From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Hills <mark@xwax.org>
cc: Laurenz Albe <laurenz.albe@cybertec.at>,
        pgsql-performance@lists.postgresql.org
Subject: Re: Domain check taking place unnecessarily?
In-reply-to: <2302091035450.14632@stax.localdomain>
References: <2302081605290.5352@stax.localdomain>
 <4b1a0c9e36280b1d4abeb4fb6336832409df6ae0.camel@cybertec.at>
 <2302091035450.14632@stax.localdomain>
Comments: In-reply-to Mark Hills <mark@xwax.org>
	message dated "Thu, 09 Feb 2023 10:56:35 +0000"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <3893889.1675955401.1@sss.pgh.pa.us>
Date: Thu, 09 Feb 2023 10:10:01 -0500
Message-ID: <3893890.1675955401@sss.pgh.pa.us>
Archived-At: 
 <https://www.postgresql.org/message-id/3893890.1675955401%40sss.pgh.pa.us>
Precedence: bulk

Mark Hills <mark@xwax.org> writes:
> On Wed, 8 Feb 2023, Laurenz Albe wrote:
>> It takes 30 seconds to schan the table and determine that all existing 
>> rows satisky the constraint.

> But there's no existing data (note this is adding column, not constraint)

> Existing rows are guaranteed to satisfy the domain check, because the 
> domain check is guaranteed to be immutable (per [1] in my original mail)

immutable != "will accept null".

There could be some more optimizations here, perhaps, but there aren't.

			regards, tom lane