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Re: pg_plan_advice

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Lukas Fittl <lukas@fittl.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, 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: 2026-01-29T06:44:24Z
Lists: pgsql-hackers 
> On Wed, Jan 28, 2026 at 6:41 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > skink's not happy:
> >
> > =2162940== VALGRINDERROR-BEGIN
> > ==2162940== Conditional jump or move depends on uninitialised value(s)
> > ==2162940==    at 0x434D366: cost_material (costsize.c:2593)
> > ==2162940==    by 0x436E7E9: materialize_finished_plan (createplan.c:6531)
> > ==2162940==    by 0x4383054: standard_planner (planner.c:533)
> > ...
> > ==2162940==    by 0x44CD09D: ProcessUtility (utility.c:525)
> > ==2162940==  Uninitialised value was created by a stack allocation
> > ==2162940==    at 0x436E76A: materialize_finished_plan (createplan.c:6506)

FWIW, the following related code in reparameterize_path() seems unsafe
to me:

    spath = reparameterize_path(root, spath,
                                required_outer,
                                loop_count);
    enabled =
        (mpath->path.disabled_nodes <= spath->disabled_nodes);
    if (spath == NULL)
        return NULL;
    return (Path *) create_material_path(rel, spath, enabled);

I think we should access spath->disabled_nodes until after we have
verified that spath is not NULL.

Also, it's not quite clear to me why create_material_path (and
cost_material) requires the "enabled" parameter.  I couldn't find any
comments on this, so it might be worth adding some comments here.

- Richard

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.