On Fri, Aug 28, 2015 at 10:11 AM Tom Lane <t...@sss.pgh.pa.us> wrote:
> Steve Kehlet <steve.keh...@gmail.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? > Yes, I should have mentioned that, I have a cronjob going every minute dumping out [blocked/blocking queries]( https://gist.github.com/skehlet/fbf5f52e18149e14e520) and nothing has shown up related to these queries (there were some other normal unrelated results, so I believe the job+query itself are working). After several incidents I believe it would have logged something. > 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. Yeah head scratch. That is really weird. Still gathering data, any way I can see for sure when these cleanup cycles are occurring?
