Horton

Re: Statistics Import and Export

Alvaro Herrera <alvherre@alvh.no-ip.org>

View thread
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Bruce Momjian <bruce@momjian.us>, Nathan Bossart <nathandbossart@gmail.com>, Magnus Hagander <magnus@hagander.net>, Corey Huinker <corey.huinker@gmail.com>, Jeff Davis <pgsql@j-davis.com>, jian he <jian.universality@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-11-27T18:05:51Z
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 2024-Nov-27, Tom Lane wrote:

> I do not like the idea of breaking existing upgrade scripts,
> especially not by requiring them to use a parameter that older
> vacuumdb versions will reject.  That makes it impossible to have a
> script that is version independent.  I really doubt that there is any
> usability improvement to be had here that's worth that.

I was only suggesting to break it because it was said upthread that that
was desirable behavior.

> How about causing "--analyze-in-stages" (as currently spelled) to
> be a no-op?  We could keep the behavior available under some other
> name.

I think making it a no-op isn't useful, because people who run the old
scripts will get the behavior we do not want: clobber the statistics and
recompute them, losing the benefit that this feature brings.

On 2024-Nov-27, Bruce Momjian wrote:

> Uh, I guess we could do that, but we should emit something like
> "--analyze-in-stages option ignored".

I think emitting a message is not useful.  It's quite possible that the
output of pg_upgrade will be redirected somewhere and this will go
unnoticed.


Maybe the most convenient for users is to keep "vacuumdb
--analyze-in-stages" doing exactly what we want to happen after
pg_upgrade, that is, in 18+, only recreate the missing stats.  This is
because of what Corey said about messaging: many users are not going to
get our message that they need to adapt their scripts, so they won't.
Breaking the script would convey that message pretty quickly, but you're
right that it's not very convenient.

For people that want to use the old behavior of recomputing _all_
statistics not just the missing ones, we could add a different switch,
or an (optional) option to --analyze-in-stages.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/