Re: information_schema and not-null constraints

Peter Eisentraut <peter@eisentraut.org>

From: Peter Eisentraut <peter@eisentraut.org>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>, Pg Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-09-06T11:02:50Z
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 05.09.23 18:24, Alvaro Herrera wrote:
> On 2023-Sep-05, Peter Eisentraut wrote:
> 
>> The following information schema views are affected by the not-null
>> constraint catalog entries:
>>
>> 1. CHECK_CONSTRAINTS
>> 2. CONSTRAINT_COLUMN_USAGE
>> 3. DOMAIN_CONSTRAINTS
>> 4. TABLE_CONSTRAINTS
>>
>> Note that 1 and 3 also contain domain constraints.
> 
> After looking at what happens for domain constraints in older versions
> (I tested 15, but I suppose this applies everywhere), I notice that we
> don't seem to handle them anywhere that I can see.  My quick exercise is
> just
> 
> create domain nnint as int not null;
> create table foo (a nnint);
> 
> and then verify that this constraint shows nowhere -- it's not in
> DOMAIN_CONSTRAINTS for starters, which is I think the most obvious place.
> And nothing is shown in CHECK_CONSTRAINTS nor TABLE_CONSTRAINTS either.
> 
> This did ever work in the past?  I tested with 9.3 and didn't see
> anything there either.

No, this was never implemented.  (As I wrote in my other message on the 
other thread, arguably a bit buggy.)  We could fix this separately, 
unless we are going to implement catalogued domain not-null constraints 
soon.