Solr is the most popular enterprise search engine in the world. It’s 100% open-source from Apache Software Foundation, and is blazing fast, feature rich and scalable. Its major features include powerful full-text search, hit highlighting, faceted search, dynamic clustering, GEO search, field collapsing and rich document handling. Solr can be secured with Authentication, Role based Authorization and SSL. Solr scales linearly, enabling you to index billions of documents/rows by simply adding more hardware. Solr is powering many high-profile internet sites within e-commerce, online media, yellow-pages. It is also the preferred choice for Big Data vendors for indexing Hadoop content. See this list of known public servers.
Solr is written in Java and runs as a standalone full-text search server. Solr uses the Lucene search library at its core for full-text indexing and search, and provides industry standard REST-like HTTP interfaces as well as APIs for most programming languages. Solr is the most extensible search server, enabling you to plug in your own implementations of such things as Query Parsers, Request Handlers, Update Handlers, Document Processors, Search Components, Analyzers, Tokenizers, Stemmers, Authentication, Authorization and more. And if there is no plugin interface, you can always write a patch to change the Java source code.
That being said, Solr does not require any programming skills to get started. Everything you need to get your data in and searchable is done through easy configuration and simple tools.
Read more about Solr at the Apache site.