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Commitf0f3604

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Revert incorrect memory-conservation hack in inheritance_planner().
This reverts commitd1001a7 of 2010-12-05,which was broken as reported by Jeff Davis. The problem is that theindividual planning steps may have side-effects on substructures ofPlannerGlobal, not only the current PlannerInfo root. Arranging to keepall such side effects in the main planning context is probably possible,but it would change this from a quick local hack into a wide-ranging andrather fragile endeavor. Which it's not worth.
1 parent9eacd42 commitf0f3604

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‎src/backend/optimizer/plan/planner.c‎

Lines changed: 15 additions & 53 deletions
Original file line numberDiff line numberDiff line change
@@ -41,7 +41,6 @@
4141
#include"parser/parse_oper.h"
4242
#include"parser/parsetree.h"
4343
#include"utils/lsyscache.h"
44-
#include"utils/memutils.h"
4544
#include"utils/syscache.h"
4645

4746

@@ -742,52 +741,19 @@ inheritance_planner(PlannerInfo *root)
742741
List*rowMarks;
743742
List*tlist;
744743
PlannerInfosubroot;
745-
MemoryContextchildcxt;
746744
ListCell*l;
747745

748-
/*
749-
* Memory management here is a bit messy, because the planning process can
750-
* scribble on both the query parsetree and the rangetable. We need to
751-
* ensure that each call of grouping_planner gets an un-scribbled-on copy
752-
* to start with, so we start by copying the given query tree each time
753-
* (as a byproduct of adjust_appendrel_attrs). However, we also want to
754-
* make sure that the modified rangetable ultimately gets propagated back
755-
* to the master copy, to pick up any changes of the Query structures
756-
* inside subquery RTEs. We do that by copying back the rangetable from
757-
* the first successful child planning step. (We are effectively assuming
758-
* that sub-Queries will get planned identically each time, or at least
759-
* that the impacts on their rangetables will be the same each time.)
760-
*
761-
* Another consideration is that when there are a lot of child tables, we
762-
* can eat a lot of memory this way. To fix that, we create a child
763-
* memory context that can be reset between steps to recover memory, at
764-
* the cost of having to copy the completed plan trees out to the parent
765-
* context.
766-
*/
767-
childcxt=AllocSetContextCreate(CurrentMemoryContext,
768-
"Inheritance child planning context",
769-
ALLOCSET_DEFAULT_MINSIZE,
770-
ALLOCSET_DEFAULT_INITSIZE,
771-
ALLOCSET_DEFAULT_MAXSIZE);
772-
773746
foreach(l,root->append_rel_list)
774747
{
775748
AppendRelInfo*appinfo= (AppendRelInfo*)lfirst(l);
776749
Plan*subplan;
777-
MemoryContextoldcxt;
778750

779751
/* append_rel_list contains all append rels; ignore others */
780752
if (appinfo->parent_relid!=parentRTindex)
781753
continue;
782754

783755
/*
784-
* Discard any cruft generated in previous loop iterations.
785-
*/
786-
MemoryContextReset(childcxt);
787-
oldcxt=MemoryContextSwitchTo(childcxt);
788-
789-
/*
790-
* Generate modified query (in childcxt) with this rel as target.
756+
* Generate modified query with this rel as target.
791757
*/
792758
memcpy(&subroot,root,sizeof(PlannerInfo));
793759
subroot.parse= (Query*)
@@ -801,32 +767,24 @@ inheritance_planner(PlannerInfo *root)
801767
/* and we haven't created PlaceHolderInfos, either */
802768
Assert(subroot.placeholder_list==NIL);
803769

804-
/* Generate plan(also in childcxt)*/
770+
/* Generate plan */
805771
subplan=grouping_planner(&subroot,0.0/* retrieve all tuples */ );
806772

807-
MemoryContextSwitchTo(oldcxt);
808-
809773
/*
810774
* If this child rel was excluded by constraint exclusion, exclude it
811775
* from the plan.
812776
*/
813777
if (is_dummy_plan(subplan))
814778
continue;
815779

816-
/*
817-
* Be sure to copy what we need out of the child context.
818-
*/
819-
subplan=copyObject(subplan);
820-
821-
/* Save rtable from first child to install in parent after the loop */
780+
/* Save rtable from first rel for use below */
822781
if (subplans==NIL)
823-
rtable=copyObject(subroot.parse->rtable);
782+
rtable=subroot.parse->rtable;
824783

825784
subplans=lappend(subplans,subplan);
826785

827786
/* Make sure any initplans from this rel get into the outer list */
828-
root->init_plans=list_concat(root->init_plans,
829-
copyObject(subroot.init_plans));
787+
root->init_plans=list_concat(root->init_plans,subroot.init_plans);
830788

831789
/* Build target-relations list for the executor */
832790
resultRelations=lappend_int(resultRelations,appinfo->child_relid);
@@ -836,18 +794,14 @@ inheritance_planner(PlannerInfo *root)
836794
{
837795
List*rlist;
838796

839-
rlist=copyObject(subroot.parse->returningList);
840797
rlist=set_returning_clause_references(root->glob,
841-
rlist,
798+
subroot.parse->returningList,
842799
subplan,
843800
appinfo->child_relid);
844801
returningLists=lappend(returningLists,rlist);
845802
}
846803
}
847804

848-
/* Done with child context */
849-
MemoryContextDelete(childcxt);
850-
851805
root->resultRelations=resultRelations;
852806

853807
/* Mark result as unordered (probably unnecessary) */
@@ -870,7 +824,15 @@ inheritance_planner(PlannerInfo *root)
870824
}
871825

872826
/*
873-
* Install modified rangetable from first child into parent parsetree.
827+
* Planning might have modified the rangetable, due to changes of the
828+
* Query structures inside subquery RTEs. We have to ensure that this
829+
* gets propagated back to the master copy. But can't do this until we
830+
* are done planning, because all the calls to grouping_planner need
831+
* virgin sub-Queries to work from. (We are effectively assuming that
832+
* sub-Queries will get planned identically each time, or at least that
833+
* the impacts on their rangetables will be the same each time.)
834+
*
835+
* XXX should clean this up someday
874836
*/
875837
parse->rtable=rtable;
876838

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