I haven't seen an issue describing this. Something like this was available
in the SOLR-236 patches, but never got committed.
I started to create a second pass collector that counts the distinct values
of a particular field for the top N groups in LUCENE-3444.
I think there might be a need for a
It is a fairly typical use case due to the availability of aggregation
functions in combination with GROUP BY in SQL. Conceptually, given the
work that has already been completed with Lucene's group by
functionality these may be simple add ons.
A couple of features that would effectively
