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Re: fail-safe sql update triggers

From: "Igor Neyman" <ineyman(at)perceptron(dot)com>
To: "Michael Monnerie" <michael(dot)monnerie(at)is(dot)it-management(dot)at>,<pgsql-admin(at)postgresql(dot)org>
Subject: Re: fail-safe sql update triggers
Date: 2010-09-07 12:55:27
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Lists: pgsql-admin
> -----Original Message-----
> From: Michael Monnerie [mailto:michael(dot)monnerie(at)is(dot)it-management(dot)at] 
> Sent: Friday, September 03, 2010 9:03 AM
> To: pgsql-admin(at)postgresql(dot)org
> Subject: fail-safe sql update triggers
> I want to log all activity from a table to a old_table. 
> Creating an ON INSERT trigger is simple, it just needs to
> INSERT INTO old_filter SELECT NEW.*;
> in a procedure that is called via the trigger. But what about 
> updates? There is no simple
> UPDATE old_filter SET NEW.* WHERE;
> so I would need to declare each column like
> UPDATE old_filter SET field1=NEW.field1,f2=NEW.f2,.... where 
> But that is error prone, because when the "filter" table is 
> changed to have a new column, the UPDATE statement would not 
> contain it. Is there a fail-proof shortcut?
> mit freundlichen Grüßen
> Michael Monnerie, Ing. BSc


You are seeing only half of the problem.
When you modify your "filter" table (i.e. add a column), not only UPDATE statement in your trigger function should be modified to reflect the change in the original "filter" table, but also your history table "old_filter" should be modified as well: new column should be added.

So, in short there is no "easy" way around.
When "source" table is modified, "destination" table and trigger function should be also modified.

Igor Neyman

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