Horton

Re: Statistics Import and Export

Corey Huinker <corey.huinker@gmail.com>

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From: Corey Huinker <corey.huinker@gmail.com>
To: jian he <jian.universality@gmail.com>
Cc: Jeff Davis <pgsql@j-davis.com>, Nathan Bossart <nathandbossart@gmail.com>, Bruce Momjian <bruce@momjian.us>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, 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: 2025-02-06T04:01:13Z
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.

Attachments

On Mon, Jan 27, 2025 at 11:09 AM Corey Huinker <corey.huinker@gmail.com>
wrote:

> On Mon, Jan 27, 2025 at 9:05 AM jian he <jian.universality@gmail.com>
> wrote:
>
>> On Tue, Jan 21, 2025 at 7:31 AM Jeff Davis <pgsql@j-davis.com> wrote:
>> >
>> > On Mon, 2025-01-20 at 16:45 -0500, Corey Huinker wrote:
>> > >
>> > > What I struggle to understand is how that purpose isn't served better
>> > > by statistics being in SECTION_NONE like COMMENTs are, so that they
>> > > are imported immediately after the object that they reference.
>> >
>> > Tom, you expressed the strongest opinions on this point, can you expand
>> > a bit?
>> >
>> > If I understand correctly:
>> >
>> > * We strongly want stats to be exported by default[1].
>> >
>> > * Adding a SECTION_STATS could work, but would be non-trivial and might
>> > break expectations about the set of sections available[2].
>> >
>> > * SECTION_NONE doesn't seem right. There would be no way to get the
>> > stats using --section. Also, if there is no section boundary for the
>> > stats, then couldn't they appear in a surprising order?
>> >
>> > * I'm not sure about placing stats in SECTION_POST_DATA. That doesn't
>> > seem terrible to me, but not great either.
>> >
>>
>> index is on SECTION_POST_DATA.
>> To dump all the statistics, we have to go through SECTION_POST_DATA.
>> place it there would be more convenient.
>>
>
> That would be the simpler solution, but those statistics may come in handy
> for refreshing mviews, so some may want table stats to stay in SECTION_DATA.
>
>
>>
>> Tomas Vondra also mentioned this on [1]
>> [1]
>> https://www.postgresql.org/message-id/bf724b21-914a-4497-84e3-49944f9776f6%40enterprisedb.com
>>
>> > * I'm also not 100% sure about the flags. The default should dump the
>> > stats, of course. And I like the idea of allowing any combination of
>> > schema, data and stats to be exported. But that leaves a wrinkle for --
>> > data-only, which (as of v38) does not dump stats, because stats are a
>> > third kind of thing. Perhaps stats should be expressed as a subtype of
>> > data somehow, but I'm not sure exactly how.
>> >
>> if we have --data-only, --schema-only, --statistics-only, three options,
>> then
>> --data-only also dump statistics would be unintuitive?
>>
>
> Yeah, I think the codebase and the user flags both have confusing bits
> where the not-wanting of one type of thing was specified by only-wanting
> the other thing, and those choices fall apart when the binary becomes
> trinary.
>


Seems I also replied only to Micahel with the v45 patch.

And here's an update to the pg_dump code itself. This currently has failing
TAP tests for statistics in the custom and dir formats, but is working
otherwise.