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From: "Ken Winter" <ken@sunward.org>
To: "PostgreSQL pg-sql list" <pgsql-sql@postgresql.org>
Subject: 
Date: Wed, 23 Nov 2005 23:23:05 -0500
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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=20
    '
    DECLARE=20
        var VARCHAR;
    BEGIN
        var :=3D TG_ARGV[0]      =20
        NEW.<the column whose name is the value of var> :=3D =
''whatever'';
        RETURN NEW;    =20
    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. =20

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