PostgreSQL学习第十四篇 listen与notify

PostgreSQL提供了client端之间通过服务器端进行消息通信的机制。这种机制是通过listen和notify命令来完成的。session1：postgres=# listen postgres;LISTENpostgres=# listen limingpostgres-# ;LISTENsession2：postgres=# notify postgres,'hello Word';NOTIFYpostgres=# notify liming,'hello liming';NOTIFYpostgres=#session1；postgres=# select 1;   --随便执行了一个命令 ?column?----------        1(1 row)Asynchronous notification "postgres" with payload "hello word" received from server PRocess with PID 12241.Asynchronous notification "liming" with payload "hello liming" received from server process with PID 12241.postgres=#  listen和notify的相关命令：	1. listen：监听消息通道	2. unlisten：取消先前的监听	3. notify：发送消息到消息通道中	4. pg_notify()：与notify命令功能相同	5. pg_listening_channels()：调用此函数可以查询当前session已注册了哪些消息监听