Recreate primary key without dropping foreign keys?

Hi all,

In PostgreSQL 9.1.3, I have a few fairly large tables with bloated
primary key indexes.  I'm trying to replace them using newly created
unique indexes as outlined in the docs.  Something like:

CREATE UNIQUE INDEX CONCURRENTLY dist_id_temp_idx ON distributors (dist_id);
ALTER TABLE distributors DROP CONSTRAINT distributors_pkey,
    ADD CONSTRAINT distributors_pkey PRIMARY KEY USING INDEX
dist_id_temp_idx;

However, the initial drop of the primary key constraint fails because
there are a whole bunch of foreign keys depending on it.

I've done some searching and haven't found a workable solution.  Is
there any way to swap in the new index for the primary key constraint
without dropping all dependent foreign keys?  Or am I pretty much stuck
with dropping and recreating all of the foreign keys?

Thanks in advance.

Chris Ernst
Data Operations Engineer
Zvelo, Inc.
http://zvelo.com/