Horton
Menu

Re: pg_plan_advice

Robert Haas <robertmhaas@gmail.com>

View thread
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: 2026-02-27T22:46:21Z
Lists: pgsql-hackers

Attachments

On Thu, Feb 26, 2026 at 8:55 AM Robert Haas <robertmhaas@gmail.com> wrote:
> Thanks, Alex, for the review.

Here's v18. In addition to fixing the problems pointed out by Alex,
there are a couple of significant changes in this version.

First, I realized that it might be confusing to have the collector
interface as part of pg_plan_advice, because for most of what
pg_plan_advice does, you didn't need the extension, but for that part,
you did. So, I broke that part out into its own extension, now called
pg_collect_advice, and put it into a separate patch. I think this is
conceptually cleaner: pg_plan_advice is just the core functionality of
generating and enforcing advice, and anything else is a separate
extension that logically sits on top of that core functionality. This
also has the advantage that you can decide to make the core
functionality available without any chance of somebody getting access
to the collector, if desired.

Second, I also added a third contrib module called pg_stash_advice.
This uses the same hook that I previously added for test_plan_advice,
but unlike that module, this one's not just a test. It lets you set up
an "advice stash" which is basically a query_id->advice_string hash
table. If you then set pg_stash_advice.stash_name to the name of your
advice stash, it will do a lookup into that hash table every time a
query is planned and, if the query ID is found, it will do the
planning with the corresponding advice string. What I think is
particularly cool about this is that it shows that you can really use
that hook to apply advice on the fly in any way you want. I suspect
that query ID matching will be suitable for a lot of use cases, but
you could have a similar module that matches on query text or does
anything else that you want as long as an advice string pops out at
the end. It shows that the core pg_plan_advice infrastructure is
pluggable. So this is both something that I think a lot of people will
find useful all on its own, and also a design pattern that people can
copy and adapt.

Finally, I did a lot of minor cleanups. I originally planned to try to
include a full list in this email, but as the number of fixes got
larger, I eventually realized that would get incredibly tedious, even
for me. An awful lot of what got fixed was just straightforward typos,
but there were also some comments where the wording was garbled and
didn't really make sense, or where I thought the comment should be
longer or shorter than it actually was, or where I used the wrong data
type in the code but in a way that didn't actually break anything.
There are a few fixes to the code, but they're all very minor stuff
that I'm not sure has any real-world consequences, although it might
so it's good to fix it, but the overwhelming bulk of it is cosmetic.

Thanks,

-- 
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.