Horton

Re: Extended Statistics set/restore/clear functions.

jian he <jian.universality@gmail.com>

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From: jian he <jian.universality@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Corey Huinker <corey.huinker@gmail.com>, Tomas Vondra <tomas@vondra.me>, pgsql-hackers@lists.postgresql.org, tgl@sss.pgh.pa.us
Date: 2025-11-12T02:51:51Z
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. Add test doing some cloning of extended statistics data

  2. Add test for pg_restore_extended_stats() with multiranges

  3. Add support for "mcv" in pg_restore_extended_stats()

  4. Include extended statistics data in pg_dump

  5. Add support for "dependencies" in pg_restore_extended_stats()

  6. Add test for MAINTAIN permission with pg_restore_extended_stats()

  7. Add pg_restore_extended_stats()

  8. Add routine to free MCVList

  9. Improve pg_clear_extended_stats() with incorrect relation/stats combination

  10. Add pg_clear_extended_stats()

  11. Introduce routines to validate and free MVNDistinct and MVDependencies

  12. Fix typo in stat_utils.c

  13. Move attribute statistics functions to stat_utils.c

  14. Improve error messages of input functions for pg_dependencies and pg_ndistinct

  15. Improve test output of extended statistics for ndistinct and dependencies

  16. Fix some compiler warnings

  17. Add input function for data type pg_dependencies

  18. Add input function for data type pg_ndistinct

  19. Rework output format of pg_dependencies

  20. Rework output format of pg_ndistinct

  21. Fix comments of output routines for pg_ndistinct and pg_dependencies

  22. Move code specific to pg_dependencies to new file

  23. Move code specific to pg_ndistinct to new file

  24. Document some structures in attribute_stats.c

  25. Fix FATAL message for invalid recovery timeline at beginning of recovery

On Tue, Nov 11, 2025 at 11:14 PM jian he <jian.universality@gmail.com> wrote:
>
> On Tue, Nov 11, 2025 at 4:07 PM Michael Paquier <michael@paquier.xyz> wrote:
> > I've rebased the full set using the new structure.  0001~0004 are
> > clean.  0005~ need more work and analysis, but that's a start.

hi.

+Datum
+pg_ndistinct_out(PG_FUNCTION_ARGS)
+
+
+ appendStringInfo(&str, "], \"" PG_NDISTINCT_KEY_NDISTINCT "\": %d}",
+ (int) item.ndistinct);

I’m a bit confused about the part above,
item.ndistinct is double type, we just cast it to int type?


after apply 0004, the below in doc/src/sgml/perform.sgml also need to change?

<programlisting>
CREATE STATISTICS stts (dependencies) ON city, zip FROM zipcodes;

ANALYZE zipcodes;

SELECT stxname, stxkeys, stxddependencies
  FROM pg_statistic_ext join pg_statistic_ext_data on (oid = stxoid)
  WHERE stxname = 'stts';
 stxname | stxkeys |             stxddependencies
---------+---------+------------------------------------------
 stts    | 1 5     | {"1 => 5": 1.000000, "5 => 1": 0.423130}
(1 row)
</programlisting>


Do you think it's worth the trouble to have two separate
appendStringInfoChar for ``{}``?

for example in loop ``for (i = 0; i < ndist->nitems; i++)``. we can change to:
        appendStringInfoChar(&str, '{');
        appendStringInfo(&str, "\"" PG_NDISTINCT_KEY_ATTRIBUTES "\": [%d",
                         item.attributes[0]);

        for (int j = 1; j < item.nattributes; j++)
            appendStringInfo(&str, ", %d", item.attributes[j]);

        appendStringInfo(&str, "], \"" PG_NDISTINCT_KEY_NDISTINCT "\": %d",
                         (int) item.ndistinct);
        appendStringInfoChar(&str, '}');


--
jian
https://www.enterprisedb.com/