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Commit9b27eab

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Fix set_append_rel_pathlist() to deal intelligently with cases where
substituting a child rel's output expressions into the appendrel's restrictionclauses yields a pseudoconstant restriction. We might be able to skip scanningthat child rel entirely (if we get constant FALSE), or generate a one-timefilter. 8.3 more or less accidentally generated plans that weren't completelystupid in these cases, but that was only because an extra recursive level ofsubquery_planner() always occurred and allowed const-simplification to happen.8.4's ability to pull up appendrel members with non-Var outputs exposes thefact that we need to work harder here. Per gripe from Sergey Burladyan.
1 parentbf6570a commit9b27eab

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4 files changed

+114
-58
lines changed

4 files changed

+114
-58
lines changed

‎src/backend/optimizer/path/allpaths.c

Lines changed: 31 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.183 2009/06/11 14:48:58 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.184 2009/07/06 18:26:30 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -29,6 +29,7 @@
2929
#include"optimizer/plancat.h"
3030
#include"optimizer/planner.h"
3131
#include"optimizer/prep.h"
32+
#include"optimizer/restrictinfo.h"
3233
#include"optimizer/var.h"
3334
#include"parser/parse_clause.h"
3435
#include"parser/parsetree.h"
@@ -318,6 +319,8 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
318319
intchildRTindex;
319320
RangeTblEntry*childRTE;
320321
RelOptInfo*childrel;
322+
List*childquals;
323+
Node*childqual;
321324
Path*childpath;
322325
ListCell*parentvars;
323326
ListCell*childvars;
@@ -342,10 +345,34 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
342345
* baserestrictinfo quals are needed before we can check for
343346
* constraint exclusion; so do that first and then check to see if we
344347
* can disregard this child.
348+
*
349+
* As of 8.4, the child rel's targetlist might contain non-Var
350+
* expressions, which means that substitution into the quals
351+
* could produce opportunities for const-simplification, and perhaps
352+
* even pseudoconstant quals. To deal with this, we strip the
353+
* RestrictInfo nodes, do the substitution, do const-simplification,
354+
* and then reconstitute the RestrictInfo layer.
345355
*/
346-
childrel->baserestrictinfo= (List*)
347-
adjust_appendrel_attrs((Node*)rel->baserestrictinfo,
348-
appinfo);
356+
childquals=get_all_actual_clauses(rel->baserestrictinfo);
357+
childquals= (List*)adjust_appendrel_attrs((Node*)childquals,
358+
appinfo);
359+
childqual=eval_const_expressions(root, (Node*)
360+
make_ands_explicit(childquals));
361+
if (childqual&&IsA(childqual,Const)&&
362+
(((Const*)childqual)->constisnull||
363+
!DatumGetBool(((Const*)childqual)->constvalue)))
364+
{
365+
/*
366+
* Restriction reduces to constant FALSE or constant NULL after
367+
* substitution, so this child need not be scanned.
368+
*/
369+
set_dummy_rel_pathlist(childrel);
370+
continue;
371+
}
372+
childquals=make_ands_implicit((Expr*)childqual);
373+
childquals=make_restrictinfos_from_actual_clauses(root,
374+
childquals);
375+
childrel->baserestrictinfo=childquals;
349376

350377
if (relation_excluded_by_constraints(root,childrel,childRTE))
351378
{

‎src/backend/optimizer/prep/prepunion.c

Lines changed: 2 additions & 52 deletions
Original file line numberDiff line numberDiff line change
@@ -22,7 +22,7 @@
2222
*
2323
*
2424
* IDENTIFICATION
25-
* $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.171 2009/06/11 14:48:59 momjian Exp $
25+
* $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.172 2009/07/06 18:26:30 tgl Exp $
2626
*
2727
*-------------------------------------------------------------------------
2828
*/
@@ -1636,57 +1636,7 @@ adjust_appendrel_attrs_mutator(Node *node, AppendRelInfo *context)
16361636
Assert(!IsA(node,SpecialJoinInfo));
16371637
Assert(!IsA(node,AppendRelInfo));
16381638
Assert(!IsA(node,PlaceHolderInfo));
1639-
1640-
/*
1641-
* We have to process RestrictInfo nodes specially.
1642-
*/
1643-
if (IsA(node,RestrictInfo))
1644-
{
1645-
RestrictInfo*oldinfo= (RestrictInfo*)node;
1646-
RestrictInfo*newinfo=makeNode(RestrictInfo);
1647-
1648-
/* Copy all flat-copiable fields */
1649-
memcpy(newinfo,oldinfo,sizeof(RestrictInfo));
1650-
1651-
/* Recursively fix the clause itself */
1652-
newinfo->clause= (Expr*)
1653-
adjust_appendrel_attrs_mutator((Node*)oldinfo->clause,context);
1654-
1655-
/* and the modified version, if an OR clause */
1656-
newinfo->orclause= (Expr*)
1657-
adjust_appendrel_attrs_mutator((Node*)oldinfo->orclause,context);
1658-
1659-
/* adjust relid sets too */
1660-
newinfo->clause_relids=adjust_relid_set(oldinfo->clause_relids,
1661-
context->parent_relid,
1662-
context->child_relid);
1663-
newinfo->required_relids=adjust_relid_set(oldinfo->required_relids,
1664-
context->parent_relid,
1665-
context->child_relid);
1666-
newinfo->left_relids=adjust_relid_set(oldinfo->left_relids,
1667-
context->parent_relid,
1668-
context->child_relid);
1669-
newinfo->right_relids=adjust_relid_set(oldinfo->right_relids,
1670-
context->parent_relid,
1671-
context->child_relid);
1672-
1673-
/*
1674-
* Reset cached derivative fields, since these might need to have
1675-
* different values when considering the child relation.
1676-
*/
1677-
newinfo->eval_cost.startup=-1;
1678-
newinfo->norm_selec=-1;
1679-
newinfo->outer_selec=-1;
1680-
newinfo->left_ec=NULL;
1681-
newinfo->right_ec=NULL;
1682-
newinfo->left_em=NULL;
1683-
newinfo->right_em=NULL;
1684-
newinfo->scansel_cache=NIL;
1685-
newinfo->left_bucketsize=-1;
1686-
newinfo->right_bucketsize=-1;
1687-
1688-
return (Node*)newinfo;
1689-
}
1639+
Assert(!IsA(node,RestrictInfo));
16901640

16911641
/*
16921642
* NOTE: we do not need to recurse into sublinks, because they should

‎src/backend/optimizer/util/restrictinfo.c

Lines changed: 77 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.60 2009/06/11 14:48:59 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.61 2009/07/06 18:26:30 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -271,6 +271,57 @@ make_restrictinfo_from_bitmapqual(Path *bitmapqual,
271271
returnresult;
272272
}
273273

274+
/*
275+
* make_restrictinfos_from_actual_clauses
276+
*
277+
* Given a list of implicitly-ANDed restriction clauses, produce a list
278+
* of RestrictInfo nodes. This is used to reconstitute the RestrictInfo
279+
* representation after doing transformations of a list of clauses.
280+
*
281+
* We assume that the clauses are relation-level restrictions and therefore
282+
* we don't have to worry about is_pushed_down, outerjoin_delayed, or
283+
* nullable_relids (these can be assumed true, false, and NULL, respectively).
284+
* We do take care to recognize pseudoconstant clauses properly.
285+
*/
286+
List*
287+
make_restrictinfos_from_actual_clauses(PlannerInfo*root,
288+
List*clause_list)
289+
{
290+
List*result=NIL;
291+
ListCell*l;
292+
293+
foreach(l,clause_list)
294+
{
295+
Expr*clause= (Expr*)lfirst(l);
296+
boolpseudoconstant;
297+
RestrictInfo*rinfo;
298+
299+
/*
300+
* It's pseudoconstant if it contains no Vars and no volatile
301+
* functions. We probably can't see any sublinks here, so
302+
* contain_var_clause() would likely be enough, but for safety
303+
* use contain_vars_of_level() instead.
304+
*/
305+
pseudoconstant=
306+
!contain_vars_of_level((Node*)clause,0)&&
307+
!contain_volatile_functions((Node*)clause);
308+
if (pseudoconstant)
309+
{
310+
/* tell createplan.c to check for gating quals */
311+
root->hasPseudoConstantQuals= true;
312+
}
313+
314+
rinfo=make_restrictinfo(clause,
315+
true,
316+
false,
317+
pseudoconstant,
318+
NULL,
319+
NULL);
320+
result=lappend(result,rinfo);
321+
}
322+
returnresult;
323+
}
324+
274325
/*
275326
* make_restrictinfo_internal
276327
*
@@ -481,6 +532,31 @@ get_actual_clauses(List *restrictinfo_list)
481532
returnresult;
482533
}
483534

535+
/*
536+
* get_all_actual_clauses
537+
*
538+
* Returns a list containing the bare clauses from 'restrictinfo_list'.
539+
*
540+
* This loses the distinction between regular and pseudoconstant clauses,
541+
* so be careful what you use it for.
542+
*/
543+
List*
544+
get_all_actual_clauses(List*restrictinfo_list)
545+
{
546+
List*result=NIL;
547+
ListCell*l;
548+
549+
foreach(l,restrictinfo_list)
550+
{
551+
RestrictInfo*rinfo= (RestrictInfo*)lfirst(l);
552+
553+
Assert(IsA(rinfo,RestrictInfo));
554+
555+
result=lappend(result,rinfo->clause);
556+
}
557+
returnresult;
558+
}
559+
484560
/*
485561
* extract_actual_clauses
486562
*

‎src/include/optimizer/restrictinfo.h

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/optimizer/restrictinfo.h,v 1.44 2009/05/09 22:51:41 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/optimizer/restrictinfo.h,v 1.45 2009/07/06 18:26:30 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -30,8 +30,11 @@ extern RestrictInfo *make_restrictinfo(Expr *clause,
3030
externList*make_restrictinfo_from_bitmapqual(Path*bitmapqual,
3131
boolis_pushed_down,
3232
boolinclude_predicates);
33+
externList*make_restrictinfos_from_actual_clauses(PlannerInfo*root,
34+
List*clause_list);
3335
externboolrestriction_is_or_clause(RestrictInfo*restrictinfo);
3436
externList*get_actual_clauses(List*restrictinfo_list);
37+
externList*get_all_actual_clauses(List*restrictinfo_list);
3538
externList*extract_actual_clauses(List*restrictinfo_list,
3639
boolpseudoconstant);
3740
externvoidextract_actual_join_clauses(List*restrictinfo_list,

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