From: Gerardo Herzig <gherzig@fmed.uba.ar>
To: pgsql-sql@postgresql.org
Subject: Re: statement-level trigger sample out there?
Date: Thu, 29 Nov 2007 16:18:02 -0300
Message-ID: <474F106A.5080107@fmed.uba.ar> (raw)
In-Reply-To: <474EC9CE.9090609@gmail.com>
References: <20071129130159.110470@gmx.net>
<162867790711290548t2a050d59ta77595c2b05d59ce@mail.gmail.com>
<474EC9CE.9090609@gmail.com>
Stephen Cook wrote:
> I am curious (coming from a MS SQL Server background, I just started
> playing with PostgreSQL recently).
>
> What type of situation would warrant a statement-level trigger that
> can't access the old and new values? Without that access, isn't the
> only information you get is the fact that an operation occurred on the
> table? Or am I missing something?
>
> -- Stephen
What about this. Suppose you have this table "planets":
planet_name | star_id|....
There is a lot of stars, right? And if a very common query involves a
"select planet_name, count(*) from planets group by star_id"....Well, if
there is 1.000.000.000 of galaxies, and 1.000.000.000.000 of stars per
galaxy...Thats a lot of planets to count!!! So maybe you want a helper
table who maintains such of subtotals.
Well, each time you discover a new galaxy, insert every planet in the
monster table, and *after* all the inserts, run a trigger for updating
the helper table.
Cheers.
Gerardo
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Subject: Re: statement-level trigger sample out there?
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