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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: 2026-01-12T17:13:32Z
Lists: pgsql-hackers

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On Sun, Jan 11, 2026 at 3:21 PM Lukas Fittl <lukas@fittl.com> wrote:
> I wonder a bit if we shouldn't instead focus on this being about the
> inputs to create_append_path (and the 4 different variants of calling
> it in add_paths_to_append_rel), and make sure we group some of them
> together in a struct, but still pass the individual fields of that
> struct to accumulate_append_subpaths.
>
> I've sketched out what I mean in the attached

This is a good idea, IMHO. It didn't compile and I made some other
cosmetic fixes, but I like the direction.

Here's v9. Changes:

* Updated all patches with reviewers to date and discussion link. I
have listed the same reviewers for all of 0001-0004, but the list for
0005 is different, based on my reading of the emails on this thread.
If someone feels that I've made the wrong choices about listing them,
please let me know.
* Incorporated Lukas's idea into 0003 and listed him as a co-author.
* Some comment improvements to 0004.

In 0005:

* Disallow JOIN_ORDER() without targets, per feedback from Ajay Pal.
* pgindent
* Incorporate the fix to pgpa_process_unrolled_join() that I
previously posted separately, and update the associated comments.

I now feel that I've had enough substantial feedback on 0003 and 0004
that it wouldn't be crazy to think about committing those, unless
further review turns up problems or something. I think I need more
substantial review on 0001 and 0002 before I could consider moving
forward with those. And 0005 needs a lot more review, and also a lot
more work from my side. Given that, where do I go from here? I don't
think it makes sense to commit 0002 or 0003 without 0001, but 0004 is
mostly independent of 0001-0003. So, I think that if more feedback on
0001 and 0002 is forthcoming soon, I'll probably just wait a bit and
hope to commit 0001-0004 in the current order. If not, I'll rearrange
the series to move 0004 to the front, and plan to commit that first.

-- 
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.