Horton

Re: Statistics Import and Export

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: Corey Huinker <corey.huinker@gmail.com>
Cc: 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>, 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: 2025-02-13T03:00:55Z
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, 2025-02-11 at 14:02 -0500, Corey Huinker wrote:
> 
> 
> The previous 0001 is now committed (thanks!) so only one remains.
>  

Summary of the decisions made in this thread:

  * pg_dump --data-only does not include stats[1]. This behavior was
    not fully resolved, but I didn't see a reasonable set of options
    where (a) --data-only would include stats; and (b) we could
    specify what pg_upgrade needs, which is schema+stats. Jian seemed
    to agree. However, this leaves us with the behavior where
    --data-only doesn't get everything in SECTION_DATA, which might be
    undesirable.
  * stats are in SECTION_DATA[2], except for stats on objects that
    are created in SECTION_POST_DATA, in which case the stats are
    also in SECTION_POST_DATA
    - indexes are created in SECTION_POST_DATA, and though plain
      indexes don't have stats, expression indexes do
    - MVs are normally created in SECTION_PRE_DATA, in which case
      the stats are in SECTION_DATA; but MVs can be deferred to
      SECTION_POST_DATA due to dependency on a primary key
  * SECTION_NONE was proposed, but rejected[2]
  * The default is to include the stats.[3]
  * pg_dump[all] options are designed to allow specifying any
    combination of schema[4], data, and stats:
      --schema-only (schema), --no-schema (data+stats)
      --data-only (data), --no-data (schema+stats)
      --stats-only (stats), --no-stats (schema+data)
  * A SECTION_STATS was proposed and rejected due to complexity[5]
  * The prefix in the dump output will be "Statistics for " (instead
    of "Data for ")[6]
  * The TOC description will be "STATISTICS DATA", differentiating
    it from an extended statistics object[6]
  * pg_upgrade will now pass --no-data (schema+stats) to pg_dump
    instead of --schema-only, thereby transferring the stats to the
    new cluster[7]

It's been a long thread, so please tell me if I missed something or if
something needs more discussion.

I'm still reviewing v48, but I intend to commit something soon.

Regards,
	Jeff Davis

[1]
https://www.postgresql.org/message-id/b40b81d38c3a87fdef61e4f7abfbc7f27c7fbcd9.camel@j-davis.com

[2] 
https://www.postgresql.org/message-id/1798867.1712376328%40sss.pgh.pa.us

[3]
https://www.postgresql.org/message-id/3228677.1713844341%40sss.pgh.pa.us

[4]
https://www.postgresql.org/message-id/CACJufxG6K4EAUROhdr0wkzMh5QyFLmdLZeAoh7Vh0-VbuAtHcw%40mail.gmail.com

[5]
https://www.postgresql.org/message-id/3156140.1713817153%40sss.pgh.pa.us

[6] 
https://www.postgresql.org/message-id/d8df5339cab25b5720667beaaed8a8bb8e11578c.camel@j-davis.com

[7]
https://www.postgresql.org/message-id/c2bc08dfec336c03f7a7165d1347e2b52cf98b17.camel@j-davis.com