Horton

Re: Extended Statistics set/restore/clear functions.

Corey Huinker <corey.huinker@gmail.com>

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From: Corey Huinker <corey.huinker@gmail.com>
To: Tomas Vondra <tomas@vondra.me>
Cc: Michael Paquier <michael@paquier.xyz>, jian he <jian.universality@gmail.com>, pgsql-hackers@lists.postgresql.org, tgl@sss.pgh.pa.us
Date: 2025-11-05T06:38:56Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add test doing some cloning of extended statistics data

  2. Add test for pg_restore_extended_stats() with multiranges

  3. Add support for "mcv" in pg_restore_extended_stats()

  4. Include extended statistics data in pg_dump

  5. Add support for "dependencies" in pg_restore_extended_stats()

  6. Add test for MAINTAIN permission with pg_restore_extended_stats()

  7. Add pg_restore_extended_stats()

  8. Add routine to free MCVList

  9. Improve pg_clear_extended_stats() with incorrect relation/stats combination

  10. Add pg_clear_extended_stats()

  11. Introduce routines to validate and free MVNDistinct and MVDependencies

  12. Fix typo in stat_utils.c

  13. Move attribute statistics functions to stat_utils.c

  14. Improve error messages of input functions for pg_dependencies and pg_ndistinct

  15. Improve test output of extended statistics for ndistinct and dependencies

  16. Fix some compiler warnings

  17. Add input function for data type pg_dependencies

  18. Add input function for data type pg_ndistinct

  19. Rework output format of pg_dependencies

  20. Rework output format of pg_ndistinct

  21. Fix comments of output routines for pg_ndistinct and pg_dependencies

  22. Move code specific to pg_dependencies to new file

  23. Move code specific to pg_ndistinct to new file

  24. Document some structures in attribute_stats.c

  25. Fix FATAL message for invalid recovery timeline at beginning of recovery

Attachments

>
> Otherwise users may not benefit from this pg_upgrade feature for a
> couple more years. Plenty of users delay upgrading until the EOL gets
> close, and so might be unable to dump/restore extended stats for the
> next ~5 years


Paquier's response got sidetracked because of an errant subject line
change, so I will try to recap:

* pg_dump code changes no longer seem as bad on second look
* proceed with breakout per off-list discussion

in that off-list discussion I proposed (though I was mostly echoing what I
thought Paquier wanted):

1. pg_ndistinct output function change.
2. pg_ndistinct input function addition.
3. pg_dependencies output function change
4. pg_dependencies input function
5. Expose attribute statistics function and rename them attstat_* or
statatt_*   (edit: and fix lack of comments on the enums and arrays)
6. pg_restore_extended_stats
7. pg_dump with no ability to fetch old-format pg_ndistinct/pg_dependences.
(edit: and fix inherited bug)
8. pg_dump working back as far as possible

Given that the pg_dump code no longer seems as bad, and Tomas is very much
in support of it, I've opted not to split out steps 7/8.