From: Tom Lane <tgl@sss.pgh.pa.us>
To: "David G. Johnston" <david.g.johnston@gmail.com>
cc: "elionescu@yahoo.com" <elionescu@yahoo.com>,
        "pgsql-docs@lists.postgresql.org" <pgsql-docs@lists.postgresql.org>
Subject: Re: incorrect (incomplete) description for "alter domain"
In-reply-to: <2585954.1722265086@sss.pgh.pa.us>
References: <172225092461.915373.6103973717483380183@wrigleys.postgresql.org>
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 <2585954.1722265086@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Mon, 29 Jul 2024 10:58:06 -0400"
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Date: Mon, 29 Jul 2024 11:17:41 -0400
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I wrote:
> I think the page is technically correct, but I'm inclined to duplicate
> this text from the CREATE DOMAIN page:

> 	where domain_constraint is:
> 	[ CONSTRAINT constraint_name ]
> 	{ NOT NULL | NULL | CHECK (expression) }

> rather than making readers go look that up.

Actually, there *is* a bug in the description, because experimentation
shows that CREATE DOMAIN accepts NULL in this syntax (as advertised)
but ALTER DOMAIN does not.  We could alternatively decide that that's
a code bug and make ALTER DOMAIN take it, but I don't think it's worth
any effort (and this behavior may actually have been intentional, too).
I think we should just add

	where domain_constraint is:

	[ CONSTRAINT constraint_name ]
	{ NOT NULL | CHECK (expression) }

to the ALTER DOMAIN page, and then remove the claim that it's
identical to CREATE DOMAIN.

			regards, tom lane