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Commitdd705a0

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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 parentf740082 commitdd705a0

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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
*
@@ -277,9 +277,11 @@ has_subclass(Oid relationId)
277277
}
278278

279279
/*
280-
* has_superclass - does this relation inherit from another? The caller
281-
* should hold a lock on the given relation so that it can't be concurrently
282-
* added to or removed from an inheritance hierarchy.
280+
* has_superclass - does this relation inherit from another?
281+
*
282+
* Unlike has_subclass, this can be relied on to give an accurate answer.
283+
* However, the caller must hold a lock on the given relation so that it
284+
* can't be concurrently added to or removed from an inheritance hierarchy.
283285
*/
284286
bool
285287
has_superclass(OidrelationId)

‎src/backend/rewrite/rewriteDefine.c

Lines changed: 18 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -25,6 +25,7 @@
2525
#include"catalog/heap.h"
2626
#include"catalog/namespace.h"
2727
#include"catalog/objectaccess.h"
28+
#include"catalog/pg_inherits.h"
2829
#include"catalog/pg_rewrite.h"
2930
#include"catalog/storage.h"
3031
#include"commands/policy.h"
@@ -412,13 +413,14 @@ DefineQueryRewrite(const char *rulename,
412413
* Are we converting a relation to a view?
413414
*
414415
* If so, check that the relation is empty because the storage for the
415-
* relation is going to be deleted. Also insist that the rel not have
416-
* any triggers, indexes, child tables, policies, or RLS enabled.
417-
* (Note: these tests are too strict, because they will reject
418-
* relations that once had such but don't anymore. But we don't
419-
* really care, because this whole business of converting relations to
420-
* views is just a kluge to allow dump/reload of views that
421-
* participate in circular dependencies.)
416+
* relation is going to be deleted. Also insist that the rel not be
417+
* involved in partitioning, nor have any triggers, indexes, child or
418+
* parent tables, RLS policies, or RLS enabled. (Note: some of these
419+
* tests are too strict, because they will reject relations that once
420+
* had such but don't anymore. But we don't really care, because this
421+
* whole business of converting relations to views is just an obsolete
422+
* kluge to allow dump/reload of views that participate in circular
423+
* dependencies.)
422424
*/
423425
if (event_relation->rd_rel->relkind!=RELKIND_VIEW&&
424426
event_relation->rd_rel->relkind!=RELKIND_MATVIEW)
@@ -433,6 +435,9 @@ DefineQueryRewrite(const char *rulename,
433435
errmsg("cannot convert partitioned table \"%s\" to a view",
434436
RelationGetRelationName(event_relation))));
435437

438+
/* only case left: */
439+
Assert(event_relation->rd_rel->relkind==RELKIND_RELATION);
440+
436441
if (event_relation->rd_rel->relispartition)
437442
ereport(ERROR,
438443
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -470,6 +475,12 @@ DefineQueryRewrite(const char *rulename,
470475
errmsg("could not convert table \"%s\" to a view because it has child tables",
471476
RelationGetRelationName(event_relation))));
472477

478+
if (has_superclass(RelationGetRelid(event_relation)))
479+
ereport(ERROR,
480+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
481+
errmsg("could not convert table \"%s\" to a view because it has parent tables",
482+
RelationGetRelationName(event_relation))));
483+
473484
if (event_relation->rd_rel->relrowsecurity)
474485
ereport(ERROR,
475486
(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
@@ -2801,16 +2801,27 @@ select reltoastrelid, relkind, relfrozenxid
28012801
(1 row)
28022802

28032803
drop view rules_fooview;
2804-
-- trying to convert a partitioned table to view is not allowed
2804+
-- cannot convert an inheritance parent or child to a view, though
2805+
create table rules_fooview (x int, y text);
2806+
create table rules_fooview_child () inherits (rules_fooview);
2807+
create rule "_RETURN" as on select to rules_fooview do instead
2808+
select 1 as x, 'aaa'::text as y;
2809+
ERROR: could not convert table "rules_fooview" to a view because it has child tables
2810+
create rule "_RETURN" as on select to rules_fooview_child do instead
2811+
select 1 as x, 'aaa'::text as y;
2812+
ERROR: could not convert table "rules_fooview_child" to a view because it has parent tables
2813+
drop table rules_fooview cascade;
2814+
NOTICE: drop cascades to table rules_fooview_child
2815+
-- likewise, converting a partitioned table or partition to view is not allowed
28052816
create table rules_fooview (x int, y text) partition by list (x);
28062817
create rule "_RETURN" as on select to rules_fooview do instead
28072818
select 1 as x, 'aaa'::text as y;
28082819
ERROR: cannot convert partitioned table "rules_fooview" to a view
2809-
-- nor can one convert a partition to view
28102820
create table rules_fooview_part partition of rules_fooview for values in (1);
28112821
create rule "_RETURN" as on select to rules_fooview_part do instead
28122822
select 1 as x, 'aaa'::text as y;
28132823
ERROR: cannot convert partition "rules_fooview_part" to a view
2824+
drop table rules_fooview;
28142825
--
28152826
-- check for planner problems with complex inherited UPDATES
28162827
--

‎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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