Horton

Extended Statistics set/restore/clear functions.

Corey Huinker <corey.huinker@gmail.com>

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From: Corey Huinker <corey.huinker@gmail.com>
To: pgsql-hackers@lists.postgresql.org
Date: 2025-01-22T18:17:27Z
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

This is a separate thread for work started in [1] but focused purely on
getting the following functions working:

* pg_set_extended_stats
* pg_clear_extended_stats
* pg_restore_extended_stats

These functions are analogous to their relation/attribute counterparts, use
the same calling conventions, and build upon the same basic infrastructure.

I think it is important that we get these implemented because they close
the gap that was left in terms of the ability to modify existing statistics
and to round out the work being done to carry over statistics via
dump/restore and pg_upgrade i [1].

The purpose of each patch is as follows (adapted from previous thread):

0001 - This makes the input function for pg_ndistinct functional.

0002 - This makes the input function for pg_dependencies functional.

0003 - Makes several static functions in attribute_stats.c public for use
by extended stats. One of those is get_stat_attr_type(), which in the last
patchset was modified to take an attribute name rather than attnum, thus
saving a syscache lookup. However, extended stats identifies attributes by
attnum not name, so that optimization had to be set aside, at least
temporarily.

0004 - These implement the functions pg_set_extended_stats(),
pg_clear_extended_stats(), and pg_restore_extended_stats() and behave like
their relation/attribute equivalents. If we can get these committed and
used by pg_dump, then we don't have to debate how to handle post-upgrade
steps for users who happen to have extended stats vs the approximately
99.75% of users who do not have extended stats.

This patchset does not presently include any work to integrate these
functions into pg_dump, but may do so once that work is settled, or it may
become its own thread.

[1]
https://www.postgresql.org/message-id/CADkLM=c6NHdXU+d+m1yASZ4NT_qye1LCnaU2Vgf8YJ80jJT-Qg@mail.gmail.com