Re: [BUGS] pg_dump(1) failures when concurrently refreshing mat views

Nico Williams <nico@cryptonector.com> writes:
> On Wed, Apr 19, 2017 at 05:20:31PM -0400, Tom Lane wrote:
>> ... uh, really?  It's not supposed to take anything higher than ACCESS
>> SHARE, which should coexist fine with anything short of ACCESS EXCLUSIVE.

> Whoops, sorry, that's a mistake in drafting the report.  You're right,
> it takes an ACCESS SHARE MODE lock, NOWAIT.  The remainder of the report
> remains correct.

But REFRESH CONCURRENTLY takes EXCLUSIVE lock, not ACCESS EXCLUSIVE lock,
so it won't conflict with pg_dump.  There's something missing from your
explanation.

Also, the only use of NOWAIT I see is in a parallel pg_dump worker.
It is known that parallel pg_dump can lead to deadlocks if third
parties are taking ACCESS EXCLUSIVE locks --- but you haven't identified
where the ACCESS EXCLUSIVE request is coming from.
        regards, tom lane


-- 
Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-bugs