BUG #19024: Error when trying to use pg_dump of new server on old server

The following bug has been logged on the website:

Bug reference:      19024
Logged by:          Egor Chindyaskin
Email address:      kyzevan23@mail.ru
PostgreSQL version: 17.6
Operating system:   Ubuntu 25.04
Description:

Hello, commit 6b755d8d70b2ceffeb4798cbb6907d2704c2e6c4 introduced a new bug.
If you take the old cluster and server and try to do a pg_dump on the new
server REL_17_STABLE (71ee96e9f95806f9f6e2c805496c0dcf25b3946a), as shown in
the reproduction below:

#!/bin/bash
PG_OLD=REL_17_0/bin
PG_NEW=REL_17_STABLE/bin
$PG_OLD/initdb -D data
$PG_OLD/pg_ctl -D data -l logfile start
$PG_OLD/dropdb testdb > /dev/null || true
$PG_OLD/createdb testdb
$PG_OLD/psql -c "CREATE DOMAIN public.hstestdom1 AS integer NOT NULL DEFAULT
0;" testdb
$PG_NEW/pg_dump testdb

We will get the error

pg_dump: error: query failed: ERROR:  invalid constraint type "n"
pg_dump: detail: Query was: EXECUTE getDomainConstraints('16386')

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Best regards,
Egor Chindyaskin
Postgres Professional: http://postgrespro.com