BUG #4559: performance issue

The following bug has been logged online:

Bug reference:      4559
Logged by:          M. Alaa ElGohary
Email address:      alaa.elgohary@backandfront.ws
PostgreSQL version: 7.4.19
Operating system:   FreeBSD 6.3
Description:        performance issue
Details:

I have a POS application that performs end of day process in which data is
transfered from a set of tables to another this process stops completely
with no reason when i make a dump of the database and drop then create and
restore the dump the end of day process performs extremely fast with no
stopage
i need to know whats the reason that stops this process and why is it
overcome when i drop and restore the database and how can i solve this
without needing to drop and restore the database
thanks