Many hyperlinks are disabled.
Use anonymous login
to enable hyperlinks.
Overview
| Comment: | Simplify and add invariants to the WhereLoop merging logic inside of whereLoopInsert(). |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | nextgen-query-plan-exp |
| Files: | files | file ages | folders |
| SHA1: |
8f27f35f288434b9e7bc503c608f1e2b |
| User & Date: | drh 2013-06-19 12:34:13.186 |
Context
|
2013-06-19
| ||
| 13:32 | Fix a harmless uninitialized variable warning. (check-in: 9d3ef3bd2c user: drh tags: nextgen-query-plan-exp) | |
| 12:34 | Simplify and add invariants to the WhereLoop merging logic inside of whereLoopInsert(). (check-in: 8f27f35f28 user: drh tags: nextgen-query-plan-exp) | |
| 03:27 | Fix compiler warnings. Fix a harmless off-by-one error in the solver. (check-in: 10021941d0 user: drh tags: nextgen-query-plan-exp) | |
Changes
Changes to src/where.c.
| ︙ | ︙ | |||
4111 4112 4113 4114 4115 4116 4117 |
return SQLITE_OK;
}
/* Search for an existing WhereLoop to overwrite, or which takes
** priority over pTemplate.
*/
for(ppPrev=&pWInfo->pLoops, p=*ppPrev; p; ppPrev=&p->pNextLoop, p=*ppPrev){
| | > > > > > > > > > > > > > > > > | < < < < < < < < < < < < > < < < < < | 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 |
return SQLITE_OK;
}
/* Search for an existing WhereLoop to overwrite, or which takes
** priority over pTemplate.
*/
for(ppPrev=&pWInfo->pLoops, p=*ppPrev; p; ppPrev=&p->pNextLoop, p=*ppPrev){
if( p->iTab!=pTemplate->iTab || p->iSortIdx!=pTemplate->iSortIdx ){
/* If either the iTab or iSortIdx values for two WhereLoop are different
** then those WhereLoops need to be considered separately. Neither is
** a candidate to replace the other. */
continue;
}
/* In the current implementation, the rSetup value is either zero
** or the cost of building an automatic index (NlogN) and the NlogN
** is the same for compatible WhereLoops. */
assert( p->rSetup==0 || pTemplate->rSetup==0
|| p->rSetup==pTemplate->rSetup );
/* whereLoopAddBtree() always generates and inserts the automatic index
** case first. Hence compatible candidate WhereLoops never have a larger
** rSetup. Call this SETUP-INVARIANT */
assert( p->rSetup>=pTemplate->rSetup );
if( (p->prereq & pTemplate->prereq)==p->prereq
&& p->rSetup<=pTemplate->rSetup
&& p->rRun<=pTemplate->rRun
){
/* This branch taken when p is equal or better than pTemplate in
** all of (1) dependences (2) setup-cost, and (3) run-cost. */
assert( p->rSetup==pTemplate->rSetup );
if( p->nLTerm<pTemplate->nLTerm
&& (p->wsFlags & WHERE_INDEXED)!=0
&& (pTemplate->wsFlags & WHERE_INDEXED)!=0
&& p->u.btree.pIndex==pTemplate->u.btree.pIndex
&& p->prereq==pTemplate->prereq
){
/* Overwrite an existing WhereLoop with an similar one that uses
** more terms of the index */
pNext = p->pNextLoop;
break;
}else{
/* pTemplate is not helpful.
** Return without changing or adding anything */
goto whereLoopInsert_noop;
}
}
if( (p->prereq & pTemplate->prereq)==pTemplate->prereq
&& p->rRun>=pTemplate->rRun
&& ALWAYS(p->rSetup>=pTemplate->rSetup) /* See SETUP-INVARIANT above */
){
/* Overwrite an existing WhereLoop with a better one: one that is
** better at one of (1) dependences, (2) setup-cost, or (3) run-cost
** and is no worse in any of those categories. */
pNext = p->pNextLoop;
break;
}
}
/* If we reach this point it means that either p[] should be overwritten
** with pTemplate[] if p[] exists, or if p==NULL then allocate a new
** WhereLoop and insert it.
*/
#if WHERETRACE_ENABLED
|
| ︙ | ︙ |