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Re: pg_plan_advice

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Ajay Pal <ajay.pal.k@gmail.com>
Cc: Jakub Wartak <jakub.wartak@enterprisedb.com>, Lukas Fittl <lukas@fittl.com>, Jacob Champion <jacob.champion@enterprisedb.com>, Dian Fay <di@nmfay.com>, Matheus Alcantara <matheusssilv97@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-01-26T16:07:55Z
Lists: pgsql-hackers

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Here is v12.

The big change in this version is that I've added extensive SGML
documentation for v0005. If the README was a little too low-level for
you, this might work better. If you'd like to view it without
downloading the patch set, I've put it up here:

https://robertmhaas.github.io/postgresql-static/html-pgpa-v12/pgplanadvice.html

Aside from that:

* Added a new GUC pg_plan_advice.always_store_advice_details. Without
that, you can't generate advice or see feedback on supplied advice
when using prepared queries, because we don't know at plan time that
it's right to incur the overhead of generating that stuff, and most of
the time it won't be.
* Revoked privileges on pg_clear_collected_shared_advice() as I had
already done on pg_get_collected_shared_advice().
* Removed a bogus elog(ERROR) in pgpa_walker_would_advise() in favor
of returning 0. I think somebody, likely Jakub, pointed this out
earlier, but I didn't quite absorb what I was being told until I
rediscovered the problem.
* Added a bunch more tests. I think the test coverage is getting
pretty decent now, but it could still use some tests targeting more
complex scenarios and corner cases. If you are curious about the
coverage report, see here:

https://robertmhaas.github.io/postgresql-static/coveragereport-pgpa-v12/contrib/pg_plan_advice/index.html

The low number for pgpa_scanner.l is basically bogus, but I don't know
of a way to make it not bogus. The low number for pgpa_ast.c is due to
a bunch of things related to bitmap scans not being right, which at
this point is, I think, the largest outstanding issue with the patch.
It's probably more interesting to look into ways of covering a few
more lines from pgpa_planner.c and pgpa_walker.c, which is where a lot
of the complexity in this code lives. Also, it would be nice to have
coverage of foreign scan cases, but I'm not quite sure what I need to
do to create tests for this module that also depend on postgres_fdw.
Any tips appreciated.

--
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.