The official documentation has moved to http://docs.couchdb.org — The transition is not 100% complete, but http://docs.couchdb.org should be seen as having the latest info. In some cases, the wiki still has some more or older info on certain topics inside CouchDB.
Full-text Indexing and Searching
Lucene integration with CouchDB is available with an external project called couchdb-lucene (http://github.com/rnewson/couchdb-lucene).
elasticsearch is an open source, distributed, RESTful, Search Engine.
ElasticSearch integration with CouchDB is possible by using an Elasticsearch couchdb river plugin