Date: Thu, 16 Jan 2003 20:43:49 -0800 (PST)
From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Matthew Nuzum <cobalt@bearfruit.org>
Cc: <pgsql-sql@postgresql.org>
Subject: Re: cannot create function that uses variable table name
In-Reply-To: <001d01c2bdd9$191b07f0$6700a8c0@mattspc>
Message-ID: <20030116204152.I15804-100000@megazone23.bigpanda.com>
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On Thu, 16 Jan 2003, Matthew Nuzum wrote:

> I have a number of tables in my database that use the concept of
> =93display order=94, which is a field that can be used in an order by cla=
use
> to dictate what order the results should come out in.
> =A0
> I thought I would be crafty and devise a function that would always
> return the highest numbered item in the table.  But it doesn=92t work.  It
> always gives me a parse error at $1.  Here=92s the function:
>
> CREATE OR REPLACE FUNCTION get_last_dsply_order(
>    varchar,            -- tablename
>    varchar,            -- id_col_name
>    varchar)            -- where_item
>    RETURNS integer AS '
>    DECLARE total_items integer;
>       tablename ALIAS FOR $1;
>       id_col_name ALIAS FOR $2;
>       where_item ALIAS FOR $3;
>    BEGIN
>       SELECT INTO total_items count(*) FROM tablename WHERE id_col_name
> =3D where_item;
>    RETURN total_items;
> END;
> ' LANGUAGE 'plpgsql';

You'll need to look into EXECUTE. You also are going to have to
watch out for concurrency issues since two transactions calling
this function at the same time for the same args are likely to
give incorrect results.