Horton

Re: cataloguing NOT NULL constraints

Isaac Morland <isaac.morland@gmail.com>

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From: Isaac Morland <isaac.morland@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-09-20T14:15:29Z
Lists: pgsql-hackers

Commits

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  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 Tue, 20 Sept 2022 at 06:56, Alvaro Herrera <alvherre@alvh.no-ip.org>
wrote:

The NULL checks would still be mostly done by the attnotnull checks
> internally, so there shouldn't be too much of a difference.
>
> .. though I'm now wondering if there's additional overhead from checking
> the constraint twice on each row: first the attnotnull bit, then the
> CHECK itself.  Hmm.  That's probably quite bad.
>

Another reason to treat NOT NULL-implementing constraints differently.

My thinking is that pg_constraint entries for NOT NULL columns are mostly
an implementation detail. I've certainly never cared whether I had an
actual constraint corresponding to my NOT NULL columns. So I think marking
them as such, or a different contype, and excluding them from \d+ display,
probably makes sense. Just need to deal with the issue of trying to create
a constraint and having its name conflict with a NOT NULL constraint. Could
it work to reserve [field name]_notnull for NOT NULL-implementing
constraints? I'd be worried about what happens with field renames; renaming
the constraint automatically seems a bit weird, but maybe…