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Re: pg_plan_advice

Alexandra Wang <alexandra.wang.oss@gmail.com>

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From: Alexandra Wang <alexandra.wang.oss@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: "David G. Johnston" <david.g.johnston@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-03-12T23:45:49Z
Lists: pgsql-hackers 
Hi Robert,

On Thu, Mar 12, 2026 at 10:16 AM Robert Haas <robertmhaas@gmail.com> wrote:
> I'm still hoping to get some more feedback on the remaining patches,
> which are much smaller and conceptually simpler. While there is no
> time to redesign them at this point in the release cycle, there is
> still the opportunity to fix bugs, or decide that they're too
> half-baked to ship. So here is v20 with just those patches. Of course,
> post-commit review of the main patch is also very welcome.

Thanks for the patches!

I've run the meson tests for all three modules, and they all pass on
my laptop.

For the make tests, I had to add

+EXTRA_INSTALL = contrib/pg_plan_advice

in contrib/pg_collect_advice/Makefile in order for "make check" for
that module to run.

I don't really have a sense of how others feel about including these
modules, so I can't speak to that. Personally, though, I very much
like the test_plan_advice module because it gives me peace of mind,
and I feel it should accompany the already committed pg_plan_advice
module.

I reviewed the code and have a few minor comments:

0001:
The "make check" issue mentioned above.

0002:
Looks good to me.

0003:
There is a typo in the commit message:
"pg_stash.advice_stash" should be "pg_stash_advice.stash_name".

> stash->pgsa_stash_id = pgsa_state->next_stash_id++;

I doubt there will be more than 2 billion stashes in the system, but
if in any case we reach that number, we don't handle int overflow.
Should we set a limit on how many stashes can be stored?

Nit:
find_defelem_by_defname() is defined in all three modules, and also in
pg_plan_advice. Knowing it is very small, would it make sense to
extern the one in pg_plan_advice and reuse it?

Best,
Alex

-- 
Alexandra Wang
EDB: https://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.