Lucene
Search Engine that's part of Apache Jakarta. Which means it's written in Java - but there's a LuPy wrapper...
http://jakarta.apache.org/lucene/
Lucene Desktop Search? <http://www.peerfear.org/rss/permalink/2004/10/28/Lots Of Interest In Lucene Desktop/>
ElasticSearch is a search server based on Lucene. It provides a distributed, multitenant-capable full-text search engine with an HTTP web interface and schema-free JSON documents. Elasticsearch is developed in Java and is released as open source under the terms of the Apache License. Elasticsearch is the most popular enterprise search engine followed by Apache Solr, also based on Lucene. https://en.wikipedia.org/wiki/Elasticsearch
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