SQL Relay 是一个持久化的数据库连接池，用来为 Unix 或者 Linux 提供数据库连接池、代理以及负载均衡的功能。
SQL Relay 的应用思路：
- 加速数据库驱动的基于 Web 的应用程序
- 增加 Web 应用程序的可扩展性
- 分布式的访问复制的数据库系统
- 对数据库访问进行节流
- 从不被支持的平台上访问某个数据库
- 可以轻松的对数据库系统进行移植
SQL Relay 0.48 改进记录：
- Several contributed updates have been integrated.
- The stmtcachesize parameter now enables use of the Oracle Statement Cache.
- Most of the server-side code has been reorganized to be more modular, and several things have been reimplemented as plugins.
- Several performance improvements have been made.
- One eliminates an unnecessary client-server roundtrip and another eliminates an unnecessary re-prepare