varchar as primary key

[Matthew Hixson <hixson@xxxxxxxxxxxxxxxx>]

I'm investigating the usage of a UUID primary key generator using  
Hibernate and Postgres.  The reason for using a UUID is that we will  
have an application hosted at different sites in different  
databases.  We will need to aggregate the data back into a single  
database from time to time and we want to avoid PK collisions.
  Is there a significant performance difference between using int  
primary keys and string primary keys in Postgres?
  Thanks,
   -M@