Horton

Re: Statistics Import and Export

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Corey Huinker <corey.huinker@gmail.com>, Magnus Hagander <magnus@hagander.net>, Stephen Frost <sfrost@snowman.net>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Tomas Vondra <tomas.vondra@enterprisedb.com>
Date: 2024-04-06T04:05:28Z
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.

Jeff Davis <pgsql@j-davis.com> writes:
> Thank you, this has improved a lot and the fundamentals are very close.
> I think it could benefit from a bit more time to settle on a few
> issues:

Yeah ... it feels like we aren't quite going to manage to get this
over the line for v17.  We could commit with the hope that these
last details will get sorted later, but that path inevitably leads
to a mess.

> 1. SECTION_NONE. Conceptually, stats are more like data, and so
> intuitively I would expect this in the SECTION_DATA or
> SECTION_POST_DATA. However, the two most important use cases (in my
> opinion) don't involve dumping the data: pg_upgrade (data doesn't come
> from the dump) and planner simulations/repros. Perhaps the section we
> place it in is not a critical decision, but we will need to stick with
> it for a long time, and I'm not sure that we have consensus on that
> point.

I think it'll be a serious, serious error for this not to be
SECTION_DATA.  Maybe POST_DATA is OK, but even that seems like
an implementation compromise not "the way it ought to be".

> 2. We changed the stats import function API to be VARIADIC very
> recently. After we have a bit of time to think on it, I'm not 100% sure
> we will want to stick with that new API. It's not easy to document,
> which is something I always like to consider.

Perhaps.  I think the argument of wanting to be able to salvage
something even in the presence of unrecognized stats types is
stronger, but I agree this could use more time in the oven.
Unlike many other things in this patch, this would be nigh
impossible to reconsider later.

> 3. The error handling also changed recently to change soft errors (i.e.
> type input errors) to warnings. I like this change but I'd need a bit
> more time to get comfortable with how this is done, there is not a lot
> of precedent for doing this kind of thing.

I don't think there's much disagreement that that's the right thing,
but yeah there could be bugs or some more to do in this area.

			regards, tom lane