| From: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | Sajith Prabhakar Shetty <ssajith(at)blackduck(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrei Lepikhov <lepihov(at)gmail(dot)com>, "pgsql-bugs(at)lists(dot)postgresql(dot)org" <pgsql-bugs(at)lists(dot)postgresql(dot)org>, Todd Cook <cookt(at)blackduck(dot)com> |
| Subject: | Re: Postgres: Queries are too slow after upgrading to PG17 from PG15 |
| Date: | 2025-08-21 02:58:41 |
| Message-ID: | CAHyXU0y1OK2XzzdgX5by9SML6fqpNtGcqRUPu4Hcjx1sjy82yg@mail.gmail.com |
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| Lists: | pgsql-bugs |
On Wed, Aug 20, 2025 at 7:48 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
>
> On Tue, Aug 12, 2025 at 12:46 AM Sajith Prabhakar Shetty
> <ssajith(at)blackduck(dot)com> wrote:
> > I can confirm with full certainty that both VACUUM and ANALYZE were executed on all three instances whose results I shared.
>
> The results that you shared showed "Heap Fetches: 598,916" -- one heap
> fetch per index search (for the problematic index scan).
>
> Perhaps VACUUM ran without being truly effective, due to the removable
> cutoff/horizon being held back by a long running query. Though that
> generally won't happen on a quiescent system -- so it really does look
> like VACUUM hasn't been run.
Try running VACUUM FREEZE. Do you have a way to frame up a dataset
for testing?
merlin
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