From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Garamond <davidgaramond@gmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: autoupdating mtime column
Date: Fri, 04 Aug 2006 12:10:23 -0400
Message-ID: <29505.1154707823@sss.pgh.pa.us> (raw)
In-Reply-To: <7c33d060608040811s6dcaa3abia137188076a76781@mail.gmail.com>
References: <7c33d060608040516n799af906sf74e1c645a47caff@mail.gmail.com>
<44D34242.6000901@archonet.com>
<7c33d060608040811s6dcaa3abia137188076a76781@mail.gmail.com>
"David Garamond" <davidgaramond@gmail.com> writes:
> On 8/4/06, Richard Huxton <dev@archonet.com> wrote:
>> Just check for OLD.mtime = NEW.mtime, or am I missing something here?
> How do I differentiate between:
> UPDATE t SET mtime=mtime ...;
> in which mtime is specifically set and should not change,
You don't. A trigger has no way to know the history of the row it's
looking at --- consider the possibility that it was already modified
by earlier triggers.
If you are really intent on having a way to suppress the mtime update
you could dedicate an additional field to the purpose, eg
UPDATE t SET foo=..., bar=..., keepmtime = true ...
and in the trigger something like
if new.keepmtime then
new.keepmtime = false;
else
new.mtime = now();
As long as nothing else ever touches keepmtime this would work.
Personally I'm dubious that it's worth the trouble --- do you
have a real use-case for suppressing mtime updates?
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, davidgaramond@gmail.com
Subject: Re: autoupdating mtime column
In-Reply-To: <29505.1154707823@sss.pgh.pa.us>
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