Horton

Re: BUG #14941: Vacuum crashes

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Andres Freund <andres@anarazel.de>
Cc: "Bossart, Nathan" <bossartn@amazon.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Lyes Ameddah <lyes.amd@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, "pgsql-bugs@postgresql.org" <pgsql-bugs@postgresql.org>
Date: 2018-04-03T05:11:46Z
Lists: pgsql-bugs, pgsql-hackers 
On Fri, Mar 30, 2018 at 05:19:46PM -0700, Andres Freund wrote:
> On 2018-03-30 18:39:01 +0000, Bossart, Nathan wrote:
>> I think the most straightforward approach for fixing this is to add
>> skip-locked functionality in find_all_inheritors(),
>> find_inheritance_children(), and vac_open_indexes(), but I am curious
>> what others think.

For vac_open_indexes() it may make the most sense to introduce a new
try_open_index which wraps on top of try_relation_open with checks on
the opened relation's relkind. 

> I'm actually wondering if we shouldn't just ignore this problem. While
> the other cases VACUUM (SKIP LOCKED) are intended to solve seem common,
> these seem less so. But it'd be a bit weird, too..

Wouldn't that cause deadlocks if one session has VACUUM (SKIP_LOCKED)
and another session running vacuum or autovacuum if simply ignored?
That looks dangerous to me than simply skipping a lock that cannot be
taken.
--
Michael

Commits

  1. Add option SKIP_LOCKED to VACUUM and ANALYZE

  2. Rename VACOPT_NOWAIT to VACOPT_SKIP_LOCKED

  3. Add parenthesized options syntax for ANALYZE.

  4. Don't allow VACUUM VERBOSE ANALYZE VERBOSE.

  5. Fix inadequate locking during get_rel_oids().

  6. Avoid having autovacuum workers wait for relation locks.