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Commit4353bc8

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Disallow converting an inheritance child table to a view.
Generally, members of inheritance trees must be plain tables (or,in more recent versions, foreign tables). ALTER TABLE INHERITrejects creating an inheritance relationship that has a view ateither end. When DefineQueryRewrite attempts to convert a relationto a view, it already had checks prohibiting doing so for partitioningparents or children as well as traditional-inheritance parents ...but it neglected to check that a traditional-inheritance child wasn'tbeing converted. Since the planner assumes that any inheritancechild is a table, this led to making plans that tried to do a physicalscan on a view, causing failures (or even crashes, in recent versions).One could imagine trying to support such a case by expanding the viewnormally, but since the rewriter runs before the planner doesinheritance expansion, it would take some very fundamental refactoringto make that possible. There are probably a lot of other parts of thesystem that don't cope well with such a situation, too. For now,just forbid it.Per bug #16856 from Yang Lin. Back-patch to all supported branches.(In versions before v10, this includes back-patching the portion ofcommit501ed02 that added has_superclass(). Perhaps the lack ofthat infrastructure partially explains the missing check.)Discussion:https://postgr.es/m/16856-0363e05c6e1612fd@postgresql.org
1 parent8050931 commit4353bc8

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4 files changed

+52
-16
lines changed

4 files changed

+52
-16
lines changed

‎src/backend/catalog/pg_inherits.c

Lines changed: 7 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -3,8 +3,8 @@
33
* pg_inherits.c
44
* routines to support manipulation of the pg_inherits relation
55
*
6-
* Note: currently, this moduleonly contains inquiry functions; the actual
7-
* creation and deletion of pg_inherits entries is done in tablecmds.c.
6+
* Note: currently, this modulemostly contains inquiry functions; actual
7+
* creation and deletion of pg_inherits entries ismostlydone in tablecmds.c.
88
* Perhaps someday that code should be moved here, but it'd have to be
99
* disentangled from other stuff such as pg_depend updates.
1010
*
@@ -278,9 +278,11 @@ has_subclass(Oid relationId)
278278
}
279279

280280
/*
281-
* has_superclass - does this relation inherit from another? The caller
282-
* should hold a lock on the given relation so that it can't be concurrently
283-
* added to or removed from an inheritance hierarchy.
281+
* has_superclass - does this relation inherit from another?
282+
*
283+
* Unlike has_subclass, this can be relied on to give an accurate answer.
284+
* However, the caller must hold a lock on the given relation so that it
285+
* can't be concurrently added to or removed from an inheritance hierarchy.
284286
*/
285287
bool
286288
has_superclass(OidrelationId)

‎src/backend/rewrite/rewriteDefine.c

Lines changed: 18 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -26,6 +26,7 @@
2626
#include"catalog/indexing.h"
2727
#include"catalog/namespace.h"
2828
#include"catalog/objectaccess.h"
29+
#include"catalog/pg_inherits.h"
2930
#include"catalog/pg_rewrite.h"
3031
#include"catalog/storage.h"
3132
#include"commands/policy.h"
@@ -413,13 +414,14 @@ DefineQueryRewrite(const char *rulename,
413414
* Are we converting a relation to a view?
414415
*
415416
* If so, check that the relation is empty because the storage for the
416-
* relation is going to be deleted. Also insist that the rel not have
417-
* any triggers, indexes, child tables, policies, or RLS enabled.
418-
* (Note: these tests are too strict, because they will reject
419-
* relations that once had such but don't anymore. But we don't
420-
* really care, because this whole business of converting relations to
421-
* views is just a kluge to allow dump/reload of views that
422-
* participate in circular dependencies.)
417+
* relation is going to be deleted. Also insist that the rel not be
418+
* involved in partitioning, nor have any triggers, indexes, child or
419+
* parent tables, RLS policies, or RLS enabled. (Note: some of these
420+
* tests are too strict, because they will reject relations that once
421+
* had such but don't anymore. But we don't really care, because this
422+
* whole business of converting relations to views is just an obsolete
423+
* kluge to allow dump/reload of views that participate in circular
424+
* dependencies.)
423425
*/
424426
if (event_relation->rd_rel->relkind!=RELKIND_VIEW&&
425427
event_relation->rd_rel->relkind!=RELKIND_MATVIEW)
@@ -434,6 +436,9 @@ DefineQueryRewrite(const char *rulename,
434436
errmsg("cannot convert partitioned table \"%s\" to a view",
435437
RelationGetRelationName(event_relation))));
436438

439+
/* only case left: */
440+
Assert(event_relation->rd_rel->relkind==RELKIND_RELATION);
441+
437442
if (event_relation->rd_rel->relispartition)
438443
ereport(ERROR,
439444
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -471,6 +476,12 @@ DefineQueryRewrite(const char *rulename,
471476
errmsg("could not convert table \"%s\" to a view because it has child tables",
472477
RelationGetRelationName(event_relation))));
473478

479+
if (has_superclass(RelationGetRelid(event_relation)))
480+
ereport(ERROR,
481+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
482+
errmsg("could not convert table \"%s\" to a view because it has parent tables",
483+
RelationGetRelationName(event_relation))));
484+
474485
if (event_relation->rd_rel->relrowsecurity)
475486
ereport(ERROR,
476487
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),

‎src/test/regress/expected/rules.out

Lines changed: 13 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -2758,16 +2758,27 @@ select reltoastrelid, relkind, relfrozenxid
27582758
(1 row)
27592759

27602760
drop view rules_fooview;
2761-
-- trying to convert a partitioned table to view is not allowed
2761+
-- cannot convert an inheritance parent or child to a view, though
2762+
create table rules_fooview (x int, y text);
2763+
create table rules_fooview_child () inherits (rules_fooview);
2764+
create rule "_RETURN" as on select to rules_fooview do instead
2765+
select 1 as x, 'aaa'::text as y;
2766+
ERROR: could not convert table "rules_fooview" to a view because it has child tables
2767+
create rule "_RETURN" as on select to rules_fooview_child do instead
2768+
select 1 as x, 'aaa'::text as y;
2769+
ERROR: could not convert table "rules_fooview_child" to a view because it has parent tables
2770+
drop table rules_fooview cascade;
2771+
NOTICE: drop cascades to table rules_fooview_child
2772+
-- likewise, converting a partitioned table or partition to view is not allowed
27622773
create table rules_fooview (x int, y text) partition by list (x);
27632774
create rule "_RETURN" as on select to rules_fooview do instead
27642775
select 1 as x, 'aaa'::text as y;
27652776
ERROR: cannot convert partitioned table "rules_fooview" to a view
2766-
-- nor can one convert a partition to view
27672777
create table rules_fooview_part partition of rules_fooview for values in (1);
27682778
create rule "_RETURN" as on select to rules_fooview_part do instead
27692779
select 1 as x, 'aaa'::text as y;
27702780
ERROR: cannot convert partition "rules_fooview_part" to a view
2781+
drop table rules_fooview;
27712782
--
27722783
-- check for planner problems with complex inherited UPDATES
27732784
--

‎src/test/regress/sql/rules.sql

Lines changed: 14 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -901,16 +901,28 @@ select reltoastrelid, relkind, relfrozenxid
901901

902902
dropview rules_fooview;
903903

904-
-- trying to convert a partitioned table to view is not allowed
904+
-- cannot convert an inheritance parent or child to a view, though
905+
createtablerules_fooview (xint, ytext);
906+
createtablerules_fooview_child () inherits (rules_fooview);
907+
908+
createrule "_RETURN"asonselect to rules_fooview do instead
909+
select1as x,'aaa'::textas y;
910+
createrule "_RETURN"asonselect to rules_fooview_child do instead
911+
select1as x,'aaa'::textas y;
912+
913+
droptable rules_fooview cascade;
914+
915+
-- likewise, converting a partitioned table or partition to view is not allowed
905916
createtablerules_fooview (xint, ytext) partition by list (x);
906917
createrule "_RETURN"asonselect to rules_fooview do instead
907918
select1as x,'aaa'::textas y;
908919

909-
-- nor can one convert a partition to view
910920
createtablerules_fooview_part partition of rules_fooview forvaluesin (1);
911921
createrule "_RETURN"asonselect to rules_fooview_part do instead
912922
select1as x,'aaa'::textas y;
913923

924+
droptable rules_fooview;
925+
914926
--
915927
-- check for planner problems with complex inherited UPDATES
916928
--

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