very slow execution of stored procedures

Greetings,

    I found something very weird related with stored procedures execution. I
have this stored procedure to finalize a phone call, writing tha time of
call finalization and some other values to a calls table, called
cham_chamada. Please check this out (very simple) :

------------------------------------------------------------------

CREATE FUNCTION finaliza_chamv2(INT4, INT4, INT4, CHAR(23), CHAR(23),
CHAR(1),
                                INT4, INT4, INT4, CHAR(23), INT4, INT4,
CHAR(25),
                                INT4, INT4, INT4) RETURNS int4 AS
'
DECLARE
  pbxs           ALIAS FOR $1;
  pchave         ALIAS FOR $2;
  pidentificacao ALIAS FOR $3;
  pdtinicial     ALIAS FOR $4;
  pdtfinal       ALIAS FOR $5;
  pflgliber      ALIAS FOR $6;
  ptempototal    ALIAS FOR $7;
  pcodliber      ALIAS FOR $8;
  pddd           ALIAS FOR $9;
  pdtocup        ALIAS FOR $10;
  pindicadora    ALIAS FOR $11;
  pcategoria     ALIAS FOR $12;
  pidentidadea   ALIAS FOR $13;
  pfds           ALIAS FOR $14;
  presultcham    ALIAS FOR $15;
  pcifraorigem   ALIAS FOR $16;

BEGIN

  UPDATE cham_chamada
  SET dt_final        = TIMESTAMP(pdtfinal),
      flg_liberacao   = pflgliber,
      temp_total      = ptempototal,
      cod_liberjuntor = pcodliber,
      ddd             = pddd,
      indicadora      = pindicadora,
      cod_categoria   = pcategoria,
      identidadea     = pidentidadea,
      cod_fds         = pfds,
      cod_resultcham  = presultcham,
      cifra_origem    = pcifraorigem
  WHERE cod_bxs       = pbxs           AND
        chave         = pchave         AND
        identificacao = pidentificacao AND
        dt_inicial    = TIMESTAMP(pdtinicial);

  IF pdtocup <> '''' THEN
    UPDATE cham_servico
    SET
      dt_ocupacao = TIMESTAMP(pdtocup)
    WHERE
      cod_bxs       = pbxs           AND
      chave         = pchave         AND
      identificacao = pidentificacao AND
      dt_inicial    = TIMESTAMP(pdtinicial)     AND
      dt_finalizacao is null;
  END IF;

  RETURN 0;

END;
'
LANGUAGE 'plpgsql';

------------------------------------------------------------------

Once you know all about this stored procedure, lets see this call :
SELECT finaliza_chamv2(1,65535,49644,'2001-04-17 11:50:55','2001-04-17
12:17:40', '0', 0, 0, 48, '', 0, 10, '2817107', 0, 261, 65535);

If I change all variables to the parameters value inside the stored
procedure and then execute the frist script, then it is very fast, check out
:


bxs=#
bxs=# UPDATE cham_chamada
bxs-#   SET dt_final = TIMESTAMP('2001-04-17 12:12:10'),
bxs-#       flg_liberacao = '0',
bxs-#       temp_total = 0,
bxs-#       cod_liberjuntor = 0,
bxs-#       ddd = 48,
bxs-#       indicadora = 0,
bxs-#       cod_categoria = 10,
bxs-#       identidadea = '2817005',
bxs-#       cod_fds = 0,
bxs-#       cod_resultcham  = 6,
bxs-#       cifra_origem = 65535
bxs-#   WHERE cod_bxs = 1 AND
bxs-#         chave = 65535 AND
bxs-#         identificacao = 49644 AND
bxs-#         dt_inicial = TIMESTAMP('2001-04-17 12:12:00');
UPDATE 1

execution time : <1ms


now its time to do the same thing using the stored procedure :
bxs=#
bxs=# SELECT finaliza_chamv2(1,65535,49644,'2001-04-17 11:50:55','2001-04-17
12:17:40', '0', 0, 0, 48, '', 0, 10, '2817107', 0, 261, 65535);
 finaliza_chamv2
-----------------
               0
(1 row)

execution time : about 5s

Is it supose to execute with different speed? What can I do to fix it?

I'm using postgres RPM 7.0.3-2 in RedHat 6.2.

ps: There are some specific procedures I needed to execute before I got
pl/pgsql working :

CREATE FUNCTION plpgsql_call_handler ()
RETURNS opaque AS '/usr/lib/pgsql/plpgsql.so'
LANGUAGE 'C';

CREATE PROCEDURAL LANGUAGE 'plpgsql'
HANDLER plpgsql_call_handler
LANCOMPILER 'PL/PgSql internal';


Best regards from Brazil,

José Vilson de Mello de Farias
Dígitro Tecnologia Ltda - Brasil