Apache Solr
Solr is a stand alone enterprise search server which applications communicate with using XML and HTTP to index documents, or execute searches. Solr supports a rich schema specification that allows for a wide range of flexibility in dealing with different document fields, and has an extensive search plugin API for developing custom search behavior.
Solr itself is a Java Application, but all interaction with Solr is done by POSTing messages over HTTP (in JSON, XML, CSV, or binary formats) to index documents and GETing search results back as JSON, XML, or a variety of other formats (Python, Ruby, PHP, CSV, binary, etc…)
Solr requires Java 1.5 and an Application server (such as Tomcat) which supports the Servlet 2.4 standard.
Solr is currently being used to power search applications on several high traffic publicly accessible websites like Google.
Google one of powerful company that using solr, Google is arguably the world’s largest open-source company, not only releasing a minimum of 14 million lines of open-source code but also hosting over 250,000 open-source projects on Google Code, in addition to its open-source advocacy work like Summer of Code.
need to know more about solr visit http://wiki.apache.org/solr/FAQ
Solr is currently being used to power search applications on several high traffic publicly accessible websites.
