Apache Lucene

Apache Lucene™ is a high-performance, full-featured text search engine library written entirely in Java. It is a technology suitable for nearly any application that requires full-text search, especially cross-platform.

Lucene offers powerful features through a simple API:

Scalable, High-Performance Indexing

• over 150GB/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)
• 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 the Vector Space Model and ;Okapi BM25
• configurable storage engine (codecs)

Cross-Platform Solution

• Available as Open Source software under the Apache License which lets you use Lucene in both commercial and Open Source programs
• 100%-pure Java
• Implementations in other programming languages available that are index-compatible