Partition database between users and implement disk quotas

Hello,

I wrote an aplication where I store data from different users whithin the
same database. There is no link between data of different users.

In my current implementation, I added a column "user_id" in each table,
and, with views and rules mechanisms, I am able to hide data from other
users. Everything works fine and I am happy with this solution. But I now
have another need : I would want to measure the disk usage of each user
such that I can restrict the access to the database when a user exceeds its
limit.

I envisaged three solutions to solve this problem, but I do not know which
one would be the best :

Solution1 : keep the same database layout, and count the size of each
record of a user. As some columns have variable sizes, this is not a really
simple solution. And I have no idea on how to take into account index and
stuff like that. I am not sure this solution is feasible and, if yes, I
fear it will not be efficient to compute disk usage on this way.

Solution 2 : use a separate database for each client. This solution is
probably the simplest one. But, one of the advantage of my previous
solution was that I was able to use connection pool to connect to my
database as all users are using the same database with same db user (access
is provided via a web service). With this solution, this will no more be
possible: I will need a dedicated connection for each user. A second
problem I am fearing is that I have a lot of clients (several hundreds) and
I am not sure this is a good idea to create so much database on the same
server.

Solution 3 : use the table partitionning mechanism. I never used this
feature, but from what I read in the doc, it seems that I could use this
mechanism to put data from different clients in different partitions. As
each partition is a dedicated sub-table, I suppose I could use dedicated
postgresql mechanism to compute its size (including associated index and so
on). I really think this solution is well fitted to my need. The only thing
that I fear is that I don't know if it's a good idea to partition a table
in hundreds of different partitions ?

So, does someone has good advices to solve my problem ? Maybe there is
another solution that I am not aware of ?

Thanks in advance for your help,
Brice