Horton

Re: cataloguing NOT NULL constraints

Peter Eisentraut <peter@eisentraut.org>

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From: Peter Eisentraut <peter@eisentraut.org>
To: Dean Rasheed <dean.a.rasheed@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2023-08-16T08:02:11Z
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 15.08.23 11:57, Dean Rasheed wrote:
> Something else I noticed when reading the SQL standard is that a
> user-defined CHECK (col IS NOT NULL) constraint should be recognised
> by the system as also making the column not null (setting its
> "nullability characteristic" to "known not nullable"). I think that's
> more than just an artefact of how they say NOT NULL constraints should
> be implemented, because the effect of such a CHECK constraint should
> be exposed in the "columns" view of the information schema -- the
> value of "is_nullable" should be "NO" if the column is "known not
> nullable".

Nullability determination is different from not-null constraints.  The 
nullability characteristic of a column can be derived from multiple 
sources, including not-null constraints, check constraints, primary key 
constraints, domain constraints, as well as more complex rules in case 
of views, joins, etc.  But this is all distinct and separate from the 
issue of not-null constraints that we are discussing here.