Horton

Re: Extended Statistics set/restore/clear functions.

Corey Huinker <corey.huinker@gmail.com>

View thread
From: Corey Huinker <corey.huinker@gmail.com>
To: jian he <jian.universality@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, Tomas Vondra <tomas@vondra.me>, pgsql-hackers@lists.postgresql.org, tgl@sss.pgh.pa.us
Date: 2025-11-12T22:21:36Z
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

>
> +
> + appendStringInfo(&str, "], \"" PG_NDISTINCT_KEY_NDISTINCT "\": %d}",
> + (int) item.ndistinct);
>
> I’m a bit confused about the part above,
> item.ndistinct is double type, we just cast it to int type?
>

It's a historical quirk. That's what the original output function did in
mvdistinct.c, so we maintain compatibility with that. Altering the internal
storage type would affect the bytea serialization, which would break binary
compatibility.


> after apply 0004, the below in doc/src/sgml/perform.sgml also need to
> change?
>

Yes it does, good catch.


> Do you think it's worth the trouble to have two separate
> appendStringInfoChar for ``{}``?
>
> for example in loop ``for (i = 0; i < ndist->nitems; i++)``. we can change
> to:
>

I agree that that feels more symmetrical. However, it seems the prevailing
wisdom is that we're already paying for a string interpolation in the very
next appendStringInfo(), we might as well save ourselves a function call.
Hence, I left that one as-is.

The sgml change has been worked into a rebased and reduced patch set
(thanks for the commits Michael!)