Horton

Re: Postgres: Queries are too slow after upgrading to PG17 from PG15

Todd Cook <cookt@blackduck.com>

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From: Todd Cook <cookt@blackduck.com>
To: Merlin Moncure <mmoncure@gmail.com>
Cc: Peter Geoghegan <pg@bowt.ie>, Tom Lane <tgl@sss.pgh.pa.us>, Sajith Prabhakar Shetty <ssajith@blackduck.com>, Andrei Lepikhov <lepihov@gmail.com>, "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>
Date: 2025-09-25T18:07:11Z
Lists: pgsql-bugs

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Convert strategies to and from compare types

  2. Enhance nbtree ScalarArrayOp execution.

  3. Improve planning of btree index scans using ScalarArrayOpExpr quals.

  4. Fix planning of btree index scans using ScalarArrayOpExpr quals.

On 8/25/25, 8:30 AM, "Todd Cook" <cookt@blackduck.com <mailto:cookt@blackduck.com>> wrote:
> On 8/8/25, 6:04 PM, "Merlin Moncure" <mmoncure@gmail.com <mailto:mmoncure@gmail.com> <mailto:mmoncure@gmail.com > <mailto:mmoncure@gmail.com>>> wrote:
>> I think it is very likely going to address your issue, but
>> confirmation helps, and will make it more likely for this patch to be
>> pushed. After that, you will have to decide to downgrade to 15 or
>> suffer the status. quo until 18 releases. Running a custom patched 17
>> is possible if a patch could be made to appear, but I do not recommend
>> it given where you are at in the release calendar.
>
> We're still working on providing confirmation. Our load testing environment depends on
> third-party PG providers, so there's a significant amount of ongoing work to set up a
> configuration where we can use a custom PG build. This is a high priority for us, so it will
> get done, though maybe not for a couple more weeks yet.

We've finished the tests comparing PG18rc1 with and without the proposed patch,
including several runs each to verify reproducibility.  In short, the variance between the
two is well within what we normally see, so statistically speaking, the results are
indistinguishable.  However, the results are roughly on par with what we had been
seeing with PG 15 and 16, so maybe some other change from 17 to 18 eliminated the
regression we were seeing?

-- todd