Horton

Re: cataloguing NOT NULL constraints

Matthias van de Meent <boekewurm+postgres@gmail.com>

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From: Matthias van de Meent <boekewurm+postgres@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Pg Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-09-19T14:10:17Z
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 Mon, 19 Sept 2022 at 15:32, 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'm not sure on the 'good' part of this alternative, but we could go
with a single row-based IS NOT NULL to reduce such clutter, utilizing
the `ROW() IS NOT NULL` requirement of a row only matching IS NOT NULL
when all attributes are also IS NOT NULL:

    Check constraints:
        "tab_notnull_check" CHECK (ROW(a, b, c, d, e) IS NOT NULL)

instead of:

    Check constraints:
        "tab_a_not_null" CHECK (a IS NOT NULL)
        "tab_b_not_null" CHECK (b IS NOT NULL)
        "tab_c_not_null" CHECK (c IS NOT NULL)
        "tab_d_not_null" CHECK (d IS NOT NULL)
        "tab_e_not_null" CHECK (e IS NOT NULL)

But the performance of repeated row-casting would probably not be as
good as our current NULL checks if we'd use the current row
infrastructure, and constraint failure reports wouldn't be as helpful
as the current attribute NOT NULL failures.

Kind regards,

Matthias van de Meent