Re: constraint modification on todo list

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Jeroen Ruigrok/asmodai" <asmodai(at)wxs(dot)nl>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: constraint modification on todo list
Date: 2003-09-08 20:41:42
Message-ID: 200309082041.h88KfgP27748@candle.pha.pa.us
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Tom Lane wrote:
> Jeroen Ruigrok/asmodai <asmodai(at)wxs(dot)nl> writes:
> > can someone add:
> > Add an ALTER TABLE MODIFY CONSTRAINT
> > item to the todo list?
>
> Why? For a constraint, it's not obvious what this would do for you that
> dropping and re-adding the constraint wouldn't do. In the places where
> we support CREATE OR REPLACE, it's because it's important to maintain
> continuity of the object's identity, but I don't see any need for that
> with respect to check constraints.

I assume MODIFY would allow you to alter the constraint without
re-checking all the rows, as would be required by DROP/ADD. However, if
you are modifying the constraint, wouldn't we have to recheck all the
rows anyway. Of course, one idea would be to allow MODIFY to make
changes that _don't_ require rechecking, but I have no idea what such
changes would be.

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