ERROR: duplicate key violates unique constraint - Mailing list pgsql-sql

Need help on this problem. I've created two functions. The function 
should perform a few sql processes. The problem is I got different 
results when I call the function and when I manually run the sql command.

I'm using postgresql 7.4.2.

The two functions involved are
CREATE TABLE sensor_signature ( sid             INTEGER,                               rh_sign_id      INTEGER,
                     PRIMARY KEY (sid,rh_sign_id));
 

CREATE TABLE rule_header ( rh_sign_id   INTEGER,                          rh_status    INTEGER,
rh_action    VARCHAR(6),                          proto        VARCHAR(10),                          source_ip
VARCHAR(255),                         source_port  VARCHAR(64),                          dest_ip      VARCHAR(255),
                    dest_port    VARCHAR(64),                          dir_operator VARCHAR(64),
 category     VARCHAR(64),                          rh_revision  INTEGER,                          timestamp
timestamp,                         rh_ord       INTEGER,                          PRIMARY KEY (rh_sign_id));
 

And my functions are

CREATE OR REPLACE FUNCTION update_sen_sig (integer, varchar)
RETURNS integer AS '
DECLARE   sign_id alias FOR $1;   category alias FOR $2;   temp_sid integer;   temp_category varchar;   T1Cursor
refcursor;
BEGIN   select * into temp_category from get_root_path(category);   OPEN T1Cursor FOR      SELECT sid FROM
conf_categoryWHERE          category_name like temp_category and category_status=1;     LOOP      FETCH T1Cursor INTO
temp_sid;     EXIT WHEN NOT FOUND;      INSERT INTO sensor_signature VALUES (temp_sid, sign_id);      RAISE NOTICE ''
INSERTINTO sensor_signature VALUES % % '', 
 
temp_sid,sign_id;   END LOOP;   CLOSE T1Cursor;
--- COMMIT;
RETURN 0;
END;
' LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION rule_header_add 
(integer,integer,varchar,varchar,varchar,varchar,varchar,varchar,varchar,varchar,integer,integer) 

RETURNS integer AS '
DECLARE   var_f0 alias FOR $1;    -- rh_sign_id   var_f1 alias FOR $2;    -- rh_status   var_f2 alias FOR $3;    --
rh_action  var_f3 alias FOR $4;    -- proto   var_f4 alias FOR $5;    -- source_ip   var_f5 alias FOR $6;    --
source_port  var_f6 alias FOR $7;    -- dest_ip   var_f7 alias FOR $8;    -- dest_port   var_f8 alias FOR $9;    --
dir_operator  var_f9 alias FOR $10;    -- category   var_f10 alias FOR $11;    -- rh_revision   var_f11 alias FOR $12;
 -- rh_ord   curtime timestamp;   var_temp_RH_ORD integer;
 
BEGIN   curtime := current_timestamp;   SELECT rh_ord INTO var_temp_RH_ORD FROM rule_header      WHERE rh_sign_id =
var_f0;  IF NOT FOUND THEN      INSERT INTO rule_header       VALUES 
 
(var_f0,var_f1,var_f2,var_f3,var_f4,var_f5,var_f6,var_f7,var_f8,var_f9,var_f10,curtime,var_f11);
      RAISE NOTICE '' INSERT INTO rule_header VALUES % % % % % % % % % 
% % % '', 
var_f0,var_f1,var_f2,var_f3,var_f4,var_f5,var_f6,var_f7,var_f8,var_f9,var_f10,curtime,var_f11;
---        select update_sen_sig(var_f0,var_f9);      perform update_sen_sig(var_f0,var_f9);         RETURN 0;   ELSE
  UPDATE rule_header SET rh_status=var_f1, rh_action=var_f2, 
 
proto=var_f3,source_ip=var_f4, source_port=var_f5, dest_ip=var_f6, 
dest_port=var_f7, dir_operator=var_f8, category=var_f9, 
rh_revision=var_f10, timestamp=curtime, rh_ord=var_temp_RH_ORD where 
rh_sign_id=var_f0;           DELETE FROM rule_option where rh_sign_id=var_f0;       RETURN 1;   END IF;
END;
' LANGUAGE 'plpgsql';

Issue is
cews=> select
rule_header_add(999,1,'alert','ip','$EXTERNAL_NET','any','$HOME_NET','any','->','dos.rules',3,0);
NOTICE:   INSERT INTO rule_header VALUES 999 1 alert ip $EXTERNAL_NET any
$HOME_NET any -> dos.rules 3 2004-06-04 15:21:30.448633
NOTICE:   INSERT INTO sensor_signature VALUES -1 999
CONTEXT:  PL/pgSQL function "rule_header_add" line 26 at perform
ERROR:  duplicate key violates unique constraint "sensor_signature_pkey"
CONTEXT:  PL/pgSQL function "update_sen_sig" line 16 at SQL statement
PL/pgSQL function "rule_header_add" line 26 at perform

I thought it might be caused by duplicated data. But ...
cews=> insert into rule_header values
(268,1,'alert','ip','$EXTERNAL_NET','any','$HOME_NET','any','->','dos.rules',3,current_timestamp,0);
INSERT 29393 1

And
cews=> insert into sensor_signature values (-1,268);
INSERT 29394 1

That commands work perfectly. Could somebody tell me why and how to 
solve this. Thanks.

Azmi