Horton

Re: Catalog domain not-null constraints

Peter Eisentraut <peter@eisentraut.org>

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From: Peter Eisentraut <peter@eisentraut.org>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2023-11-27T07:08:08Z
Lists: pgsql-hackers

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  1. Fix ALTER DOMAIN NOT NULL syntax

  2. Catalog domain not-null constraints

  3. Add tests for domain-related information schema views

On 23.11.23 17:38, Alvaro Herrera wrote:
> If you create a table with column of domain that has a NOT NULL
> constraint, what happens?  I mean, is the table column marked
> attnotnull, and how does it behave?

No, the domain does not affect the catalog entry for the column.  This 
is the same way it behaves now.

> Is there a separate pg_constraint
> row for the constraint in the table?  What happens if you do
> ALTER TABLE ... DROP NOT NULL for that column?

Those are separate.  After dropping the NOT NULL for a column, null 
values for the column could still be rejected by a domain.  (This is the 
same way CHECK constraints work.)