# F.41.tcn
这个tcn
模块提供了一个触发器函数,用于通知侦听器它所连接的任何表的更改。它必须用作之后
触发每行
.
该模块被认为是“受信任的”,也就是说,它可以由拥有创造
当前数据库的权限。
一个函数中只能提供一个参数创建触发器
语句,这是可选的。如果提供,它将用于通知的通道名称。如果省略tcn
将用作频道名称。
通知的有效负载包括表名、指示执行了哪种类型的操作的字母,以及主键列的列名/值对。每个部分用逗号隔开。为了便于使用正则表达式进行解析,表名和列名总是用双引号括起来,数据值总是用单引号括起来。嵌入的报价增加了一倍。
下面是使用扩展的一个简单示例。
test=# create table tcndata
test-# (
test(# a int not null,
test(# b date not null,
test(# c text,
test(# primary key (a, b)
test(# );
CREATE TABLE
test=# create trigger tcndata_tcn_trigger
test-# after insert or update or delete on tcndata
test-# for each row execute function triggered_change_notification();
CREATE TRIGGER
test=# listen tcn;
LISTEN
test=# insert into tcndata values (1, date '2012-12-22', 'one'),
test-# (1, date '2012-12-23', 'another'),
test-# (2, date '2012-12-23', 'two');
INSERT 0 3
Asynchronous notification "tcn" with payload ""tcndata",I,"a"='1',"b"='2012-12-22'" received from server process with PID 22770.
Asynchronous notification "tcn" with payload ""tcndata",I,"a"='1',"b"='2012-12-23'" received from server process with PID 22770.
Asynchronous notification "tcn" with payload ""tcndata",I,"a"='2',"b"='2012-12-23'" received from server process with PID 22770.
test=# update tcndata set c = 'uno' where a = 1;
UPDATE 2
Asynchronous notification "tcn" with payload ""tcndata",U,"a"='1',"b"='2012-12-22'" received from server process with PID 22770.
Asynchronous notification "tcn" with payload ""tcndata",U,"a"='1',"b"='2012-12-23'" received from server process with PID 22770.
test=# delete from tcndata where a = 1 and b = date '2012-12-22';
DELETE 1
Asynchronous notification "tcn" with payload ""tcndata",D,"a"='1',"b"='2012-12-22'" received from server process with PID 22770.