update - which way quicker?

[Emi Lu <emilu@xxxxxxxxxxxxxxxxx>]

Good morning,

Tried to compare Table1 based on Table2

. update table1.col = false
  if table1.pk_cols not in table2.pk_cols



For the following two ways, (2) always performs better than (1) right,
and I need your inputs.
========================================================================
(1) update table1
    set col = false
    where table1.pk_co1 || table1.pk_col2.... || table1.pk_colN

    NOT IN

    (select pk_co1 || pk_col2.... || pk_colN
     from table2
     )

(2) ResultSet(rs) =
    select pk_col1||pk_col2... || pk_colN
    from table1
    left join table2 using (pk_col1..., pk_colN)
    where table2.pk_col1 is null

    Then for each rs record, do:
    update table1
    set col = false
    where col1||... colN in rs.value

Thanks a lot!