Horton

Re: cataloguing NOT NULL constraints

Isaac Morland <isaac.morland@gmail.com>

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From: Isaac Morland <isaac.morland@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Pg Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-09-19T13:54:41Z
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 Mon, 19 Sept 2022 at 09:32, Robert Haas <robertmhaas@gmail.com> wrote:

> On Wed, Aug 17, 2022 at 2:12 PM Alvaro Herrera <alvherre@alvh.no-ip.org>
> wrote:
> > If you say CREATE TABLE (a int NOT NULL), you'll get a CHECK constraint
> > printed by psql: (this is a bit more noisy that previously and it
> > changes a lot of regression tests output).
> >
> > 55489 16devel 1776237=# create table tab (a int not null);
> > CREATE TABLE
> > 55489 16devel 1776237=# \d tab
> >                     Tabla «public.tab»
> >  Columna │  Tipo   │ Ordenamiento │ Nulable  │ Por omisión
> > ─────────┼─────────┼──────────────┼──────────┼─────────────
> >  a       │ integer │              │ not null │
> > Restricciones CHECK:
> >     "tab_a_not_null" CHECK (a IS NOT NULL)
>
> In a table with many columns, most of which are NOT NULL, this is
> going to produce a ton of clutter. I don't like that.
>
> I'm not sure what a good alternative would be, though.
>

I thought I saw some discussion about the SQL standard saying that there is
a difference between putting NOT NULL in a column definition, and CHECK
(column_name NOT NULL). So if we're going to take this seriously, I think
that means there needs to be a field in pg_constraint which identifies
whether a constraint is a "real" one created explicitly as a constraint, or
if it is just one created because a field is marked NOT NULL.

If this is correct, the answer is easy: don't show constraints that are
there only because of a NOT NULL in the \d or \d+ listings. I certainly
don't want to see that clutter and I'm having trouble seeing why anybody
else would want to see it either; the information is already there in the
"Nullable" column of the field listing.

The error message for a duplicate constraint name when creating a
constraint needs however to be very clear that the conflict is with a NOT
NULL constraint and which one, since I'm proposing leaving those ones off
the visible listing, and it would be very bad for somebody to get
"duplicate name" and then be unable to see the conflicting entry.