Data Mart with Postgres

Hello everybody,

I´m working with a small project to a client, using Postgres to store data in a dimensional model, fact-oriented, e.g., a Datamart.

At this time, all I have is a populated database, with the "star schemma" common relations (PK´s / FK´s).

Below is a list of the main goals of this project :
1. Front-end app (PHP5)
2. Transactional database for this app (Postgres)
3. Datamart in Postgres (described above)
4. ROLAP server that supports Postgres (Java - Mondrian)
5. Front-end app to manage querys to the ROLAP server (JSP - JPivot)

Users will have web access to (1), and will be enable to create views using (5).

It seems like I´m trying to reinvent the wheel, but the point here is that the client can´t afford to use proprietary BI solutions, nor proprietary OS.
What I have read all across the internet is that Postgres does not support this kind of application, wich demands materialyzed views, built-in bitmap index, and so on. In the open-source world, I find those missing features with Mondrian/JPivot.

Does anyone has ever used this structure before ? At least Mondrian and JPivot ?