update one table with another

Hello,

I am looking for a way to update one table with another. I tried the
following schema to update table2 based on data in table1. The idea is that
I have a slowly changing dimension and I need to update data in the
dimension based on an updated version of the table. I don't want to have to
drop my foreign key constraints, delete all the data, copy new data, and
then re-establish the constraints.

The schema (taken from forums.devshed.com)

update table2
set link = t1.link
from table2 t2 inner join table1 t1 on t2.name = t1.name

Applying to my own situation:

update entities
set customer_status = t1.customer_status
from entities t2 inner join entity_dimension_update t1 on t2.entity_id =
t1.entity_id

(where entitiy_id is my primary key and customer_status is a varchar(11) and
entity_dimension_update is a structural copy of entities)

I'm not sure I entirely follow the logic here. I understand that the table
being updated is somehow joined with the table in the from clause. I suppose
that by including table2 itself as part of a joined table in the from
clause, something like a join between the updated table and the updating
table is accomplished (joined on a key to ensure a unique update value).

The query ran for half an hour before I cancelled it.

I am using Postgres 8.3. The only constraint on either table is the primary
key constraint on entity_id. Each table has 62960 rows.

Is there something I can do to speed this process up?

Thank you,
Matt

--
matthew(dot)pugsley(at)gmail(dot)com