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Dynamic access to record columns (in PL/pgsql)

From: Daniele Mazzini <daniele(dot)mazzini(at)libero(dot)it>
To: pgsql-general(at)postgresql(dot)org
Subject: Dynamic access to record columns (in PL/pgsql)
Date: 2006-09-30 10:51:07
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-general

I have a trigger procedure which I want to be called after insert or 
update on different tables. In this procedure, I need to find the values 
of key fields for the affected table in the NEW record, but I can't find 
a way to access a field the name of which I only know at execution time. 
I tried many workarounds, for example this:

fieldname := name of key field;
EXECUTE 'SELECT NEW.'||fieldname INTO fieldvalue;

But none of them worked. I found a one-year-old thread about this kind 
of dynamic access, which proposed a syntax like this: NEW.(fieldname), 
but this hasn't be implemented in the current version and, apparently, 
no different methods where suggested. Can anybody suggest me how to do 
that? Right now I can only think of programmatically generating one 
different procedure for every table I want to track (there are 42), but 
this would be very clunky solution.

Thanks for your time

Daniele Mazzini


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