Horton

Re: Statistics Import and Export

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: Greg Sabino Mullane <htamfids@gmail.com>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Corey Huinker <corey.huinker@gmail.com>, Andres Freund <andres@anarazel.de>, 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>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, alvherre@alvh.no-ip.org, jian he <jian.universality@gmail.com>
Date: 2025-03-01T20:48:18Z
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 Sat, 2025-03-01 at 13:52 -0500, Greg Sabino Mullane wrote:
> > Can you expand on some of those cases?
> 
> Certainly. I think one of the problems is that because this patch is
> solving a pg_upgrade issue, the focus is on the "dump and restore"
> scenarios. But pg_dump is used for much more than that, especially
> "dump and examine".

Thank you for going through these examples.

> I just don't think it should be enabled by default for everything
> using pg_dump. For the record, I would not strongly object to having
> stats on by default for binary dumps, although I would prefer them
> off.

I am open to that idea, I just want to get it right, because probably
whatever the default is in 18 will stay that way.

Also, we will need to think through the set of pg_dump options again. A
lot of our tools seem to assume that "if it's the default, we don't
need a way to ask for it explicitly", which makes it a lot harder to
ever change the default and keep a coherent set of options.

> So why not just expect people to modify their programs to use --no-
> statistics for cases like this? That's certainly an option, but it's
> going to break a lot of existing things, and create branching code:

I suggest that we wait a bit to see what additional feedback we get
early in beta.

> Also, anything trained to parse pg_dump output will have to learn
> about the new SELECT pg_restore_ calls with their multi-line formats
> (not 100% sure we don't have that anywhere, as things like "SELECT
> setval" and "SELECT set_config" are single line, but there may be
> existing things)

That's an interesting point. What tools are currrently trying to parse
pg_dump output?

Regards,
	Jeff Davis