Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit4c98554

Browse files
committed
Fix ALTER COLUMN TYPE to not open a relation without any lock.
If the column being modified is referenced by a foreign key constraintof another table, ALTER TABLE would open the other table (to re-parsethe constraint's definition) without having first obtained a lock on it.This was evidently intentional, but that doesn't mean it's really safe.It's especially not safe in 9.3, which pre-dates use of MVCC scans forcatalog reads, but even in current releases it doesn't seem like a goodidea.We know we'll need AccessExclusiveLock shortly to drop the obsoletedconstraint, so just get that a little sooner to close the hole.Per testing with a patch that complains if we open a relation withoutholding any lock on it. I don't plan to back-patch that patch, but weshould close the holes it identifies in all supported branches.Discussion:https://postgr.es/m/2038.1538335244@sss.pgh.pa.us
1 parent7871a36 commit4c98554

File tree

1 file changed

+14
-4
lines changed

1 file changed

+14
-4
lines changed

‎src/backend/commands/tablecmds.c

Lines changed: 14 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -9857,8 +9857,7 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
98579857
* appropriate work queue entries. We do this before dropping because in
98589858
* the case of a FOREIGN KEY constraint, we might not yet have exclusive
98599859
* lock on the table the constraint is attached to, and we need to get
9860-
* that before dropping. It's safe because the parser won't actually look
9861-
* at the catalogs to detect the existing entry.
9860+
* that before reparsing/dropping.
98629861
*
98639862
* We can't rely on the output of deparsing to tell us which relation to
98649863
* operate on, because concurrent activity might have made the name
@@ -9874,6 +9873,7 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
98749873
Form_pg_constraintcon;
98759874
Oidrelid;
98769875
Oidconfrelid;
9876+
charcontype;
98779877
boolconislocal;
98789878

98799879
tup=SearchSysCache1(CONSTROID,ObjectIdGetDatum(oldId));
@@ -9890,10 +9890,11 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
98909890
elog(ERROR,"could not identify relation associated with constraint %u",oldId);
98919891
}
98929892
confrelid=con->confrelid;
9893+
contype=con->contype;
98939894
conislocal=con->conislocal;
98949895
ReleaseSysCache(tup);
98959896

9896-
ObjectAddressSet(obj,ConstraintRelationId,lfirst_oid(oid_item));
9897+
ObjectAddressSet(obj,ConstraintRelationId,oldId);
98979898
add_exact_object_address(&obj,objects);
98989899

98999900
/*
@@ -9905,6 +9906,15 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
99059906
if (!conislocal)
99069907
continue;
99079908

9909+
/*
9910+
* When rebuilding an FK constraint that references the table we're
9911+
* modifying, we might not yet have any lock on the FK's table, so get
9912+
* one now. We'll need AccessExclusiveLock for the DROP CONSTRAINT
9913+
* step, so there's no value in asking for anything weaker.
9914+
*/
9915+
if (relid!=tab->relid&&contype==CONSTRAINT_FOREIGN)
9916+
LockRelationOid(relid,AccessExclusiveLock);
9917+
99089918
ATPostAlterTypeParse(oldId,relid,confrelid,
99099919
(char*)lfirst(def_item),
99109920
wqueue,lockmode,tab->rewrite);
@@ -9920,7 +9930,7 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
99209930
(char*)lfirst(def_item),
99219931
wqueue,lockmode,tab->rewrite);
99229932

9923-
ObjectAddressSet(obj,RelationRelationId,lfirst_oid(oid_item));
9933+
ObjectAddressSet(obj,RelationRelationId,oldId);
99249934
add_exact_object_address(&obj,objects);
99259935
}
99269936

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp