Natural Language Processing

Apache Lucene – full-featured text search engine library

Apache Lucene is an open source high-performance, full-featured information retrieval software library written entirely in Java. It is a technology suitable for nearly any application that requires full-text search, especially cross-platform.

Apache Lucene sets the standard for search and indexing performance. Lucene itself is just an indexing and search library and does not contain crawling and HTML parsing functionality.

It is supported by the Apache Software Foundation and is released under the Apache Software License. Lucene has been ported to other programming languages including Delphi, Perl, C#, C++, Python, Ruby, and PHP.

Features include:

  • 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.
    • Static index pruning (Carmel pruning) removes postings with low within-document term frequency.
  • 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:
    • 100%-pure Java.
    • Implementations in other programming languages available that are index-compatible.

Support: Documentation
Developer: Apache Software Foundation
License: Apache License 2.0

Apache Lucene is written in Java. Learn Java with our recommended free books and free tutorials.

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