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Re: pg_plan_advice

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Jacob Champion <jacob.champion@enterprisedb.com>
Cc: Dian Fay <di@nmfay.com>, Matheus Alcantara <matheusssilv97@gmail.com>, Jakub Wartak <jakub.wartak@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-01-08T18:21:35Z
Lists: pgsql-hackers

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On Wed, Jan 7, 2026 at 6:11 PM Jacob Champion
<jacob.champion@enterprisedb.com> wrote:
> On Mon, Dec 15, 2025 at 12:06 PM Robert Haas <robertmhaas@gmail.com> wrote:
> > - Add gather((d d/d.d)) test case, per Jacob, and fix the related bug
> > in pgpa_identifier_matches_target, per Jacob's email.
>
> I think this fix affected the ability to omit the partition schema in
> advice strings. Attached is a quick test that shows it on my machine,
> plus an attempted fix that mashes together the v6 and v7 approaches.
> (I have diffs in my generated plan advice compared to what's in
> v7-0005, so I'm not sure if my .out file is correct.)

Right, so I also am seeing some instability in the plans for some of
the test cases. I've attempted to address that in v8 by making the
three partitioned tables have unequal row counts. I also adapted your
test case and adopted your code fix. Unfortunately, I haven't been
able to respond to everyone's reports about v7 yet, partly because of
Christmas vacation, partly because of the number of reports, and
partly because, uh, I'm slow I guess. But here's the list of things
that have changed:

0001, 0003: No changes.

0002: Comment update.

0004: Comment update, bug fix to cost_index() per comment from Lukas.

- Added an XXX to the README to highlight the need for more GEQO investigation.
- Regression test expected output changes.
- Make partitionwise_join test tables different sizes in the hopes of
stabilizing test results.
- Add test case for forcing partitionwise join order with and without
a schema specification.
- Add new GUC pg_plan_advice.trace_mask because I've written similar
debugging code too many times already.
- Replace reference to inner_beneath_any_gather[i] with
inner_beneath_any_gather[k] per comment from Jakub.
- Add logic to pgpa_planner_apply_join_path_advice taking into account
that PARTITIONWISE() implicitly constrains the join order.
- Rebased.

-- 
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.