A tale of two similar databases

Hi All,

I am using PostgreSQL 7.3.2 on a server running Red Hat Linux 9.0.

I have two databases ( identical schema and similar data ).

One database, D1 contains the actual data of a Production Application.
The other D2 contains dummy data which is used during development and
testing of the application.

D2 actually contains a recent snapshot of D1 and hence contain almost
the same data.

The strange thing is that D1 is extremely fast whereas D2 is relatively
slow for any given query.
(Thank God, it isnt the other way round :) )

Eg,
An extensive Statistics query returns in a matter of seconds on D1 but
takes close to a minute on D2

I would like to know if anybody can answer why it is so.

Thanks in advance
- Kishore