Horton

Re: race condition in pg_class

Grigory Smolkin <smallkeen@gmail.com>

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From: Smolkin Grigory <smallkeen@gmail.com>
To: pgsql-hackers@postgresql.org
Date: 2023-10-26T09:52:41Z
Lists: pgsql-hackers

Commits

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  1. Replace tests of ALTER DATABASE RESET TABLESPACE.

  2. meson: Flush stdout in testwrap

  3. Fix catcache invalidation of a list entry that's being built

  4. Stop reading uninitialized memory in heap_inplace_lock().

  5. Fix use of uninitialized value in previous commit.

  6. Back-patch "Refactor code in tablecmds.c to check and process tablespace moves"

  7. Fix data loss at inplace update after heap_update().

  8. For inplace update durability, make heap_update() callers wait.

  9. Warn if LOCKTAG_TUPLE is held at commit, under debug_assertions.

  10. Don't lose partitioned table reltuples=0 after relhassubclass=f.

  11. Fix new assertion for MERGE view_name ... DO NOTHING.

  12. Remove configuration-dependent output from new inplace-inval test.

  13. AccessExclusiveLock new relations just after assigning the OID.

  14. Cope with inplace update making catcache stale during TOAST fetch.

  15. Expand comments and add an assertion in nodeModifyTable.c.

  16. Improve test coverage for changes to inplace-updated catalogs.

  17. Lock before setting relhassubclass on RELKIND_PARTITIONED_INDEX.

  18. Lock owned sequences during ALTER TABLE SET { LOGGED | UNLOGGED }.

  19. Make TAP todo_start effects the same under Meson and prove_check.

  20. Add an injection_points isolation test suite.

  21. Add wait event type "InjectionPoint", a custom type like "Extension".

  22. Create waitfuncs.c for pg_isolation_test_session_is_blocked().

  23. Rework planning and execution of UPDATE and DELETE.

> ALTER TABLE ADD CONSTRAINT would certainly have taken
> AccessExclusiveLock on the "example" table, which should be sufficient
> to prevent anything else from touching its pg_class row.  The only
> mechanism I can think of that might bypass that is a manual UPDATE on
> pg_class, which would just manipulate the row as a row without concern
> for associated relation-level locks.  Any chance that somebody was
> doing something like that?

No chance. Our infrastructure dont do that, and users dont just have the
privileges to mess with pg_catalog.

ср, 25 окт. 2023 г. в 21:06, Tom Lane <tgl@sss.pgh.pa.us>:

> Smolkin Grigory <smallkeen@gmail.com> writes:
> > We are running PG13.10 and recently we have encountered what appears to
> be
> > a bug due to some race condition between ALTER TABLE ... ADD CONSTRAINT
> and
> > some other catalog-writer, possibly ANALYZE.
> > The problem is that after successfully creating index on relation (which
> > previosly didnt have any indexes), its pg_class.relhasindex remains set
> to
> > "false", which is illegal, I think.
> > Index was built using the following statement:
> > ALTER TABLE "example" ADD constraint "example_pkey" PRIMARY KEY (id);
>
> ALTER TABLE ADD CONSTRAINT would certainly have taken
> AccessExclusiveLock on the "example" table, which should be sufficient
> to prevent anything else from touching its pg_class row.  The only
> mechanism I can think of that might bypass that is a manual UPDATE on
> pg_class, which would just manipulate the row as a row without concern
> for associated relation-level locks.  Any chance that somebody was
> doing something like that?
>
>                         regards, tom lane
>