Solr is a standalone enterprise search server with a web-services like API. It extends Lucene:
- Real schema, with numeric types, dynamic fields, unique keys
- Powerful extensions to the lucene query language
- Support for dynamic faceted browsing and filtering
- Advanced, configurable text analysis
- Highly configurable and user extensible caching
- Performance optimizations
- External configuration via xml
- An administration interface
- Monitorable logging
- Fast incremental updates and snapshot distribution
- XML and CSV/delimited-text update formats