| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Sajith Prabhakar Shetty <ssajith(at)blackduck(dot)com> |
| Cc: | Andrei Lepikhov <lepihov(at)gmail(dot)com>, "pgsql-bugs(at)lists(dot)postgresql(dot)org" <pgsql-bugs(at)lists(dot)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: Postgres: Queries are too slow after upgrading to PG17 from PG15 |
| Date: | 2025-07-30 18:45:39 |
| Message-ID: | CAH2-WzknRnYgiaOtOg9XyPec6FmA5PkbwneU5HsdGhxKmutRmg@mail.gmail.com |
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| Lists: | pgsql-bugs |
On Mon, Jul 28, 2025 at 4:41 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> The query takes ~1550ms on my local workstation. If I just comment out
> the relevant qsort, it'll take only ~190 ms. That qsort might not be
> the only problem here, but it is the immediate problem. Note that
> commenting out the qsort should produce the same answer, at least for
> this one query, since the constants that appear in the query are
> already sorted (the EXPLAIN row counts match what they show with the
> qsort in place).
Actually, that isn't quite true -- the constants weren't in sorted order.
I find that if I presort the elements within the query text itself,
the runtime goes down to only ~410ms. That's still not great, but it
is a vast improvement.
--
Peter Geoghegan
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