Message-ID: <7d0f1fea-0f1a-2c9f-9b02-867b73abee78@gmail.com>
Date: Fri, 3 May 2024 07:00:00 +0300
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Subject: Re: cataloguing NOT NULL constraints
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To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Dean Rasheed <dean.a.rasheed@gmail.com>,
 Andrew Bille <andrewbille@gmail.com>, Peter Eisentraut
 <peter@eisentraut.org>, Robert Haas <robertmhaas@gmail.com>,
 pgsql-hackers@lists.postgresql.org
References: <202405021621.ftmuhmfg7f2j@alvherre.pgsql>
From: Alexander Lakhin <exclusion@gmail.com>
In-Reply-To: <202405021621.ftmuhmfg7f2j@alvherre.pgsql>
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02.05.2024 19:21, Alvaro Herrera wrote:

> Now, you could claim that the standard doesn't mention
> INCLUDING/EXCLUDING CONSTRAINTS, therefore since we have come up with
> its definition then we should make it affect not-null constraints.
> However, there's also this note:
>
>    NOTE 520 — <column constraint>s, except for NOT NULL, are not included in
>    CDi; <column constraint definition>s are effectively transformed to <table
>    constraint definition>s and are thereby also excluded.
>
> which is explicitly saying that not-null constraints are treated
> differently; in essence, with INCLUDING CONSTRAINTS we choose to affect
> the constraints that the standard says to ignore.

Thank you for very detailed and convincing explanation!

Now I see what the last sentence here (from [1]) means:
INCLUDING CONSTRAINTS

     CHECK constraints will be copied. No distinction is made between
     column constraints and table constraints. _Not-null constraints are
     always copied to the new table._

(I hadn't paid enough attention to it, because this exact paragraph is
also presented in previous versions...)

[1] https://www.postgresql.org/docs/devel/sql-createtable.html

Best regards,
Alexander