Re: Statement triggers 7.4 NEW/OLD

From: Andreas Pflug <Andreas(dot)Pflug(at)web(dot)de>
To: Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-sql(at)postgresql(dot)org
Subject: Re: Statement triggers 7.4 NEW/OLD
Date: 2003-04-26 08:50:06
Message-ID: 3EAA483E.2060204@web.de
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Josh Berkus wrote:

>>IMHO statement triggers instead should have access to the NEW and OLD
>>rows through some mechanism. I can think of NEW and OLD being reference
>>cursors in the case of statement triggers, and the trigger then can
>>FETCH the rows from there.
>>
>>
>
>Yeah; how else could it possibly work?
>
>
>
Why do it easy if you can have it difficult? ;-) If I want to perform
row by row actions I use a row level trigger!
Statement triggers need to work like this:
Instead of
NEW.foo := 1;
you code
UPDATE NEW SET foo=1;
If the statement trigger doesn't offer a complete SETOF RECORD, It's
pretty useless.
In my case, updates and deletes on a table could possibly touch
thousands of rows at the same time, and the trigger will update
aggregated values in another table, and insert or delete a third one
with 3-4 additional statements. This is pretty fast if implemented as
true statement trigger, but will possibly blow the system if done row by
row. Imagine a single statement, that triggers ROW_COUNT*4 statements,
where ROW_COUNT can easily be 1000, 10000 or much more!

Regards,
Andreas

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