How to store tree data in a Lucene/Solr/Elasticsearch index or a NoSQL db?

Question

Say instead of documents I have small trees that I need to store in a Lucene index. How do I go about doing that?

An example node in the tree:

class          


        

Answer 1

This requirement and the solution is captured here: Proposal for nested docs

This design was subsequently implemented both by core Lucene and Elastic Search. The BlockJoinQuery is the core Lucene implementation and Elastic Search look to have an implementation as outlined here: Elastic search nested docs