Horton

Re: Statistics Import and Export

jian he <jian.universality@gmail.com>

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From: jian he <jian.universality@gmail.com>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Corey Huinker <corey.huinker@gmail.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: 2025-01-27T14:05:06Z
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, 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.

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?