Sphinx

Sphinx: Free open-source SQL full-text search engine

Features

high indexing speed (upto 10 MB/sec on modern CPUs);
high search speed (avg query is under 0.1 sec on 2-4 GB text collections);
high scalability (upto 100 GB of text, upto 100 M documents on a single CPU);
provides good relevance ranking through combination of phrase proximity ranking and statistical (BM25) ranking;
provides distributed searching capabilities;
provides document exceprts generation;
provides searching from within MySQL through pluggable storage engine;
supports boolean, phrase, and word proximity queries;
supports multiple full-text fields per document (upto 32 by default);
supports multiple additional attributes per document (ie. groups, timestamps, etc);
supports stopwords;
supports both single-byte encodings and UTF-8;
supports English stemming, Russian stemming, and Soundex for morphology;
supports MySQL natively (MyISAM and InnoDB tables are both supported);
supports PostgreSQL natively.

用 PHP 构建自定义搜索引擎: 使用 Sphinx 索引内容、快速查找文本并提供有用的搜索结果