slow update

Hi all;

I have a query that does this:

update tab_x set (inactive_dt, last_update_dt) =
((select run_dt from current_run_date), (select run_dt from
current_run_date))
where
cust_id::text || loc_id::text in
(select cust_id::text || loc_id::text from summary_tab);


The current_run_date table has only 1 row in it
the summary_tab table has 0 rows and the tab_x had 450,000 rows

The update takes 45min even though there is no rows to update.
I have a compound index (cust_id, loc_id) on both tables (summary_tab
and tab_x)

How can I speed this up ?


Thanks in advance for any thoughts, suggestions, etc...


/Kevin