Lucene is an open-source search library developed by Apache that provides the core functionality needed for indexing and searching text-based data. It is widely used for building search engines and other information retrieval (IR) systems. Lucene operates using an inverted index, where each word in the corpus is mapped to the documents containing it, enabling efficient full-text search.
Lucene is typically used as the underlying engine in larger systems, such as Apache Solr and Elasticsearch, to manage indexing, searching, and ranking tasks. It supports features like tokenization, stemming, and phrase searches, which are crucial for making search results more accurate.
While Lucene does not include a built-in user interface or distributed capabilities, it provides developers with the flexibility to customize and scale the search infrastructure as needed, making it a popular choice for developers building custom search applications.