support full text searching using Postgresql v10’s new full text searching features. 

Starting from Team Foundation Server 2017, the Code Search feature that was available for a while in VSTS, gets an on-premise equivalent.
The feature is built on top of a customized version of ElasticSearch. However the integration between the 2 products(TFS and ElasticSearch) is rather limited right now.

First official public Beta release of Lucene.NET 4.8! 

How we reindexed 36 billion documents in 5 days within the same Elasticsearch cluster 

We are about to release Lucene.NET 4.8, and it's time to show what it can do, and how it can be done. 

MongoDB, one of the leading NoSQL databases, is well known for its fast performance, flexible schema, scalability and great indexing capabilities. At the core of this fast performance lies MongoDB indexes, which support efficient execution of queries by avoiding full-collection scans and hence limiting the number of documents MongoDB searches.

Introduction to Lucene
Lucene Components Overview
Lucene Query (Search) Syntax Examples
Advanced Lucene Query Examples
Building a Search Index with Lucene
Integrating Lucene Search into an Application
Lucene Analysis Process Guide