Horton

Re: Statistics Import and Export

Stephen Frost <sfrost@snowman.net>

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From: Stephen Frost <sfrost@snowman.net>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Corey Huinker <corey.huinker@gmail.com>, Peter Smith <smithpb2250@gmail.com>, Tomas Vondra <tomas.vondra@enterprisedb.com>, pgsql-hackers@lists.postgresql.org
Date: 2024-03-01T17:16:51Z
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.

Greetings,

On Fri, Mar 1, 2024 at 12:14 Nathan Bossart <nathandbossart@gmail.com>
wrote:

> On Thu, Feb 29, 2024 at 10:55:20PM -0500, Corey Huinker wrote:
> >> That’s certainly a fair point and my initial reaction (which could
> >> certainly be wrong) is that it’s unlikely to be an issue- but also, if
> you
> >> feel you could make it work with an array and passing all the attribute
> >> info in with one call, which I suspect would be possible but just a bit
> >> more complex to build, then sure, go for it. If it ends up being overly
> >> unwieldy then perhaps the  per-attribute call would be better and we
> could
> >> perhaps acquire the lock before the function calls..?  Doing a check to
> see
> >> if we have already locked it would be cheaper than trying to acquire a
> new
> >> lock, I’m fairly sure.
> >
> > Well the do_analyze() code was already ok with acquiring the lock once
> for
> > non-inherited stats and again for inherited stats, so the locks were
> > already not the end of the world. However, that's at most a 2x of the
> > locking required, and this would natts * x, quite a bit more. Having the
> > procedures check for a pre-existing lock seems like a good compromise.
>
> I think this is a reasonable starting point.  If the benchmarks show that
> the locking is a problem, we can reevaluate, but otherwise IMHO we should
> try to keep it as simple/flexible as possible.


Yeah, this was my general feeling as well.  If it does become an issue, it
certainly seems like we would have ways to improve it in the future. Even
with this locking it is surely going to be better than having to re-analyze
the entire database which is where we are at now.

Thanks,

Stephen

>