Обсуждение: BUG #19444: conkey field empty for domain NOT NULL constraint in pg_constraint (18.3)

The following bug has been logged on the website:

Bug reference:      19444
Logged by:          Xianghang Zheng
Email address:      zheng_xianghang@163.com
PostgreSQL version: 18.3
Operating system:   Linux x86_64
Description:

When creating a domain with a NOT NULL constraint, the conkey field in
pg_constraint remains empty. This is inconsistent with table-level NOT
NULL constraints, which correctly populate the conkey field.

Version: PostgreSQL 18.3 (x86_64)
Platform: Linux x86_64

Steps to Reproduce:
-------------------
CREATE DOMAIN my_domain AS text NOT NULL;

SELECT conname, contype, conkey, contypid::regtype
FROM pg_constraint
WHERE contypid = 'my_domain'::regtype;

Actual Result:
--------------
      conname       | contype | conkey | contypid
--------------------+---------+--------+-----------
 my_domain_not_null | n       |        | my_domain
(1 row)

Expected Result:
----------------
The conkey field should contain {1} (the first and only column of the
domain):

      conname       | contype | conkey | contypid
--------------------+---------+--------+-----------
 my_domain_not_null | n       | {1}    | my_domain

Additional Information:
-----------------------
- The NOT NULL constraint works correctly (rejects NULL values)
- The issue is only with the system catalog metadata
- This may affect tools like pg_dump, pg_upgrade, or extensions that rely
  on the conkey field for domain constraints
- Table-level NOT NULL constraints correctly populate conkey:

  CREATE TABLE test_table (id text NOT NULL);
  SELECT conname, contype, conkey FROM pg_constraint
  WHERE conrelid = 'test_table'::regclass;

  Result: test_table_id_not_null | n | {1}

Please let me know if you need any additional information or testing.

On Mon, Mar 30, 2026 at 7:52 PM PG Bug reporting form
<noreply@postgresql.org> wrote:
>
> The following bug has been logged on the website:
>
> Bug reference:      19444
> Logged by:          Xianghang Zheng
> Email address:      zheng_xianghang@163.com
> PostgreSQL version: 18.3
> Operating system:   Linux x86_64
> Description:
>
> When creating a domain with a NOT NULL constraint, the conkey field in
> pg_constraint remains empty. This is inconsistent with table-level NOT
> NULL constraints, which correctly populate the conkey field.
>
> Version: PostgreSQL 18.3 (x86_64)
> Platform: Linux x86_64
>
> Steps to Reproduce:
> -------------------
> CREATE DOMAIN my_domain AS text NOT NULL;
>
> SELECT conname, contype, conkey, contypid::regtype
> FROM pg_constraint
> WHERE contypid = 'my_domain'::regtype;
>
> Actual Result:
> --------------
>       conname       | contype | conkey | contypid
> --------------------+---------+--------+-----------
>  my_domain_not_null | n       |        | my_domain
> (1 row)
>
> Expected Result:
> ----------------
> The conkey field should contain {1} (the first and only column of the
> domain):
>
>       conname       | contype | conkey | contypid
> --------------------+---------+--------+-----------
>  my_domain_not_null | n       | {1}    | my_domain
>
> Additional Information:
> -----------------------
> - The NOT NULL constraint works correctly (rejects NULL values)
> - The issue is only with the system catalog metadata
> - This may affect tools like pg_dump, pg_upgrade, or extensions that rely
>   on the conkey field for domain constraints
> - Table-level NOT NULL constraints correctly populate conkey:
>
>   CREATE TABLE test_table (id text NOT NULL);
>   SELECT conname, contype, conkey FROM pg_constraint
>   WHERE conrelid = 'test_table'::regclass;
>
>   Result: test_table_id_not_null | n | {1}
>
> Please let me know if you need any additional information or testing.
>
>

I think you have interpreted this incorrectly, domain is a type, not a relation.
See the comments in pg_constraint.h for clarification.

/*
* conrelid and conkey are only meaningful if the constraint applies to a
* specific relation (this excludes domain constraints and assertions).
* Otherwise conrelid is 0 and conkey is NULL.
*/

>
>


--
Regards
Junwang Zhao

PG Bug reporting form <noreply@postgresql.org> writes:
> When creating a domain with a NOT NULL constraint, the conkey field in
> pg_constraint remains empty. This is inconsistent with table-level NOT
> NULL constraints, which correctly populate the conkey field.

I do not think this is a bug.  The system catalog documentation says

    conkey int2[] (references pg_attribute.attnum)

      If a table constraint (including foreign keys, but not
      constraint triggers), list of the constrained columns

So (a) this is not a table constraint, and (b) a domain does not have
columns.

            regards, tom lane