Horton

Re: Statistics Import and Export

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Corey Huinker <corey.huinker@gmail.com>, jian he <jian.universality@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: 2025-02-07T06:07:18Z
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 Wed, Feb 05, 2025 at 08:45:06PM -0800, Jeff Davis wrote:
> v45-0001 addresses this by locking both the partitioned index, as well
> as its table, in ShareUpdateExclusive mode. That satisfies the in-place
> update requirement to take a ShareUpdateExclusiveLock on the
> partitioned index, while otherwise being the same as normal indexes
> (and therefore unlikely to cause a problem if ANALYZE sets stats on
> partitioned indexes in the future).
> 
> That means:
>   * For indexes: ShareUpdateExclusiveLock on table and AccessShareLock
> on index
>   * For partitioned indexes: ShareUpdateExclusiveLock on table and
> ShareUpdateExclusiveLock on index
>   * Otherwise, ShareupdateExclusiveLock on the relation
> 
> which makes sense to me. The v45-0001 patch itself could use some
> cleanup, but I can take care of that at commit time if we agree on the
> locking scheme.

Fine by me.

The regression tests of v45 and v46 are a bit fuzzy regarding the
tests around locking for partitioned tables.  For example, with v46
applied on top of HEAD, if I manipulate the internals of the patch in
stats_check_arg_pair() so as we don't take a lock on the parent table,
then a make check is still happy and passes even if the internals are
clearly broken.

I would recommend to work a bit more the tests by updating the stats
of a relation with the SQL functions in a transaction and add some
queries on pg_locks for locktype = 'relation' that are able to check
the locks we are taking when running these operations (return pairs of
relation::regclass and mode, for example).  Doing that for
non-partitioned relations is also something I would do, so as the
locking schema we are using is clearly tracked and that future
manipulations of the area would help one in tracking problems.  Bonus
points: scans of pg_locks are cheap tests.
--
Michael