From: Ken Winter <ken@sunward.org>
To: 'PostgreSQL pg-sql list' <pgsql-sql@postgresql.org>
Subject: Variable column names in PL/pgSQL RECORD referencces
Date: Fri, 25 Nov 2005 13:01:40 -0500
Message-ID: <004901c5f1ea$4a322a10$6603a8c0@kenxp> (raw)
(Sorry for the redundancy - I sent this query earlier but forgot to put a
title on it. Seems like it would be more useful with a title, so here it is
again. If there's a moderator who can delete my earlier message, please do
so.)
In PL/pgSQL, is there a way to put a *variable* column-name in a dot
notation reference to a RECORD column?
For example, suppose I want to write a function like the following, which is
to be called by a "BEFORE INSERT" trigger:
CREATE OR REPLACE FUNCTION foo ( ) RETURNS TRIGGER AS
'
DECLARE
var VARCHAR;
BEGIN
var := TG_ARGV[0]
NEW.<the column whose name is the value of var> := ''whatever'';
RETURN NEW;
END;
'
LANGUAGE 'plpgsql'
;
The aim of this uninteresting function is to assign the value 'whatever' to
the table column that is passed in by the calling trigger as TG_ARGV[0],
i.e. the first calling argument.
What I don't know is what to put into the dot notation in place of ".<the
column whose name is the value of var>" so that the column of NEW that is
addressed by the assignment statement is the one passed in as the first
argument. Is there any PL/pgSQL construct that could be substituted in here
to achieve this result?
If not, can anybody suggest a way to write a trigger-called function that
would accomplish the same result?
In case it's not obvious, the underlying goal is to write a single
trigger-called function that could modify different columns for each trigger
that called it, where each trigger specified the target column by a calling
argument (or by any other viable mechanism).
~ TIA
~ Ken
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To: pgsql-sql@postgresql.org
Cc: ken@sunward.org
Subject: Re: Variable column names in PL/pgSQL RECORD referencces
In-Reply-To: <004901c5f1ea$4a322a10$6603a8c0@kenxp>
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