For those who have RDBMS you most likely need to use Solr to index your relational tables to completely nested documents.

Im a new comer to non-sql databases like Mongodb, CouchDB and Cassandra, however it appears in my experience the data it will save you has already been for the reason that document structure such as the documents held in Solr/Lucene.

Performs this imply that it's not necessary to use Solr/Lucene when utilizing these databases?

Could it be already indexed to ensure that that you can do full-text search?

It is dependent in your needs. There is a full text search. In CouchDB the search is Lucene (just like solr). Regrettably, case a complete text index, if you want complex scoring or DisMax type searching, you will probably want the additional abilities of the independent Solr Index.

Solr (Lucene) uses an formula to returns relevant documents from the query. It'll returns a score to point how relevant each document relates to the query.

It differs from exactly what a database (relational or otherwise) does, that is coming back results that suits or otherwise a question.