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: Andres Freund <andres@anarazel.de>, Corey Huinker <corey.huinker@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Michael Paquier <michael@paquier.xyz>, 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: 2025-02-25T03:30:12Z
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 5:01 AM Jeff Davis <pgsql@j-davis.com> wrote:
>
> On Mon, 2025-02-24 at 15:53 -0500, Andres Freund wrote:
> > I don't think that's necessarily true, hot pruning might help some,
> > as afaict
> > the restore happens in multiple transactions.
>
> Yeah, I just dumped and reloaded the regression database with and
> without stats, and saw no difference in the resulting size. So it's
> probably more correct to say "churn" rather than "bloat".
>
> Even running "psql -1", I see modest bloat substantially less than 2x.
>
> So if we agree that we don't mind a bit of churn and we will never need
> this (despite what ANALYZE does), then I'm OK removing it. Which makes
> me wonder why ANALYZE does it with inplace updates?
>

hi.
looking at commit:
https://git.postgresql.org/cgit/postgresql.git/commit/?id=f3dae2ae5856dec9935a51e53216400566ef8d4f

I am confused by this:
```
    ctup = SearchSysCache1(RELOID, ObjectIdGetDatum(reloid));
    if (!HeapTupleIsValid(ctup))
    {
        ereport(elevel,
                (errcode(ERRCODE_OBJECT_IN_USE),
                 errmsg("pg_class entry for relid %u not found", reloid)));
        table_close(crel, RowExclusiveLock);
        return false;
    }
```
First I thought ERRCODE_OBJECT_IN_USE was weird. maybe
ERRCODE_NO_DATA_FOUND would be more appropriate.

then but ``stats_lock_check_privileges(reloid);`` already proves there is
a pg_class entry for reloid.
maybe we can just use
elog(ERROR, "pg_class entry for relid %u not found", reloid)));


also in stats_lock_check_privileges.
check_inplace_rel_lock related comments should be removed?