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Tantalizing reference to passing data from NEW variable in a trigger function...

From: Rich Cullingford <rculling(at)sysd(dot)com>
To: pgsql-interfaces(at)postgresql(dot)org
Subject: Tantalizing reference to passing data from NEW variable in a trigger function...
Date: 2004-04-26 15:38:13
Message-ID: 408D2CE5.1090108@sysd.com (view raw or flat)
Thread:
Lists: pgsql-interfaces
All,
This question seems to have been asked a number of times on this list, 
recently (including by me) without being answered: how to pass the row 
data stored in the NEW variable from a trigger function into a 
sub-function. None of the obvious syntaxes work, including one by a 
respondent in this list that suggested assigning NEW to a record 
variable, and then passing *that*. After searching up and down the 
archives, I see the following tantalizing snippet (from 6/2003) in the 
context of a rule:

Gunter Diehl <gdid ( at ) gmx ( dot ) de> writes:
 > create funtion f1(v, v) returns void as '...'
 > create rule vupt as on update to v do instead select f1(new, old)
 > While accepting this definitions, pg says it can not handle "whole-tuple
 > references" at runtime.

FWIW, the "old" case works fine.  "new" doesn't work so well because the
new row hasn't been formed into a tuple at the point where the rule
runs; it only exists as a list of variables.  (This is a rather handwavy
explanation, but I think it captures the key point.)  While this could
probably be fixed with some effort, I doubt it's going to happen soon.
Is there any chance of doing what you want with a trigger instead of a
rule?

                                                     ^^^^^

If there's a page somewhere that says how to do this, I'd be extremely 
grateful for a pointer. The obvious maneuver of copying NEW's data 
field-by-field into a composite variable is rather unappetizing when the 
row is wide...
                           Rich Cullingford
                           rculling(at)sysd(dot)com


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Next:From: Joe ConwayDate: 2004-04-26 17:05:07
Subject: Re: Tantalizing reference to passing data from NEW variable
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Subject: Re: I hope I'm missing something...

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