Re: Significant performance issues with array_agg() + HashAggregate plans on Postgres 17

From: David Rowley <dgrowleyml(at)gmail(dot)com>
To: Scott Carey <scott(dot)carey(at)algonomy(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-performance(at)lists(dot)postgresql(dot)org
Subject: Re: Significant performance issues with array_agg() + HashAggregate plans on Postgres 17
Date: 2026-04-01 11:12:18
Message-ID: CAApHDvoQUwsuvdhrxVOLsMYWcXZPAMvWweyemCg-q0=dmF3h2w@mail.gmail.com
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On Wed, 1 Apr 2026 at 20:18, Scott Carey <scott(dot)carey(at)algonomy(dot)com> wrote:
> The run times are consistent enough (within a 15% range most of the time on the busy server), yet we are talking about a 50x performance difference, dwarfing the time variation.

If you're able to install the debug symbols and run perf top or perf
record and send us the perf report for one of the problem machines,
that might yield something interesting.

David

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