CREATE OR REPLACE FUNCTION commodities_check()
  RETURNS "trigger" AS
$$
declare
begin
  raise notice '%', new.id_com;
  return new;
end;
$$
  LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION commodities_check() RETURNS trigger AS
$body$
begin
  raise notice '%', new.id_com;
  return new;
end;
$body$
LANGUAGE 'plpgsql';

--DROP TABLE comdeal;
--DROP FUNCTION commodities_check();

CREATE TABLE comdeal( 
id_com INTEGER, 
id_deal INTEGER, 
quantity INTEGER);

CREATE FUNCTION commodities_check() RETURNS trigger AS
$body$
begin
  raise notice '%', new.id_com;
  return new;
end;
$body$
LANGUAGE 'plpgsql';

CREATE TRIGGER "B_IU_commodities_check" BEFORE INSERT OR UPDATE ON comdeal 
FOR EACH ROW EXECUTE PROCEDURE commodities_check();

INSERT INTO comdeal VALUES ( 1 ,  1 ,  2 );

NOTICE:   1