Sam,
> I'd like to get some opinions if there are any benefits (i.e. in
> terms of performance) of creating two separate databases, one for
> transactions (insert, update, delete) and the other one is for
> retrieval/search (select).
No. Not in Postgresql, unless you wanted to get really exotic. Also,
keep in mind that you cannot join tables from seperate databases in
postgresql.
There are *lots* of performance advantages to be had by managing disk
access and memory carefully. But not through seperate databases.
-Josh Berkus