Feedback-ID: ia2694551:Fastmail
Date: Wed, 10 Apr 2024 13:01:52 +0200
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: jian he <jian.universality@gmail.com>
Cc: Tender Wang <tndrwang@gmail.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Can't find not null constraint, but \d+ shows that
Message-ID: <202404101101.c7brh2evkssj@alvherre.pgsql>
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On 2024-Apr-10, jian he wrote:

> another related bug, in master.
> 
> drop table if exists notnull_tbl1;
> CREATE TABLE notnull_tbl1 (c0 int not null, c1 int);
> ALTER TABLE notnull_tbl1 ADD CONSTRAINT Q PRIMARY KEY(c0, c1);
> \d+ notnull_tbl1
> ALTER TABLE notnull_tbl1 ALTER c0 DROP NOT NULL;
> ALTER TABLE notnull_tbl1 ALTER c1 DROP NOT NULL;
> 
> "ALTER TABLE notnull_tbl1 ALTER c0 DROP NOT NULL;"
> should fail?

No, this should not fail, and it is working correctly in master.  You
can drop the not-null constraint, but the column will still be
non-nullable, because the primary key still exists.  If you drop the
primary key later, then the column becomes nullable.  This is by design.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
"El miedo atento y previsor es la madre de la seguridad" (E. Burke)