From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Steve Kehlet <steve(dot)kehlet(at)gmail(dot)com> |
Cc: | Forums postgresql <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: how to investigate GIN fast updates and cleanup cycles? |
Date: | 2015-08-28 17:11:41 |
Message-ID: | 25246.1440781901@sss.pgh.pa.us |
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Lists: | pgsql-general |
Steve Kehlet <steve(dot)kehlet(at)gmail(dot)com> writes:
> This is Postgres 9.4.4. I am troubleshooting some occasional (every 3-4
> hours) slowness with UPDATEs on a table that has a GIN index on a JSONB
> column. During these episodes, UPDATEs that normally take < 1sec take
> upwards of 2-4 minutes, and all finish simultaneously, like they were all
> blocked on something and finally got released.
Hm ... have you tried checking pg_locks to see if they're blocked on
something identifiable?
You might be right that this is caused by flushing the GIN pending list,
but I thought that that was not supposed to block concurrent insertions.
What I'd expect to see is *one* insert taking significantly longer than
normal, but no effect on concurrent operations. Also, 2-4 minutes sounds
much longer than should be needed to flush a 10MB pending list, anyway.
regards, tom lane
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