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Solr is the popular, blazing fast, open source NoSQL search platform from the Apache Lucene Solr project. Its major features include powerful full-text search, hit highlighting, faceted search and analytics, rich document parsing, geospatial search, extensive REST APIs as well as parallel SQL. Solr is enterprise grade, secure and highly scalable, providing fault tolerant distributed search and indexing, and powers the search and navigation features of many of the world's largest internet sites.
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A summary of important changes is published in the Solr Reference Guide at https://lucenesolr.apache.org/solr/guide/8_11/solr-upgrade-notes.html. For the most exhaustive list, see the full release notes at https://lucenesolr.apache.org/solrdocs/8_11_0/changes/Changes.html or by viewing the CHANGES.txt file accompanying the distribution. Solr's release notes usually don't include Lucene layer changes. Lucene's release notes are at https://lucene.apache.org/core/8_11_0/changes/Changes.html