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1M5QJJ-1vti6W2v93-001HRy for ; Mon, 23 Feb 2026 16:10:49 +0100 From: Attila Soki Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3864.400.21\)) Subject: Re: unstable query plan on pg 16,17,18 Date: Mon, 23 Feb 2026 16:10:38 +0100 References: To: pgsql-performance@postgresql.org In-Reply-To: Message-Id: <1695A676-062B-47C5-B302-91E2357DC874@gmx.net> X-Mailer: Apple Mail (2.3864.400.21) X-Provags-ID: V03:K1:5X5zBh+olc8ZYbV9LFI/bc8iOpIBGvkaYPO16ToTLw/Pn168sLy zgjgS027hIa5mbpD/8Y4pqMGldkUYtHff+MjPqEPj9KzsaH7xVhtGcB0bZONCK2GR+k6fIU LjJzXBVABEx93F8zwFDVntPSiahY+A+L32aIbyXZnpdtAXIM8GMTE464AaIeiJPpPrLAeHJ 4DZWSHQWIqbyZZvWvG5JQ== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:WseTC+rZizs=;SfWXmX9yQpHyTcammY4BiQ9awsI 1oPhIYaX3hCRjJOIRn36+7100dkjksl8cKWQlohJGO1mg9HsPmLQnzQxxgWb+m65lGMd6rCKQ Fm4UgsTh7gP8tUqb0YTvxUm8dFVrHWUaTmEpxIR4GT7IWbn/N1FecuEh1SqbwTJ6hj0qC4Il1 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OAkiDqRu4vfaKOAt3Bc8idiiD915elU+K3tG8ZxI9FWqQh82RmwhN7xiawCwkhbfiC+x7piWN h4lEk6O0gAzqhOvXS6hp0ZPoz8pWwG6qT75fTa8BJ8p/6Rd4knNKFg+ttHNuFACHDS756l9uT tMhMZrrrrLbvPsaeh6+dYOXcUF28cQlp1CwaplJRgkNl9H5KerLD/yFAE8PfESpKj07wkJl5F 1c6mdwZ3bgbs1r/V0ZSwggfpmqpPy5zlEwHQV9Cxx9egJdUDaA1NXw9HXu3O4Qd/Gs2ULRV0q Lmi+xd8IGmmnBYzvA= List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk > On 23 Feb 2026, at 10:41, Laurenz Albe = wrote: >=20 > On Mon, 2026-02-23 at 10:37 +0100, Attila Soki wrote: >> When upgrading from PostgreSQL 14.4, I noticed that one of my = somewhat complex >> analytical queries sometimes gets an inefficient plan under = PostgreSQL 16, 17, and 18. >> Under 14.4, the query runs with a stable plan and completes in 19 to = 22 seconds. >> In newer versions, the plan seems to be unstable, sometimes the query = completes >> in 17 to 20 seconds, sometimes it runs for 5 to 18 minutes with the = inefficient plan. >> This also happens even if the data is not significantly changed. >=20 > This is very likely owing to a bad estimate. >=20 > Could you turn on "track_io_timing" and send us the EXPLAIN (ANALYZE, = BUFFERS) output > for both the good and the bad plan? Hi Laurenz, Thank you for your reply. Here are the two explains. In order to be able to publish the plans here, I have obfuscated the = table and field names, but this is reversible, so I can provide more = info if needed. plan-ok: https://explain.depesz.com/s/hQvM plan-wrong: https://explain.depesz.com/s/uLvl Best regards, Attila