In default Openerp all the table "id"  column created with Primary key auto increment using ORM.

orm.py code

    def _create_table(self, cr):
        cr.execute('CREATE TABLE "%s" (id SERIAL NOT NULL, PRIMARY KEY(id))' % (self._table,))
        cr.execute(("COMMENT ON TABLE \"%s\" IS %%s" % self._table), (self._description,))
        _schema.debug("Table '%s': created", self._table)

 if self._log_access:
            upd0 += ',create_uid,create_date,write_uid,write_date'
            upd1 += ",%s,(now() at time zone 'UTC'),%s,(now() at time zone 'UTC')"
            upd2.extend((user, user))
        cr.execute('insert into "'+self._table+'" (id'+upd0+") values ("+str(id_new)+upd1+')', tuple(upd2))