Horton

Re: Statistics Import and Export

Corey Huinker <corey.huinker@gmail.com>

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From: Corey Huinker <corey.huinker@gmail.com>
To: Matthias van de Meent <boekewurm+postgres@gmail.com>
Cc: Bruce Momjian <bruce@momjian.us>, Tom Lane <tgl@sss.pgh.pa.us>, Jeff Davis <pgsql@j-davis.com>, Nathan Bossart <nathandbossart@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>, Tomas Vondra <tomas.vondra@enterprisedb.com>
Date: 2024-05-07T03:43:50Z
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.

Attachments

>
>
> Next up for question is how to handle --statistics-only or an equivalent.
> The option would be mutually exclusive with --schema-only and --data-only,
> and it would be mildly incongruous if it didn't have a short option like
> the others, so I'm suggested -P for Probablity / Percentile / ρ:
> correlation / etc.
>
> One wrinkle with having three mutually exclusive options instead of two is
> that the existing code was able to assume that one of the options being
> true meant that we could bail out of certain dumpXYZ() functions, and now
> those tests have to compare against two, which makes me think we should add
> three new DumpOptions that are the non-exclusive positives (yesSchema,
> yesData, yesStats) and set those in addition to the schemaOnly, dataOnly,
> and statsOnly flags. Thoughts?
>

v21 attached.

0001 is the same.

0002 is a preparatory change to pg_dump introducing
DumpOption/RestoreOption variables dumpSchema and dumpData. The current
code makes heavy use of the fact that schemaOnly and dataOnly are mutually
exclusive and logically opposite. That will not be the case when
statisticsOnly is introduced, so I decided to add the new variables whose
value is entirely derivative of the existing command flags, but resolves
the complexities of those interactions in one spot, as those complexities
are about to jump with the new options.

0003 is the statistics changes to pg_dump, adding the options -X /
--statistics-only, and the derivative boolean statisticsOnly. The -P option
is already used by pg_restore, so instead I chose -X because of the passing
resemblance to Chi as in the chi-square statistics test makes it vaguely
statistics-ish. If someone has a better letter, I'm listening.

With that change, people should be able to use pg_dump -X --table=foo to
dump existing stats for a table and its dependent indexes, and then tweak
those calls to do tuning work. Have fun with it. If this becomes a common
use-case then it may make sense to get functions to fetch
relation/attribute stats for a given relation, either as a formed SQL
statement or as the parameter values.