PostgreSQL inherited table and insert triggers - sql

Question

I'm trying to follow the advice here to create a vertically partitioned table for storing time series data.
So far, my schema looks like this:
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);
Now I'm trying to create an INSTEAD OF INSERT trigger so that events can be inserted on the events table and the row will end up in the right sub-table. But the documentation says that INSTEAD OF INSERT triggers can only be created on views, not tables (or subtables):
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.
What's the right way of doing this?

Answer 1

You need to declare BEFORE INSERT triggers.
Documentation on partitioning is a great source of knowledge in this matter and is full of examples.
Example function from docs
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;
Example trigger from docs
CREATE TRIGGER insert_measurement_trigger
BEFORE INSERT ON measurement
FOR EACH ROW EXECUTE PROCEDURE measurement_insert_trigger();
Returning NULL from BEFORE trigger will keep the parent table empty.