From: Michael Fuhr <mike@fuhr.org>
To: Kashmira Patel (kupatel) <kupatel@cisco.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Question about check constraints
Date: Fri, 27 Jan 2006 17:40:22 -0700
Message-ID: <20060128004022.GA20476@winnie.fuhr.org> (raw)
In-Reply-To: <18AE59788A3FC640A367E5652E664D8001731288@xmb-sjc-237.amer.cisco.com>
References: <18AE59788A3FC640A367E5652E664D8001731288@xmb-sjc-237.amer.cisco.com>
On Fri, Jan 27, 2006 at 03:06:26PM -0800, Kashmira Patel (kupatel) wrote:
> I have a table where two columns have two different check constraints
> associated with them. When I update one column, the check constraint on
> the other column is also executed. Is there a way to avoid this? I want
> to check only for the condition defined for the column being updated.
I don't think you can change this behavior: each CHECK constraint
is evaluated for the new row regardless of whether a particular
column changed or not. However, you could enforce the constraints
with a trigger and skip checks where NEW.column is the same as
OLD.column.
Why the concern? Are the checks expensive? Do they have side
effects? What do they do?
--
Michael Fuhr
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To: pgsql-sql@postgresql.org
Cc: mike@fuhr.org, kupatel@cisco.com
Subject: Re: Question about check constraints
In-Reply-To: <20060128004022.GA20476@winnie.fuhr.org>
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