Common Index with personalized fields

[Ravikumar Govindarajan <ra...@gmail.com>]

We have a system where N number of users are tied to a particular lucene
index. Sort of "Shared Index".

But each of the N users can have their own personalized fields.

Ex: Every E-mail to lucene mailing-list is a document
     Every user part of this mailing-list has his own set of labels for
that e-mail.

What is the best way to capture this info correctly in lucene?

1. Duplicate the same E-mail for N users and keep the indexes  separate for
each of them?

2. Hold a common index but with certain fields personalized for each user,
in every document? In the above example, the field LABEL repeats as many
times as there are users in group, for every delivered E-Mail

3. A user may be part  5-10 groups on an average. A given group contains
5-10 users on an average

Are there any known approaches documented by lucene-community, that I can
refer to.

--
Ravi