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Re: pg_plan_advice

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Andrei Lepikhov <lepihov@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Alexander Lakhin <exclusion@gmail.com>, Lukas Fittl <lukas@fittl.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-04-06T13:56:23Z
Lists: pgsql-hackers 
Hi,

On 2026-04-04 23:02:37 +0200, Andrei Lepikhov wrote:
> On 4/4/26 20:42, Robert Haas wrote:
> > On Sat, Apr 4, 2026 at 5:34 AM Andrei Lepikhov <lepihov@gmail.com> wrote:
> > By the way, I'm really glad you hit that error. That particular error
> > check is there precisely to find plans that pg_plan_advice isn't able
> > to understand, and it sounds like it is doing its job as intended.
> > Having problems isn't great, but knowing that you have problems is a
> > lot better than still having them but not knowing about it.
> That’s exactly what concerns me. I see it as a potential design flaw if the
> extension has to make assumptions about possible plan configurations.
> I’m not sure how it works in detail, of course. However, when I designed
> Postgres replanning in the past, and made similar core changes to what
> you’ve done for pg_plan_advice, this kind of problem couldn’t have happened.
> So, I think it’s worth questioning the current approach and looking for
> other options.

You're making sweeping high-level demands, implying they're easy ("when I
designed ... this kind of problem couldn’t have happened"), without any
concrete technical suggestions for how to actually achieve that.  In very
strong language.  Your high level demand, that somehow plan shape influencing
code should just work regardless of what crazy thing extensions have done
seems ... not entirely realistic, to put it very kindly.

I suggest you rethink your approach of engaging with others.

Greetings,

Andres Freund

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.