From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Geoghegan <pg@bowt.ie>
cc: Shijia Wei <shijiawei@utexas.edu>,
 Laurenz Albe <laurenz.albe@cybertec.at>,
        pgsql-performance@lists.postgresql.org
Subject: Re: Consecutive Query Executions with Increasing Execution Time
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Comments: In-reply-to Peter Geoghegan <pg@bowt.ie>
	message dated "Mon, 16 Dec 2019 12:39:10 -0800"
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Date: Mon, 16 Dec 2019 15:50:17 -0500
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Peter Geoghegan <pg@bowt.ie> writes:
> Why do the first and the twentieth executions of the query have almost
> identical "buffers shared/read" numbers? That seems odd.

It's repeat execution of the same query, so that doesn't seem odd to me.

This last set of numbers suggests that there's some issue with the
parallel execution infrastructure in particular, though I don't see what
it would be.  Doesn't execParallel wait for the workers to exit before
the leader finishes its query?  If so, how is there any persistent state
that would interfere with a later query?

			regards, tom lane