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Re: pg_plan_advice

Alexander Lakhin <exclusion@gmail.com>

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From: Alexander Lakhin <exclusion@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>, Lukas Fittl <lukas@fittl.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-03-27T06:00:00Z
Lists: pgsql-hackers 
Hello Robert.

27.03.2026 01:25, Robert Haas wrote:
> Thanks. Committed. Nothing has obviously broken so far, BUT even
> machines like skink that were failing weren't failing on every run, so
> it may be a while before we get a clear view of the situation --
> unless of course this didn't fix it or even made things worse, in
> which case we might find out a lot faster. Hopefully not, but then I
> thought this was going to work the first time.

I could not reproduce recent failures from skink and morepork so far, but
I found that changing some GUCs can trigger similar warnings, e.g.:
echo "join_collapse_limit = 1000" >/tmp/extra.config
TEMP_CONFIG=/tmp/extra.config make -s check -C src/test/modules/test_plan_advice/
--- .../src/test/regress/expected/identity.out       2026-02-13 06:15:55.871368851 +0200
+++ .../src/test/modules/test_plan_advice/tmp_check/results/identity.out 2026-03-27 06:50:11.123234266 +0200
@@ -10,6 +10,8 @@
  ALTER TABLE itest3 ALTER COLUMN a ADD GENERATED ALWAYS AS IDENTITY;  -- error
  ERROR:  column "a" of relation "itest3" is already an identity column
  SELECT table_name, column_name, column_default, is_nullable, is_identity, identity_generation, identity_start, 
identity_increment, identity_maximum, identity_minimum, identity_cycle FROM information_schema.columns WHERE table_name 
LIKE 'itest_' ORDER BY 1, 2;
+WARNING:  supplied plan advice was not enforced
+DETAIL:  advice JOIN_ORDER(nc (co nco (c a)) t (bt nbt) ad nt (dep seq)) feedback is "matched, failed"
...

echo "geqo_threshold = 8" >/tmp/extra.config
TEMP_CONFIG=/tmp/extra.config make -s check -C src/test/modules/test_plan_advice/
--- .../src/test/regress/expected/create_function_sql.out 2026-02-13 06:15:55.865368936 +0200
+++ .../src/test/modules/test_plan_advice/tmp_check/results/create_function_sql.out 2026-03-27 06:53:44.235504942 +0200
@@ -482,6 +482,9 @@
      FROM information_schema.parameters JOIN information_schema.routines USING (specific_schema, specific_name)
      WHERE routine_schema = 'temp_func_test' AND routine_name ~ '^functest_is_'
      ORDER BY 1, 2;
+WARNING:  supplied plan advice was not enforced
+DETAIL:  advice JOIN_ORDER(n (ss (p (t#2 nt#2) l)) t nt) feedback is "matched, failed"
+advice NESTED_LOOP_PLAIN((ss p l t#2 nt#2)) feedback is "matched, failed"
   routine_name  | ordinal_position | parameter_name | parameter_default
...

and an assertion failure with:
enable_parallel_append = off
enable_partitionwise_aggregate = on
cpu_tuple_cost = 1000

TRAP: failed Assert("relids != NULL"), File: "pgpa_scan.c", Line: 248, PID: 1956762
...
2026-03-27 07:51:02.562 EET postmaster[1956525] LOG:  client backend (PID 1956762) was terminated by signal 6: Aborted
2026-03-27 07:51:02.562 EET postmaster[1956525] DETAIL:  Failed process was running: SELECT COUNT(*) FROM 
stats_import.part_parent;

Best regards,
Alexander

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.