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Re: pg_plan_advice

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Alexandra Wang <alexandra.wang.oss@gmail.com>
Cc: Richard Guo <guofenglinux@gmail.com>, Lukas Fittl <lukas@fittl.com>, Tom Lane <tgl@sss.pgh.pa.us>, 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: 2026-02-19T19:46:38Z
Lists: pgsql-hackers

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On Thu, Feb 19, 2026 at 1:53 AM Alexandra Wang
<alexandra.wang.oss@gmail.com> wrote:
> I'm about halfway through reviewing 0002 and only now finally
> understand what 0001 is doing. 0001 looks good to me.

Great!

> This took me a bit to work through. I'll send more feedback by the end
> of this week.

Yeah, it's a huge patch. Thanks for having a look through it. I look
forward to your feedback.

Here's v17. I have committed what was previously 0004 (which Richard
reviewed on another thread) so that is dropped from this version. In
addition, this version fixes the last issue that was causing failures
running test_plan_advice with pg_plan_advice.feedback_warnings=on. In
my previous email, I said that I thought the failure in question might
be caused by some undesirable coding in the self-join elimination
code, but that turned out to be incorrect. Instead, the problem was
that pga_identifier.c was using planenr_rt_fetch() in some places, and
it needs to use rt_fetch() everywhere. That's because
planner_rt_fetch() consults simple_rte_array, which both self-join
elimination and join removal can mutate, while rt_fetch() uses the
Query's rtable directly, and that never changes. Since we're trying to
create stable identifiers, "never changes" is what we want. In
addition to changing that, I also cleaned up a few XXX comments.

-- 
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.