Finding the size of ActiveRecord objects

Hi all,

Is there a way to find the size of an ActiveRecord object on the disk?
The idea is that a user has a certain amount of disk space allocated
to them and they can create various objects until they run out of
space. Is this possible?

Many thanks,

Sounds like a lot of this will depend on how the database stores the
rows (eg how long are numerical columns etc..., are rows packed