Meta-search by subclassing SearchHandler

[Dan Davis <da...@gmail.com>]

I am considering enabling a true "Federated Search", or meta-search, using
the following basic configuration (this configuration is only for
development and evaluation):

Three Solr cores:

   - One to search data I have indexed locally
   - One with a custom SearchHandler that is a facade, e.g. it performs a
   meta-search (aka Federated Search)
   - One that queries and merges the above cores as "shards"

Lest I seem completely like Sauron, I read
http://2011.berlinbuzzwords.de/sites/2011.berlinbuzzwords.de/files/AndrzejBialecki-Buzzwords-2011_0.pdf
and am familiar with evaluating "precision at 10", etc. although I am no
doubt less familiar with IR than many.

I think that it is much, much better for performance and relevancy to index
it all on a level playing field.  But my employer cannot do that, because
we do not have a license to all the data we may wish to search in the
future.

My questions are simple - has anybody implemented such a SearchHandler that
is a facade for another search engine?   How would I get started with that?

I have made a similar post on the blacklight developers google group.