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: 2024-04-02T21:31:07Z
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:
> On the export side, the problem is that the element type (and
> dimensionality and maybe hasnull) is an important part of the anyarray
> value, but it's not part of the output of anyarray_out(). For new
> versions, we can add a scalar function that simply outputs the
> information we need. For old versions, we can hack it by parsing the
> output of anyarray_send(), which contains the information we need
> (binary outputs are under-specified, but I believe they are specified
> enough in this case).

Yeah, I was thinking yesterday about pulling the anyarray columns in
binary and looking at the header fields.  However, I fear there is a
showstopper problem: anyarray_send will fail if the element type
doesn't have a typsend function, which is entirely possible for
user-defined types (and I'm not even sure we've provided them for
every type in the core distro).  I haven't thought of a good answer
to that other than a new backend function.  However ...

> On the import side, the problem is that there may not be an input
> function to go from a 1-D array of text to a 1-D array of any element
> type we want. For example, there's no input function that will create a
> 1-D array with element type float4[] (that's because Postgres doesn't
> really have arrays-of-arrays, it has multi-dimensional arrays).
> Instead, don't use the input function, pass each element of the 1-D
> text array to the element type's input function (which may be scalar or
> not) and then construct a 1-D array out of that with the appropriate
> element type (which may be scalar or not).

Yup.  I had hoped that we could avoid doing any array-munging inside
pg_set_attribute_stats, but this array-of-arrays problem seems to
mean we have to.  In turn, that means that the whole idea of
declaring the function inputs as anyarray rather than text[] is
probably pointless.  And that means that we don't need the sending
side to know the element type anyway.  So, I apologize for sending
us down a useless side path.  We may as well stick to the function
signature as shown in the v15 patch --- although maybe variadic
any is still worthwhile so that an unrecognized field name doesn't
need to be a hard error?

			regards, tom lane