From: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
---|---|
To: | tlw(at)monsido(dot)com |
Cc: | PostgreSQL Bugs <pgsql-bugs(at)postgresql(dot)org> |
Subject: | Re: BUG #14960: Queries stuck on BtreePage lock on parallel index scan |
Date: | 2017-12-11 09:42:14 |
Message-ID: | CAEepm=0M6M65tLDShTCf1qynzV2wMfU1T7oq4GH1q0wku19-_w@mail.gmail.com |
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Lists: | pgsql-bugs |
On Mon, Dec 11, 2017 at 10:22 PM, <tlw(at)monsido(dot)com> wrote:
> The following bug has been logged on the website:
>
> Bug reference: 14960
> Logged by: Tim Warberg
> Email address: tlw(at)monsido(dot)com
> PostgreSQL version: 10.1
> Operating system: Ubuntu 16.04 LTS
> Description:
>
> Hi,
>
> Ran into a issue on our PostgreSQL 10.1 cluster that seems to be a parallel
> index scan bug. Our queue system scheduled 30 almost identical concurrent
> queries where some of them was executed as parallel queries and all of them
> became stuck on IPC BtreePage lock.
Hi Tim,
Thanks for the report. This seems to be the same as the bug that we
just analysed over here:
> We discovered this after they've been
> stuck like that for about 10 hours [1]. At the same time a autovacuum was
> progressing one of the queried tables and it had become stuck in LWLock
> buffer_content while vacuuming indexes. None of the query processes
> responded to pg_cancel_backend nor pg_terminate_backend including the
> autovacuum.
Hmm. This may be because we hold a BT_READ lock while waiting in
_bt_parallel_seize(). Here it's extended by the above-mentioned bug,
preventing others from acquiring an exclusive lock.
--
Thomas Munro
http://www.enterprisedb.com
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