BUG #8246: Delete Cascade causing performance issues

The following bug has been logged on the website:

Bug reference:      8246
Logged by:          sandeep
Email address:      msandeep27@gmail.com
PostgreSQL version: 8.4.17
Operating system:   windows 7
Description:

Hi All,
I have a database containing 10 tables say as t1 ,t2,t3,t4......t10.There is
a column in t1 which is primary key and that primary key to other tables
(i.e t2 t3.... t10). Now when ingesting data i am able to ingest it around
nearly able 1 lakh rows in secs. now i want to delete the primary key from
t1 so that the data other tables data get deleted.But since the data is huge
approx 1.5 rows get affected its taking 6 minutes to delete it. Is there
something that can be done .