From: | Florian Pflug <fgp(at)phlo(dot)org> |
---|---|
To: | Noah Misch <noah(at)2ndQuadrant(dot)com> |
Cc: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: augmenting MultiXacts to improve foreign keys |
Date: | 2011-08-10 08:15:49 |
Message-ID: | 562B5BB5-DA06-4CD6-881B-A99D1EEC8CA6@phlo.org |
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Lists: | pgsql-hackers |
On Aug10, 2011, at 08:45 , Noah Misch wrote:
> On Tue, Aug 09, 2011 at 09:41:00PM +0200, Florian Pflug wrote:
>> Couldn't we simply give the user a way to specify, per column, whether or
>> not that column is a "KEY" column? Creating a foreign key constraint could
>> still implicitly mark all referenced columns as KEY columns, but columns
>> would no longer be "KEY" columns simply because they're part of a UNIQUE
>> constraint. Users would be free to add arbitrary columns to the set of
>> "KEY" columns by doing ALTER TABLE ALTER COLUMN SET KEY.
>
> What would be the use case for manually expanding the set of key columns?
You'd use that if you implemented a FK-like constraint (e.g. a FK on an
array-values field). Without a way to manually expand the set of KEY columns,
such a non-core FK constraint couldn't use the lighter locks.
best regards,
Florian Pflug
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