STRICT function returning a composite type - Mailing list pgsql-sql

I noted that such a function returns an empty rowset if a NULL value is
passed as an argument. Is it a bug or feature? I wish it was a feature,
because I probably want to use this behavour.

Here's an example:

CREATE TYPE ts_bounds AS (       sdate   timestamptz,       edate   timestamptz
);

CREATE OR REPLACE FUNCTION overlap_bounds(timestamptz, timestamptz, timestamptz, timestamptz)
RETURNS ts_bounds AS '
DECLARE       sdate1  ALIAS FOR $1;       edate1  ALIAS FOR $2;       sdate2  ALIAS FOR $3;       edate2  ALIAS FOR $4;
     res     ts_bounds%rowtype;
 
BEGIN       res.sdate := CASE WHEN sdate1 > sdate2 THEN sdate1 ELSE sdate2 END;       res.edate := CASE WHEN edate1 <
edate2THEN edate1 ELSE edate2 END;       IF res.sdate > res.edate THEN               res.sdate := NULL;
res.edate:= NULL;       END IF;       RETURN res;
 
END' LANGUAGE 'plPgSQL' STRICT;


fduch=# SELECT * from overlap_bounds('-infinity', 'today', 'yesterday', 'infinity');        sdate          |
edate
------------------------+------------------------2003-11-12 00:00:00+03 | 2003-11-13 00:00:00+03
(1 row)

fduch=# SELECT * from overlap_bounds('-infinity', 'today', 'yesterday', null);sdate | edate
-------+-------
(0 rows)


What I want is to get no rows if given intervals don't overlap instead of:
fduch=# SELECT * from overlap_bounds('-infinity', 'yesterday', 'today', 'infinity');sdate | edate
-------+-------      |
(1 row)

Is it possible without returning SETOF ts_bounds?


fduch=# SELECT version();                              version
---------------------------------------------------------------------PostgreSQL 7.3.4 on i386-portbld-freebsd4.8,
compiledby GCC 2.95.4
 


-- 
Fduch M. Pravking