Apache Solr 是一个开源的搜索服务器。Solr 使用 Java 语言开发，主要基于 HTTP 和 Apache Lucene 实现。
Apache Solr 6.4.2 主要组件版本：
Apache Tika 1.13
Carrot2 3.15.0
Velocity 1.7 和 Velocity Tools 2.0
Apache UIMA 2.3.1
Apache ZooKeeper 3.4.6
Jetty 9.3.14.v20161028
Bug 修复：
Serious performance degradation in Solr 6.4.1 due to the new metrics collection. Default settings in solrconfig.xml /config/indexConfig/metrics have been changed to turn off IndexWriter metrics collection. Directory level metrics collection has been completely removed until a better design is found.
Transaction log replay can hit an NPE due to new Metrics code.
Fix instanceof check in ConstDoubleSource.equals
Fix NPE in CloudSolrClient when reading stale alias
Fix copy/paste in solr-ltr pom.xml template.
下载地址：
http://www.apache.org/dyn/closer.lua/lucene/solr/6.4.2
来自:开源中国社区
