Checking my HD space (noarchive)

Hi All,

My bare text table is in size around 6Mb while the footprint of my database
on HD (using du) is around 24Mb (after a vacuum -f)
I have normalized the tables on places where I could do it.
For your reference it's a squid2.2 access.log textfile.
How can I check witch tables/indexes takes up so much space?

And I did understand that postgresql can compress text but it seems that
this is not the default case.
can anybody tell me somthing about it and/or point my to a url??

Ries