As we sometimes have to face some very special needs on search, we had to customize our object indexing by integrating some dedicated attributes in search index.

As their scope was only search and we had several of them, we wanted to avoid the creation of a datatype/attribute for each. Obviously, we also wanted to avoid hardcoded indexing changes in eZ Find classes.
We then though and wrote a support for a kind of attributes that only have a sense for eZ Find, driven by handlers and dedicated to search/facets : that's what we call "Virtual Attributes".
The change on eZ Find source code is finally quite minor, whereas this will allow a strong customization.

It's currently working great on some of our production projects and, as this is finally a common need, we decided to share it there. It also gives a proof of concept of a small feature that, to our eyes, could even have a reason to live in eZ Find.

You'll find attached the patch file (to be applied against eZ Find 2.0.0 source code), a sample handler and a readme file that describes the feature and how to use it (files are indeed packed as I can submit only one file).
Hope this will be useful,

DoDeV / AlNio