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Re: pg_plan_advice

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Alexander Lakhin <exclusion@gmail.com>, Lukas Fittl <lukas@fittl.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-04-03T18:20:32Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> (In fact, I had a little bit of trouble finding this in the BF results
> even knowing it was there: filtering by test_plan_advice failures
> doesn't find anything recent. sifaka's failure shows up as
> TestModulesCheck-en_US.UTF-8, but frustratingly, the names for the
> stage logs don't seem to quite match the name of what failed. There is
> testmodules-install-check-C and
> testmodules-install-check-en_US.UTF-8, but those have "install" in the
> name and are punctuated differently, so it's not instantly clear that
> it's the same thing. Anyway, I do see it in there now, but what I'm
> saying is that if there have been other failures that are related to
> this, it's possible I have missed them due to stuff like this, so it's
> helpful that you (Tom) pointed this one out.)

I grepped the buildfarm database for 'supplied plan advice' and got
no other hits since 6455e55b0 went in.  That's not a huge sample
size of course, but probably several hundred runs so far.  If there's
another message wording I should check for, let me know.

> Tom, would welcome your thoughts, if you have any, and anyone else's
> thoughts as well. If none, I'll proceed as described above and update
> when I know more.

I don't like anything in category 1 except (1a) run the test scripts
serially for test_plan_advice.  As I said before, I am strongly
against allowing test_plan_advice to constrain what our tests do.

Another idea in category 2, which I think is a bit different from
any option you listed, is to repeat the "plan without advice, then
again with advice, see if it matches" process up to maybe 5-ish times
before declaring failure.  If it works any one time, then write off
the previous failures as being induced by concurrent activity.
Unlike what you mentioned, this isn't dependent on sinval checks,
which I think are next door to useless in the context of the
regression tests: there's a constant storm of sinval activity going
on, to the point where you might as well figure "check for sinval
arrival" is constant "true".

However, eyeing the calendar, I think the only options that are likely
to be stabilizable before feature freeze are (1a) run the test scripts
serially for test_plan_advice or (3a) throw test_plan_advice away.
I know you don't want to do (3a) and I understand why not.  How much
will (1a) slow things down?

			regards, tom lane

Commits

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

  1. pg_plan_advice: Fix another unique-semijoin bug.

  2. pg_plan_advice: Export feedback-related definitions.

  3. pg_plan_advice: Fix a bug when a subquery is pruned away entirely.

  4. pg_plan_advice: Add alternatives test to Makefile.

  5. pg_plan_advice: Handle non-repeatable TABLESAMPLE scans.

  6. pg_stash_advice: Allow stashed advice to be persisted to disk.

  7. Add pg_stash_advice contrib module.

  8. pg_plan_advice: Avoid assertion failure with partitionwise aggregate.

  9. pg_plan_advice: Invent DO_NOT_SCAN(relation_identifier).

  10. Add an alternative_plan_name field to PlannerInfo.

  11. pg_plan_advice: Refactor to invent pgpa_planner_info

  12. Respect disabled_nodes in fix_alternative_subplan.

  13. get_memoize_path: Don't exit quickly when PGS_NESTLOOP_PLAIN is unset.

  14. test_plan_advice: Set TAP test priority 50 in meson.build.

  15. pg_plan_advice: Avoid a crash under GEQO.

  16. Test pg_plan_advice using a new test_plan_advice module.

  17. pg_plan_advice: Always install pg_plan_advice.h, and in the right place

  18. pg_plan_advice: Fix failures to accept identifier keywords.

  19. Add pg_plan_advice contrib module.

  20. Allow extensions to mark an individual index as disabled.

  21. Replace get_relation_info_hook with build_simple_rel_hook.

  22. Store information about Append node consolidation in the final plan.

  23. Store information about elided nodes in the final plan.

  24. Store information about range-table flattening in the final plan.

  25. Pass cursorOptions to planner_setup_hook.

  26. Fix PGS_CONSIDER_NONPARTIAL interaction with Materialize nodes.

  27. Fix mistakes in commit 4020b370f214315b8c10430301898ac21658143f

  28. Allow for plugin control over path generation strategies.

  29. Update some comments for fasthash

  30. Allow passing a pointer to GetNamedDSMSegment()'s init callback.

  31. Don't reset the pathlist of partitioned joinrels.

  32. Treat number of disabled nodes in a path as a separate cost metric.