From: Tom Lane <tgl@sss.pgh.pa.us>
To: Isaac Morland <isaac.morland@gmail.com>
cc: Robert Haas <robertmhaas@gmail.com>,
        Alvaro Herrera <alvherre@alvh.no-ip.org>,
        Pg Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: cataloguing NOT NULL constraints
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Comments: In-reply-to Isaac Morland <isaac.morland@gmail.com>
	message dated "Mon, 19 Sep 2022 09:54:41 -0400"
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Date: Mon, 19 Sep 2022 10:08:52 -0400
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Isaac Morland <isaac.morland@gmail.com> writes:
> I thought I saw some discussion about the SQL standard saying that there is
> a difference between putting NOT NULL in a column definition, and CHECK
> (column_name NOT NULL). So if we're going to take this seriously, I think
> that means there needs to be a field in pg_constraint which identifies
> whether a constraint is a "real" one created explicitly as a constraint, or
> if it is just one created because a field is marked NOT NULL.

If we're going to go that way, I think that we should take the further
step of making not-null constraints be their own contype rather than
an artificially generated CHECK.  The bloat in pg_constraint from CHECK
expressions made this way seems like an additional reason not to like
doing it like that.

			regards, tom lane