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Re: pg_plan_advice

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Lukas Fittl <lukas@fittl.com>
Cc: Jacob Champion <jacob.champion@enterprisedb.com>, Dian Fay <di@nmfay.com>, Matheus Alcantara <matheusssilv97@gmail.com>, Jakub Wartak <jakub.wartak@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-01-08T19:23:48Z
Lists: pgsql-hackers 
On Thu, Jan 8, 2026 at 2:14 PM Lukas Fittl <lukas@fittl.com> wrote:
> On Thu, Jan 8, 2026 at 10:22 AM Robert Haas <robertmhaas@gmail.com> wrote:
> > 0004: Comment update, bug fix to cost_index() per comment from Lukas.
>
> Thanks! I've tested this and this works as expected on current master
> with the updated pg_hint_plan code, and checking for tablesample in
> the code that sets the mask.

Nice!

> > How about checking rte->tablesample, as set_rel_pathlist does?
>
> Yeah, that works - its a bit inconvenient for two reasons, but I don't
> think that warrants a redesign:
>
> 1) get_relation_info_hook doesn't get a RangeTblEntry passed (like
> set_rel_pathlist_hook), but that's solvable by looking it up via
> simple_rte_array

That's a pretty normal thing to have to do in this kind of code, IMHO.

> 2) It requires maintaining a special case in the logic that says "make
> it parallel", vs the planner that is authoritative (i.e. if we add
> more special cases in the future, each extension will have to be
> updated to reflect that)

IMHO, this is a policy decision by the extension and so the logic
belongs in the extension. pg_plan_advice has no similar exception,
because it made a different policy decision.

Overall, I feel that your experiment here is a pretty compelling
argument for committing 0004 (the pgs_mask stuff). I'm not sure it's
quite time to do that yet, because maybe there are still some design
changes we want to consider for it, or maybe somebody else wants to
review first. But even if that patch did nothing other than get rid of
lots of complexity and copy-paste in pg_hint_plan, that would be
enough to justify this infrastructure. The fact that basically works
as intended for both pg_plan_advice and pg_hint_plan, despite them
having no common code, is a really good sign, IMHO.

-- 
Robert Haas
EDB: http://www.enterprisedb.com

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.