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Date: Tue, 26 Nov 2002 12:55:36 +0100
From: Christoph Haller <ch@rodos.fzk.de>
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To: nonsolosoft@diff.org
Cc: pgsql-sql@postgresql.org
Subject: Re: PL/SQL trouble
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> I really don't understand following PostgreSQL 7.2.3 behaviour:
>
> $ psql mydb
> mydb=> CREATE FUNCTION MONDAY(timestamp) RETURNS DATE AS '
>  DECLARE
>   var1 date;
>  BEGIN
>   select into var1 to_date($1::date-(case when extract(DOW from
> timestamp $1) = 0 then 6 else (extract(DOW from timestamp $1)-1)
end));
>   RETURN var1;
>  END'
> language 'plpgsql';
>
> CREATE
> mydb=> select MONDAY('now'::timestamp);
> NOTICE:  Error occurred while executing PL/pgSQL function MONDAY
> NOTICE:  line 4 at select into variables
> ERROR:  parser: parse error at or near "$2"
> mydb=> \q
>
> But I've not inserted any $2 there.
> I've rewritten the same function in other ways but I've got the same
error.
>

Something like the following works (as Richard already pointed out):
CREATE OR REPLACE FUNCTION MONDAY(timestamp) RETURNS DATE AS '
 DECLARE
  ts_param    ALIAS FOR $1;
  var1 date;
 BEGIN
  select into var1 to_date(ts_param::date-
  (case when extract(DOW from ts_param) = 0
  then 6 else (extract(DOW from ts_param)-1) end),''DD'');
  RETURN var1;
 END'
language 'plpgsql';

Me personally would prefer another approach:
CREATE OR REPLACE FUNCTION MONDAY(timestamp) RETURNS DATE AS '
 DECLARE
  ts_param    ALIAS FOR $1;
  var1 date;
  var2 double precision;
 BEGIN
  var2 := extract(DOW from ts_param);
  IF var2 = 0 THEN
   var2 := 6;
  ELSE
   var2 := var2 - 1;
  END IF;
  var1 := to_date(ts_param::date - var2,''DD'');
 RETURN var1;
 END'
language 'plpgsql';
because it's easier to read, but that's only a matter of taste I
suppose.

Regards, Christoph