CREATE TABLE audit (
audit_id serial not null primary key,
create_date timestamp,
create_user_id int references users(user_id),
create_ip inet, 
create_server int,
.....
);

create table test(
test_id not null primary key,
audit_id references audit(audit_id),
.....
);

CREATE TABLE audit (
audit_id serial not null primary key,
create_date timestamp,
create_user_id int references users(user_id),
create_ip inet, 
update_server int,
update_date timestamp,
update_user_id int references users(user_id),
update_ip inet, 
update_server int
);

create table test(
test_id serial not null primary key,
a text
);

create table au_test(
test_id int,
a text
);

CREATE TABLE audit (
audit_id serial not null primary key,
table_oid oid,
oper char(1),
mod_user varchar(50),
mod_date timestamp
);

create or replace function tf_audit() returns trigger 
as
$$
declare 
  sql text;
begin
  if TG_OP='INSERT' then
    insert into audit(table_oid, oper, mod_user, mod_date) 
    select TG_RELID, 'i', current_user, now();

  elseif TG_OP='UPDATE' then
    insert into audit(table_oid, oper, mod_user, mod_date) 
    select TG_RELID, 'u', current_user, now();

   execute 'insert into au_'||TG_TABLE_NAME||' select $1.*' USING  old;  
     
  elseif TG_OP='DELETE' then
    insert into audit(table_oid, oper, mod_user, mod_date) 
    select TG_RELID, 'd', current_user, now();

    execute 'insert into au_'||TG_TABLE_NAME||' select $1.*' USING  old; 
 
  end if; 

  if TG_OP='DELETE' then
    return old;
  else 
    return new;
  end if;    
end;
$$
language 'plpgsql';

CREATE TRIGGER trg_test
  BEFORE INSERT OR UPDATE OR DELETE
  ON test
  FOR EACH ROW
  EXECUTE PROCEDURE tf_audit();

insert into test (a) values ('aaa');
update test set a='bbb' where test_id=1;
delete from test where test_id=1;
select * from audit;
--select * from au_test;