLED /* 0x4 */
if( sqlite3WhereTrace&0x4 ){
sqlite3DebugPrintf("Skip %s cost=%-3d,%3d order=%c\n",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
sqlite3DebugPrintf("Skip %s cost=%-3d,%3d,%3d order=%c\n",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut, rUnsorted,
isOrdered>=0 ? isOrdered+'0' : '?');
}
#endif
@@ -4022,26 +4022,36 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
pTo = &aTo[jj];
#ifdef WHERETRACE_ENABLED /* 0x4 */
if( sqlite3WhereTrace&0x4 ){
sqlite3DebugPrintf("New %s cost=%-3d,%3d order=%c\n",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
sqlite3DebugPrintf("New %s cost=%-3d,%3d,%3d order=%c\n",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut, rUnsorted,
isOrdered>=0 ? isOrdered+'0' : '?');
}
#endif
}else{
/* Control reaches here if best-so-far path pTo=aTo[jj] covers the
** same set of loops and has the sam isOrdered setting as the
** same set of loops and has the same isOrdered setting as the
** candidate path. Check to see if the candidate should replace
** pTo or if the candidate should be skipped */
if( pTo->rCost<rCost || (pTo->rCost==rCost && pTo->nRow<=nOut) ){
** pTo or if the candidate should be skipped.
**
** The conditional is an expanded vector comparison equivalent to:
** (pTo->rCost,pTo->nRow,pTo->rUnsorted) <= (rCost,nOut,rUnsorted)
*/
if( pTo->rCost<rCost
|| (pTo->rCost==rCost
&& (pTo->nRow<nOut
|| (pTo->nRow==nOut && pTo->rUnsorted<=rUnsorted)
)
)
){
#ifdef WHERETRACE_ENABLED /* 0x4 */
if( sqlite3WhereTrace&0x4 ){
sqlite3DebugPrintf(
"Skip %s cost=%-3d,%3d order=%c",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
"Skip %s cost=%-3d,%3d,%3d order=%c",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut, rUnsorted,
isOrdered>=0 ? isOrdered+'0' : '?');
sqlite3DebugPrintf(" vs %s cost=%-3d,%d order=%c\n",
sqlite3DebugPrintf(" vs %s cost=%-3d,%3d,%3d order=%c\n",
wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
pTo->isOrdered>=0 ? pTo->isOrdered+'0' : '?');
pTo->rUnsorted, pTo->isOrdered>=0 ? pTo->isOrdered+'0' : '?');
}
#endif
/* Discard the candidate path from further consideration */
@@ -4054,12 +4064,12 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
#ifdef WHERETRACE_ENABLED /* 0x4 */
if( sqlite3WhereTrace&0x4 ){
sqlite3DebugPrintf(
"Update %s cost=%-3d,%3d order=%c",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
"Update %s cost=%-3d,%3d,%3d order=%c",
wherePathName(pFrom, iLoop, pWLoop), rCost, nOut, rUnsorted,
isOrdered>=0 ? isOrdered+'0' : '?');
sqlite3DebugPrintf(" was %s cost=%-3d,%3d order=%c\n",
sqlite3DebugPrintf(" was %s cost=%-3d,%3d,%3d order=%c\n",
wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
pTo->isOrdered>=0 ? pTo->isOrdered+'0' : '?');
pTo->rUnsorted, pTo->isOrdered>=0 ? pTo->isOrdered+'0' : '?');
}
#endif
}