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Commitcdd230d

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Improve planning of OR indexscan plans: for quals like
WHERE (a = 1 or a = 2) and b = 42and an index on (a,b), include the clause b = 42 in the indexqualsgenerated for each arm of the OR clause. Essentially this is an index-driven conversion from CNF to DNF. Implementation is a bit klugy, butbetter than not exploiting the extra quals at all ...
1 parent7c579fa commitcdd230d

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4 files changed

+86
-61
lines changed

4 files changed

+86
-61
lines changed

‎src/backend/optimizer/path/allpaths.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.75 2001/06/0505:26:04 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.76 2001/06/0517:13:51 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -232,7 +232,7 @@ set_plain_rel_pathlist(Query *root, RelOptInfo *rel, RangeTblEntry *rte)
232232
create_index_paths(root,rel);
233233

234234
/* create_index_paths must be done before create_or_index_paths */
235-
create_or_index_paths(root,rel,rel->baserestrictinfo);
235+
create_or_index_paths(root,rel);
236236

237237
/* Now find the cheapest of the paths for this rel */
238238
set_cheapest(rel);

‎src/backend/optimizer/path/indxpath.c

Lines changed: 71 additions & 38 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.105 2001/05/20 20:28:18 tgl Exp $
12+
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.106 2001/06/05 17:13:51 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -397,7 +397,7 @@ match_or_subclause_to_indexkey(RelOptInfo *rel,
397397
clause, false);
398398
}
399399

400-
/*
400+
/*----------
401401
* Given an OR subclause that has previously been determined to match
402402
* the specified index, extract a list of specific opclauses that can be
403403
* used as indexquals.
@@ -406,65 +406,98 @@ match_or_subclause_to_indexkey(RelOptInfo *rel,
406406
* given opclause.However, if the OR subclause is an AND, we have to
407407
* scan it to find the opclause(s) that match the index. (There should
408408
* be at least one, if match_or_subclause_to_indexkey succeeded, but there
409-
* could be more.)Also, we apply expand_indexqual_conditions() to convert
410-
* any special matching opclauses to indexable operators.
409+
* could be more.)
410+
*
411+
* Also, we can look at other restriction clauses of the rel to discover
412+
* additional candidate indexquals: for example, consider
413+
*... where (a = 11 or a = 12) and b = 42;
414+
* If we are dealing with an index on (a,b) then we can include the clause
415+
* b = 42 in the indexqual list generated for each of the OR subclauses.
416+
* Essentially, we are making an index-specific transformation from CNF to
417+
* DNF. (NOTE: when we do this, we end up with a slightly inefficient plan
418+
* because create_indexscan_plan is not very bright about figuring out which
419+
* restriction clauses are implied by the generated indexqual condition.
420+
* Currently we'll end up rechecking both the OR clause and the transferred
421+
* restriction clause as qpquals. FIXME someday.)
422+
*
423+
* Also, we apply expand_indexqual_conditions() to convert any special
424+
* matching opclauses to indexable operators.
411425
*
412426
* The passed-in clause is not changed.
427+
*----------
413428
*/
414429
List*
415430
extract_or_indexqual_conditions(RelOptInfo*rel,
416431
IndexOptInfo*index,
417432
Expr*orsubclause)
418433
{
419434
List*quals=NIL;
435+
int*indexkeys=index->indexkeys;
436+
Oid*classes=index->classlist;
420437

421-
if (and_clause((Node*)orsubclause))
438+
/*
439+
* Extract relevant indexclauses in indexkey order. This is essentially
440+
* just like group_clauses_by_indexkey() except that the input and
441+
* output are lists of bare clauses, not of RestrictInfo nodes.
442+
*/
443+
do
422444
{
445+
intcurIndxKey=indexkeys[0];
446+
OidcurClass=classes[0];
447+
List*clausegroup=NIL;
448+
List*item;
423449

424-
/*
425-
* Extract relevant sub-subclauses in indexkey order. This is
426-
* just like group_clauses_by_indexkey() except that the input and
427-
* output are lists of bare clauses, not of RestrictInfo nodes.
428-
*/
429-
int*indexkeys=index->indexkeys;
430-
Oid*classes=index->classlist;
450+
if (and_clause((Node*)orsubclause))
451+
{
452+
foreach(item,orsubclause->args)
453+
{
454+
Expr*subsubclause= (Expr*)lfirst(item);
431455

432-
do
456+
if (match_clause_to_indexkey(rel,index,
457+
curIndxKey,curClass,
458+
subsubclause, false))
459+
clausegroup=lappend(clausegroup,subsubclause);
460+
}
461+
}
462+
elseif (match_clause_to_indexkey(rel,index,
463+
curIndxKey,curClass,
464+
orsubclause, false))
433465
{
434-
intcurIndxKey=indexkeys[0];
435-
OidcurClass=classes[0];
436-
List*clausegroup=NIL;
437-
List*item;
466+
clausegroup=makeList1(orsubclause);
467+
}
438468

439-
foreach(item,orsubclause->args)
469+
/*
470+
* If we found no clauses for this indexkey in the OR subclause
471+
* itself, try looking in the rel's top-level restriction list.
472+
*/
473+
if (clausegroup==NIL)
474+
{
475+
foreach(item,rel->baserestrictinfo)
440476
{
477+
RestrictInfo*rinfo= (RestrictInfo*)lfirst(item);
478+
441479
if (match_clause_to_indexkey(rel,index,
442480
curIndxKey,curClass,
443-
lfirst(item), false))
444-
clausegroup=lappend(clausegroup,lfirst(item));
481+
rinfo->clause, false))
482+
clausegroup=lappend(clausegroup,rinfo->clause);
445483
}
484+
}
446485

447-
/*
448-
* If no clauses match this key, we're done; we don't want to
449-
* look at keys to its right.
450-
*/
451-
if (clausegroup==NIL)
452-
break;
486+
/*
487+
* If still no clauses match this key, we're done; we don't want to
488+
* look at keys to its right.
489+
*/
490+
if (clausegroup==NIL)
491+
break;
453492

454-
quals=nconc(quals,clausegroup);
493+
quals=nconc(quals,clausegroup);
455494

456-
indexkeys++;
457-
classes++;
458-
}while (!DoneMatchingIndexKeys(indexkeys,index));
495+
indexkeys++;
496+
classes++;
497+
}while (!DoneMatchingIndexKeys(indexkeys,index));
459498

460-
if (quals==NIL)
461-
elog(ERROR,"extract_or_indexqual_conditions: no matching clause");
462-
}
463-
else
464-
{
465-
/* we assume the caller passed a valid indexable qual */
466-
quals=makeList1(orsubclause);
467-
}
499+
if (quals==NIL)
500+
elog(ERROR,"extract_or_indexqual_conditions: no matching clause");
468501

469502
returnexpand_indexqual_conditions(quals);
470503
}

‎src/backend/optimizer/path/orindxpath.c

Lines changed: 11 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/orindxpath.c,v 1.43 2001/05/20 20:28:18 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/orindxpath.c,v 1.44 2001/06/05 17:13:52 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -38,34 +38,31 @@ static void best_or_subclause_index(Query *root, RelOptInfo *rel,
3838
* create_index_paths() must already have been called.
3939
*
4040
* 'rel' is the relation entry for which the paths are to be created
41-
* 'clauses' is the list of available restriction clause nodes
4241
*
4342
* Returns nothing, but adds paths to rel->pathlist via add_path().
4443
*/
4544
void
46-
create_or_index_paths(Query*root,
47-
RelOptInfo*rel,
48-
List*clauses)
45+
create_or_index_paths(Query*root,RelOptInfo*rel)
4946
{
50-
List*clist;
47+
List*rlist;
5148

52-
foreach(clist,clauses)
49+
foreach(rlist,rel->baserestrictinfo)
5350
{
54-
RestrictInfo*clausenode= (RestrictInfo*)lfirst(clist);
51+
RestrictInfo*restrictinfo= (RestrictInfo*)lfirst(rlist);
5552

5653
/*
5754
* Check to see if this clause is an 'or' clause, and, if so,
5855
* whether or not each of the subclauses within the 'or' clause
5956
* has been matched by an index. The information used was saved
6057
* by create_index_paths().
6158
*/
62-
if (restriction_is_or_clause(clausenode)&&
63-
clausenode->subclauseindices)
59+
if (restriction_is_or_clause(restrictinfo)&&
60+
restrictinfo->subclauseindices)
6461
{
6562
boolall_indexable= true;
6663
List*temp;
6764

68-
foreach(temp,clausenode->subclauseindices)
65+
foreach(temp,restrictinfo->subclauseindices)
6966
{
7067
if (lfirst(temp)==NIL)
7168
{
@@ -75,7 +72,6 @@ create_or_index_paths(Query *root,
7572
}
7673
if (all_indexable)
7774
{
78-
7975
/*
8076
* OK, build an IndexPath for this OR clause, using the
8177
* best available index for each subclause.
@@ -93,10 +89,7 @@ create_or_index_paths(Query *root,
9389
*/
9490
pathnode->path.pathkeys=NIL;
9591

96-
/*
97-
* We don't actually care what order the index scans in
98-
* ...
99-
*/
92+
/* We don't actually care what order the index scans in. */
10093
pathnode->indexscandir=NoMovementScanDirection;
10194

10295
/* This isn't a nestloop innerjoin, so: */
@@ -106,8 +99,8 @@ create_or_index_paths(Query *root,
10699

107100
best_or_subclause_indices(root,
108101
rel,
109-
clausenode->clause->args,
110-
clausenode->subclauseindices,
102+
restrictinfo->clause->args,
103+
restrictinfo->subclauseindices,
111104
pathnode);
112105

113106
add_path(rel, (Path*)pathnode);

‎src/include/optimizer/paths.h

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
99
* Portions Copyright (c) 1994, Regents of the University of California
1010
*
11-
* $Id: paths.h,v 1.53 2001/05/20 20:28:20 tgl Exp $
11+
* $Id: paths.h,v 1.54 2001/06/05 17:13:51 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -47,8 +47,7 @@ extern List *expand_indexqual_conditions(List *indexquals);
4747
* orindxpath.c
4848
* additional routines for indexable OR clauses
4949
*/
50-
externvoidcreate_or_index_paths(Query*root,RelOptInfo*rel,
51-
List*clauses);
50+
externvoidcreate_or_index_paths(Query*root,RelOptInfo*rel);
5251

5352
/*
5453
* tidpath.h

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