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: 2023-08-09T07:55:09Z
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 05.08.23 21:50, Dean Rasheed wrote:
>> Anyway, I was at the same time fixing the other problem you reported
>> with inheritance (namely, adding a PK ends up with the child column
>> being marked NOT NULL but no corresponding constraint).
>>
>> At some point I wondered if the easy way out wouldn't be to give up on
>> the idea that creating a PK causes the child columns to be marked
>> not-nullable.  However, IIRC I decided against that because it breaks
>> restoring of old dumps, so it wouldn't be acceptable.
>>
>> To make matters worse: pg_dump creates the PK as
>>
>>    ALTER TABLE ONLY parent ADD PRIMARY KEY ( ... )
>>
>> note the ONLY there.  It seems I'm forced to cause the PK to affect
>> children even though ONLY is given.  This is undesirable but I don't see
>> a way out of that.
>>
>> It is all a bit of a rat's nest.
>>
> 
> I wonder if that could be made to work in the same way as inherited
> CHECK constraints -- dump the child's inherited NOT NULL constraints,
> and then manually update conislocal in pg_constraint.

I wonder whether the root of these problems is that we mix together 
primary key constraints and not-null constraints.  I understand that 
right now, with the proposed patch, when a table inherits from a parent 
table with a primary key constraint, we generate not-null constraints on 
the child, in order to enforce the not-nullness.  What if we did 
something like this instead: In the child table, we don't generate a 
not-null constraint, but instead a primary key constraint entry.  But we 
mark the primary key constraint somehow to say, this is just for the 
purpose of inheritance, don't enforce uniqueness, but enforce 
not-nullness.  Would that work?