PostgreSQL 继承表和插入触发器

Question

我正在尝试按照此处的建议创建一个用于存储时间序列数据的垂直分区表。

到目前为止，我的架构如下所示：

CREATE TABLE events 
(
     topic text, 
     t timestamp, 
     value integer, 
     primary key(topic, t)
);

CREATE TABLE events_2014 
(
     primary key (topic, t), 
     check (t between '2014-01-01' and '2015-01-01') 
) INHERITS (events);

现在我正在尝试创建一个INSTEAD OF INSERT触发器，以便可以在events表中插入事件，并且该行将最终出现在正确的子表中。但是文档说INSTEAD OF INSERT触发器只能在视图上创建，不能在表（或子表）上创建：

CREATE OR REPLACE FUNCTION insert_events () RETURNS TRIGGER AS $insert_events$ BEGIN
  IF new.t between '2014-01-01' and '2015-01-01' THEN
    INSERT INTO events_2014 SELECT new.*;
  ...
  END IF
  RETURN NULL;
END;
$insert_events$ LANGUAGE PLPGSQL;

CREATE TRIGGER insert_events INSTEAD OF INSERT ON events FOR EACH ROW EXECUTE PROCEDURE insert_events();
ERROR:  "events" is a table
DETAIL:  Tables cannot have INSTEAD OF triggers.

这样做的正确方法是什么？

Answer 1

您需要声明BEFORE INSERT触发器。

关于分区的文档是这方面知识的重要来源，并且包含大量示例。

来自文档的示例函数

CREATE OR REPLACE FUNCTION measurement_insert_trigger()
RETURNS TRIGGER AS $$
BEGIN
    IF ( NEW.logdate >= DATE '2006-02-01' AND
         NEW.logdate < DATE '2006-03-01' ) THEN
        INSERT INTO measurement_y2006m02 VALUES (NEW.*);
    ELSIF ( NEW.logdate >= DATE '2006-03-01' AND
            NEW.logdate < DATE '2006-04-01' ) THEN
        INSERT INTO measurement_y2006m03 VALUES (NEW.*);
    ...
    ELSIF ( NEW.logdate >= DATE '2008-01-01' AND
            NEW.logdate < DATE '2008-02-01' ) THEN
        INSERT INTO measurement_y2008m01 VALUES (NEW.*);
    ELSE
        RAISE EXCEPTION 'Date out of range.  Fix the measurement_insert_trigger() function!';
    END IF;
    RETURN NULL;
END;
$$
LANGUAGE plpgsql;

文档中的示例触发器

CREATE TRIGGER insert_measurement_trigger
    BEFORE INSERT ON measurement
    FOR EACH ROW EXECUTE PROCEDURE measurement_insert_trigger();

NULL从BEFORE触发器返回将使父表保持为空。