Github user MikeThomsen commented on the issue:
https://github.com/apache/nifi/pull/2517
> should be an expectation that there is some commonality between them.
Solr and ES are increasingly used for different use cases these days. Solr
tends to be more commonly used for pure search whereas ES is frequently used
for data analysis because it has really powerful and fast aggregation queries
that Solr lacks.---
