Apache Lucene Core

Apache Lucene™ is ahigh-performance, full-featured search engine library written entirely in Java.It is a technology suitable for nearly any application that requires structuredsearch, full-text search, faceting, nearest-neighbor search acrosshigh-dimensionality vectors, spell correction or query suggestions.

Apache Lucene is an open source project available for free download. Please use thelinks on the right to access Lucene.

Lucene™ Features

Lucene offers powerful features through a simple API:

Scalable, High-Performance Indexing

• over800GB/hour on modern hardware
• small RAM requirements -- only 1MB heap
• incremental indexing as fast as batch indexing
• index size roughly 20-30% the size of text indexed

Powerful, Accurate and Efficient Search Algorithms

• ranked searching -- best results returned first
• many powerful query types: phrase queries, wildcard queries, proximity queries, range queries and more
• fielded searching (e.g. title, author, contents)
• nearest-neighbor search for high-dimensionality vectors
• sorting by any field
• multiple-index searching with merged results
• allows simultaneous update and searching
• flexible faceting, highlighting, joins and result grouping
• fast, memory-efficient and typo-tolerant suggesters
• pluggable ranking models, including theVector Space Model andOkapi BM25
• configurable storage engine (codecs)

Search performance of Apache Lucene is tracked in muliple places. Check out

• Mike McCandless' nightly benchmarks for Lucene for an historical view of Lucene's query performance, going back to 2011 for some queries
• Search Benchmark, the Game for a comparison of Lucene with other search engines

Cross-Platform Solution

• Available as Open Source software under theApache License which lets you use Lucene in both commercial and Open Source programs
• 100%-pure Java
• Implementationsin other programming languages available