Cassandra Full-Text Search

AFAIK Datastax Enterprise Search is the (commercial) successor of Solandra.

Cassandra 2.0 supports so called "custom secondary indexes". Custom secondary indexes are Java code. Your own implementation has to implement the abstract class org.apache.cassandra.db.index.SecondaryIndex (See http://www.datastax.com/documentation/cql/3.1/cql/cql_reference/create_index_r.html)

I'm not sure whether implementations exist for Elasticsearch or Solr.

I would not recommend to code all the weird full text search logic like stemming, multiple/exotic language support or even geo spatial stuff.

But SecondaryIndexwould be a good point to start integrating your favorite search engine.

If your dataset is relative small you can simply use a inmemory instance of lucene, update the index at a set interval and you are ready to go.