pg_notify() 是一个系统函数，用于向连接到同一数据库并监听指定通道的其他会话发送通知，该通道使用 LISTEN 命令指定。
pg_notify() 添加于 PostgreSQL 9.0。
用法
pg_notify (text,text) →void
pg_notify() 提供了等效于 NOTIFY 命令的功能，但允许从表、表达式或其他数据源派生通道名称（第一个参数）和（可选）消息（第二个参数）。它还允许使用单个查询发送多个通知。
有关更多详细信息，请参阅 NOTIFY。
变更历史
- PostgreSQL 9.0
- 添加 (提交 d1e02722)
示例
基本的 pg_notify() 用法示例（为了简化起见，显示了在同一通道上监听的会话）
postgres=# LISTEN foo; LISTEN postgres=# SELECT pg_notify('foo', 'hello world'); pg_notify ----------- (1 row) Asynchronous notification "foo" with payload "hello world" received from server process with PID 4145118.
这等效于执行 NOTIFY 'foo', 'hello world'。
如果消息指定为 NULL 或 ''（空字符串），则将发送不带消息的通知
postgres=# LISTEN foo;
LISTEN
postgres=# LISTEN bar;
LISTEN
postgres=# SELECT pg_notify('foo', NULL), pg_notify('bar', '');
pg_notify | pg_notify
-----------+-----------
|
(1 row)
Asynchronous notification "foo" received from server process with PID 4145118.
Asynchronous notification "bar" received from server process with PID 4145118.
上述函数调用等效于在事务中执行 NOTIFY foo 和 NOTIFY bar。
发送从表中生成的邮件
postgres=# CREATE TABLE notifications(channel NAME NOT NULL, message TEXT);
CREATE TABLE
postgres=# INSERT INTO notifications VALUES
('foo', 'bar'),
('foo', 'the date is ' || current_date);
INSERT 0 2
postgres=# SELECT pg_notify(channel, message) FROM notifications;
pg_notify
-----------
(2 rows)
Asynchronous notification "foo" with payload "bar" received from server process with PID 4154810.
Asynchronous notification "foo" with payload "the date is 2021-06-18" received from server process with PID 4154810.
参考文献
- PostgreSQL 文档： pg_notify