From: Tom Lane <tgl@sss.pgh.pa.us>
To: "David G. Johnston" <david.g.johnston@gmail.com>
cc: dafoer_x@163.com,
        PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #17464: Domain type. If the value field(CREATE DOMAIN) is set
 to null, errors cannot be intercepted.
In-reply-to: 
 <CAKFQuwYwhyZDkR2RmQ8ns7p=gVjBumU_Broh_VC9JMTkOpcotA@mail.gmail.com>
References: <17464-4751c9d69159f363@postgresql.org>
 <CAKFQuwYwhyZDkR2RmQ8ns7p=gVjBumU_Broh_VC9JMTkOpcotA@mail.gmail.com>
Comments: In-reply-to "David G. Johnston" <david.g.johnston@gmail.com>
	message dated "Tue, 12 Apr 2022 07:27:44 -0700"
MIME-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-ID: <795092.1649774506.1@sss.pgh.pa.us>
Content-Transfer-Encoding: quoted-printable
Date: Tue, 12 Apr 2022 10:41:46 -0400
Message-ID: <795093.1649774506@sss.pgh.pa.us>
Archived-At: 
 <https://www.postgresql.org/message-id/795093.1649774506%40sss.pgh.pa.us>
Precedence: bulk

"David G. Johnston" <david.g.johnston@gmail.com> writes:
> "VALUES =3D null" is simply wrong.  That isn't how one checks for null. =
 Use
> "IS NULL".  If that restores the correct behavior I'm unsure what we'd b=
e
> willing to do to behave differently in the presence of the improper null
> test form.

There's already transform_null_equals, which does work if you turn it on
while executing this incorrect CREATE DOMAIN command.  But the better
answer is to fix your SQL.

regression=3D# set transform_null_equals =3D 1;
SET
regression=3D# CREATE DOMAIN xb AS TEXT CHECK
regression-# (
regression(#    VALUE =3D '=E7=94=B7'
regression(#    OR VALUE =3D'=E5=A5=B3'
regression(#    OR VALUE =3D null
regression(#  );
CREATE DOMAIN
regression=3D# \dD+ xb
                                                                       Lis=
t of domains
 Schema | Name | Type | Collation | Nullable | Default |                  =
             Check                                | Access privileges | De=
scription =

--------+------+------+-----------+----------+---------+------------------=
--------------------------------------------------+-------------------+---=
----------
 public | xb   | text |           |          |         | CHECK (VALUE =3D =
'=E7=94=B7'::text OR VALUE =3D '=E5=A5=B3'::text OR VALUE IS NULL) |      =
             | =

(1 row)


			regards, tom lane