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Use TRUNCATE to preserve relfilenode for pg_largeobject + index.

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Commit 9a974cbcba arranged to preserve
the relfilenode of user tables across pg_upgrade, but failed to notice
that pg_upgrade treats pg_largeobject as a user table and thus it needs
the same treatment. Otherwise, large objects will appear to vanish
after a  pg_upgrade.

Commit d498e052b4 fixed this problem
by teaching pg_dump to UPDATE pg_class.relfilenode for pg_largeobject
and its index. However, because an UPDATE on the catalog rows doesn't
change anything on disk, this can leave stray files behind in the new
cluster. They will normally be empty, but it's a little bit untidy.

Hence, this commit arranges to do the same thing using DDL. Specifically,
it makes TRUNCATE work for the pg_largeobject catalog when in
binary-upgrade mode, and it then uses that command in binary-upgrade
dumps as a way of setting pg_class.relfilenode for pg_largeobject and
its index. That way, the old files are removed from the new cluster.

Discussion: http://postgr.es/m/CA+TgmoYYMXGUJO5GZk1-MByJGu_bB8CbOL6GJQC8=Bzt6x6vDg@mail.gmail.com
This commit is contained in:
Robert Haas
2022-07-28 15:32:24 -04:00
parent 02e5c273a2
commit 4ab5dae947
4 changed files with 120 additions and 15 deletions
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11
src/backend/commands/tablecmds.c
View File

@ -40,6 +40,7 @@
#include "catalog/pg_depend.h"
#include "catalog/pg_foreign_table.h"
#include "catalog/pg_inherits.h"
#include "catalog/pg_largeobject.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_statistic_ext.h"
@ -2181,7 +2182,15 @@ truncate_check_rel(Oid relid, Form_pg_class reltuple)
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("\"%s\" is not a table", relname)));
if (!allowSystemTableMods && IsSystemClass(relid, reltuple))
/*
* Most system catalogs can't be truncated at all, or at least not unless
* allow_system_table_mods=on. As an exception, however, we allow
* pg_largeobject to be truncated as part of pg_upgrade, because we need
* to change its relfilenode to match the old cluster, and allowing a
* TRUNCATE command to be executed is the easiest way of doing that.
*/
if (!allowSystemTableMods && IsSystemClass(relid, reltuple)
&& (!IsBinaryUpgrade || relid != LargeObjectRelationId))
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied: \"%s\" is a system catalog",