Horton

Re: Statistics Import and Export

Corey Huinker <corey.huinker@gmail.com>

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From: Corey Huinker <corey.huinker@gmail.com>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, Michael Paquier <michael@paquier.xyz>, jian he <jian.universality@gmail.com>, Nathan Bossart <nathandbossart@gmail.com>, Bruce Momjian <bruce@momjian.us>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Magnus Hagander <magnus@hagander.net>, Stephen Frost <sfrost@snowman.net>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, alvherre@alvh.no-ip.org
Date: 2025-02-25T20:31:40Z
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. Change pg_dump default for statistics export.

  2. pg_dump: Adjust reltuples from 0 to -1 for dumps of older versions.

  3. vacuumdb: Don't skip empty relations in --missing-stats-only mode.

  4. pg_dump: Fix query for gathering attribute stats on older versions.

  5. Prevent redeclaration of typedef TocEntry.

  6. Remove unused function parameters in pg_backup_archiver.c.

  7. pg_dump: Retrieve attribute statistics in batches.

  8. pg_dump: Reduce memory usage of dumps with statistics.

  9. Skip second WriteToc() call for custom-format dumps without data.

  10. Add relallfrozen to pg_dump statistics.

  11. Matview statistics depend on matview data.

  12. Add pg_dump --with-{schema|data|statistics} options.

  13. Stats: use schemaname/relname instead of regclass.

  14. CREATE INDEX: do update index stats if autovacuum=off.

  15. Don't convert to and from floats in pg_dump.

  16. CREATE INDEX: don't update table stats if autovacuum=off.

  17. Organize and deduplicate statistics import tests.

  18. Address stats export review comments.

  19. Address stats import review comments.

  20. Add relallfrozen to pg_class

  21. Fix pg_strtof() to not crash on NULL endptr.

  22. Use attnum to identify index columns in pg_restore_attribute_stats().

  23. pg_dump: prepare attribute stats query.

  24. Avoid unnecessary relation stats query in pg_dump.

  25. Remove redundant pg_set_*_stats() variants.

  26. Do not use in-place updates for statistics import.

  27. Fix confusion about data type of pg_class.relpages and relallvisible.

  28. Documentation fixups for dumping statistics.

  29. Trial fix for old cross-version upgrades.

  30. Transfer statistics during pg_upgrade.

  31. Lock table in ShareUpdateExclusive when importing index stats.

  32. Use in-place updates for pg_restore_relation_stats().

  33. Improve error message for replication of generated columns.

  34. pg_dump: Add dumpSchema and dumpData derivative flags.

  35. Disallow modifying statistics on system columns.

  36. Add missing CommandCounterIncrement() in stats import functions.

  37. Add functions pg_restore_relation_stats(), pg_restore_attribute_stats().

  38. Documentation fixup.

  39. Add functions pg_set_attribute_stats() and pg_clear_attribute_stats().

  40. Change pg_*_relation_stats() functions to return type to void.

  41. Disable autovacuum for tables in stats import tests.

  42. Allow pg_set_relation_stats() to set relpages to -1.

  43. Fixup for pg_set_relation_stats().

  44. Create functions pg_set_relation_stats, pg_clear_relation_stats.

  45. Add memory/disk usage for Window aggregate nodes in EXPLAIN.

  46. Improve performance of dumpSequenceData().

  47. Add INJECTION_POINT_CACHED() to run injection points directly from cache

  48. Improve performance of binary_upgrade_set_pg_class_oids().

  49. Improve assertion in mdwritev()

  50. CREATE INDEX: do not update stats during binary upgrade.

  51. Redefine pg_class.reltuples to be -1 before the first VACUUM or ANALYZE.

On Tue, Feb 25, 2025 at 1:22 PM Jeff Davis <pgsql@j-davis.com> wrote:

> On Mon, 2025-02-24 at 12:50 -0500, Tom Lane wrote:
> > Also, while working on the attached, I couldn't help forming the
> > opinion that we'd be better off to nuke pg_set_attribute_stats()
> > from orbit and require people to use pg_restore_attribute_stats().
>
> Attached a patch to do so. The docs and tests required substantial
> rework, but I think it's for the better now that we aren't trying to do
> in-place updates.
>
> Regards,
>         Jeff Davis
>
>
All the C code changes make sense to me. Though as an aside, we're going to
run into the parameter-ordering problem when it comes to
pg_clear_attribute_stats, but that's a (read: my) problem for a later patch.

Documentation:

+         The currently-supported relation statistics are
+         <literal>relpages</literal> with a value of type
+         <type>integer</type>, <literal>reltuples</literal> with a value of
+         type <type>real</type>, and <literal>relallvisible</literal> with
a
+         value of type <type>integer</type>.

Could we make this a bullet-list? Same for the required attribute stats and
optional attribute stats. I think it would be more eye-catching and useful
to people skimming to recall the name of a parameter, which is probably
what most people will do after they've read it once to get the core
concepts.


Question:

Do we want to re-compact the oids we consumed in pg_proc.dat?


Test cases:

We're ripping out a lot of regression tests here. Some of them obviously
have no possible pg_restore_* analogs, such as explicitly set NULL values
vs omitting the param entirely, but some others may not, especially the
ones that test required arg-pairs.

Specifically missing are:

* regclass not found
* attribute is system column
* scalars can't have mcelem
* mcelem / mcelem freqs mismatch (parts 1 and 2)
* scalars can't have elem_count_histogram
* cannot set most_common_elems for range type

I'm less worried about all the tests of successful import calls, as the
pg_upgrade TAP tests kick those tires pretty well.

I'm also ok with losing the copies from test to test_clone, those are also
covered well by the TAP tests.

I'd feel better if we adapted the above tests from set-tests to
restore-tests, as the TAP suite doesn't really cover intentionally bad
stats.