Java 搜索引擎 Lucene 3.5 發布

Lucene是一套用于全文檢索和搜尋的開源程式庫，由Apache軟件基金會支持和提供。Lucene提供了一個簡單確強大的應用程式接口，能夠做全文索引和搜尋，在Java開發環境里Lucene是一個成熟的免費開放源代碼工具;就其本身而論，Lucene是現在并且是這幾年，最受歡迎的免費java資訊檢索程式庫。人們經常提到資訊檢索程式庫，就像是搜尋引擎，但是不應該將資訊檢索程式庫與網搜索引擎相混淆。

Lucene最初是由Doug Cutting所撰寫的，是一位資深全文索引/檢索專家，曾經是V-Twin搜索引擎的主要開發者，后來在Excite擔任高級系統架構設計師，目前從事 于一些INTERNET底層架構的研究。他貢獻出Lucene的目標是為各種中小型應用程式加入全文檢索功能。

項目地址：http://lucene.apache.org/

Apache Lucene 3.5 發布了，該版本包含大量的bug修復、優化以及改進，下載地址：

http://www.apache.org/dyn/closer.cgi/lucene/java

完整改進內容請看下載后的 CHANGES.txt 文件。

Lucene 3.5.0 值得關注的改進：

• Added a very substantial (3-5X) RAM reduction required to hold the terms index on opening an IndexReader. (LUCENE-2205)
• Added IndexSearcher.searchAfter which returns results after a specified ScoreDoc (e.g. last document on the previous page) to support deep paging use cases. (LUCENE-2215)
• Added SearcherManager to manage sharing and reopening IndexSearchers across multiple search threads. Underlying IndexReader instances are safely closed if not referenced anymore. (LUCENE-3445, LUCENE-3558)
• Added SearcherLifetimeManager which safely provides a consistent view of the index across multiple requests (e.g. paging/drilldown). (LUCENE-3558, LUCENE-3486)
• Renamed IndexWriter.optimize to forceMerge to discourage use of this method since it is horribly costly and rarely justified anymore. (LUCENE-3439)
• Added NGramPhraseQuery that speeds up phrase queries 30-50% when n-gram analysis is used. (LUCENE-3426)
• Added a new reopen API (IndexReader.openIfChanged) that returns null instead of the old reader if there are no changes in the index. (LUCENE-3464)
• Improvements to vector highlighting: support for more queries such as wildcards and boundary analysis for generated snippets (LUCENE-1824, LUCENE-1889)
• IndexSearcher and IndexReader now perform additional checks to throw AlreadyClosedExceptions if searches are performed on a closed IndexReader. Performing searches on already closed reader can cause JVM crashes when invalid memory mapped files are referenced.
• Several bugfixes, including a bug where closing an NRT reader after the writer was closed was incorrectly invoking the DeletionPolicy.