Re: how to investigate GIN fast updates and cleanup cycles?

Steve Kehlet <steve.kehlet@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?

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