Less rows -> better performance?

Dear PostgreSQL community,

first some info about our application:

- Online course directory for a University
- Amount of data: complete dump is 27 MB
- Semester is part of primary key in each table
- Data for approx. 10 semesters stored in the DB
- Read-only access from web application (JDBC)

Our client has asked us if the performance of the application could be
improved by moving the data from previous years to a separate "archive"
application. This would reduce the overall amount of data in the main
application by about 80% at the moment.

Actually I doubt that this will have the desired effect, since the
semester is part of the primary key in virtually all tables (apart from
some small tables containing string constants etc.), and therefore
indexed. Some tests with EXPLAIN ANALYZE and some web tests (JMeter)
seem to confirm this, the queries showed the same performance with 2 and
10 semesters.

But since I'm not sure yet, I would very much appreciate any answers to
the following questions:

- Do you think the approach (reducing the data) is effective?
- Are there any particular tests which I should do?

Thanks a lot in advance!

-- Andreas

--
Andreas Hartmann, CTO
BeCompany GmbH
http://www.becompany.ch
Tel.: +41 (0) 43 818 57 01