Horton

Re: cataloguing NOT NULL constraints

Alvaro Herrera <alvherre@alvh.no-ip.org>

View thread
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, exclusion@gmail.com, dean.a.rasheed@gmail.com, andrewbille@gmail.com, peter@eisentraut.org, pgsql-hackers@lists.postgresql.org, Justin Pryzby <pryzby@telsasoft.com>
Date: 2024-05-11T09:40:01Z
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. Revert structural changes to not-null constraints

  2. Fix inconsistencies in error messages

  3. Disallow direct change of NO INHERIT of not-null constraints

  4. Disallow NO INHERIT not-null constraints on partitioned tables

  5. Better handle indirect constraint drops

  6. Don't try to assign smart names to constraints

  7. Fix restore of not-null constraints with inheritance

  8. ATTACH PARTITION: Don't match a PK with a UNIQUE constraint

  9. Fix propagating attnotnull in multiple inheritance

  10. Check stack depth in new recursive functions

  11. Move privilege check to the right place

  12. Update information_schema definition for not-null constraints

  13. Fix not-null constraint test

  14. Disallow changing NO INHERIT status of a not-null constraint

  15. Catalog not-null constraints

  16. parallel_schedule: add comment on event_trigger test dependency

  17. Revert "Catalog NOT NULL constraints" and fallout

  18. Adjust contrib/sepgsql regression test expected outputs.

  19. Fix table name clash in recently introduced test

  20. Catalog NOT NULL constraints

  21. Change the rules for inherited CHECK constraints to be essentially the same

On 2024-May-09, Robert Haas wrote:

> Yeah, I have to admit that the ongoing bug fixing here has started to
> make me a bit nervous, but I also can't totally follow everything
> that's under discussion, so I don't want to rush to judgement.

I have found two more problems that I think are going to require some
more work to fix, so I've decided to cut my losses now and revert the
whole.  I'll come back again in 18 with these problems fixed.

Specifically, the problem is that I mentioned that we could restrict the
NOT NULL NO INHERIT addition in pg_dump for primary keys to occur only
in pg_upgrade; but it turns this is not correct.  In normal
dump/restore, there's an additional table scan to check for nulls when
the constraints is not there, so the PK creation would become measurably
slower.  (In a table with a million single-int rows, PK creation goes
from 2000ms to 2300ms due to the second scan to check for nulls).

The addition of NOT NULL NO INHERIT constraints for this purpose
collides with addition of constraints for other reasons, and it forces
us to do unpleasant things such as altering an existing constraint to go
from NO INHERIT to INHERIT.  If this happens only during pg_upgrade,
that would be okay IMV; but if we're forced to allow in normal operation
(and in some cases we are), it could cause inconsistencies, so I don't
want to do that.  I see a way to fix this (adding another query in
pg_dump that detects which columns descend from ones used in PKs in
ancestor tables), but that's definitely too much additional mechanism to
be adding this late in the cycle.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/