Trigger on every update or insert - sql

Question

I want to create trigger that fires every time any column is changed - whether it is freshly updated or new insert. I created something like this:
CREATE TRIGGER textsearch
BEFORE INSERT OR UPDATE
ON table
FOR EACH ROW
EXECUTE PROCEDURE trigger();
and body of trigger() function is:
BEGIN
NEW.ts := (
SELECT COALESCE(a::text,'') || ' ' ||
COALESCE(b::int,'') || ' ' ||
COALESCE(c::text,'') || ' ' ||
COALESCE(d::int, '') || ' ' ||
COALESCE(e::text,'')
FROM table
WHERE table.id = new.id);
RETURN NEW;
END
I hope it is clear what I want to do.
My problem is that trigger fires only on update, not on insert. I guess that this isn't working because I have BEFORE INSERT OR UPDATE, but if I change it to AFTER INSERT OR UPDATE then it doesn't work neither for INSERT nor UPDATE.

Answer 1

you need to use the NEW record directly:
BEGIN
NEW.ts := concat_ws(' ', NEW.a::text, NEW.b::TEXT, NEW.c::TEXT);
RETURN NEW;
END;
The advantage of concat_ws over || is that concat_ws will treat NULL values differently. The result of 'foo'||NULL will yield NULL which is most probably not what you want. concat_ws will use an empty string NULL values.

Answer 2

It doesn't work because you're calling SELECT inside the function.
When it runs BEFORE INSERT then there isn't a row to select, is there?
Actually, BEFORE UPDATE you'll see the "old" version of the row anyway, won't it?
Just directly use the fields: NEW.a etc rather than selecting.
As an edit - here is an example showing what the trigger function can see. It's exaclty as you'd expect in a BEFORE trigger.
BEGIN;
CREATE TABLE tt (i int, t text, PRIMARY KEY (i));
CREATE FUNCTION trigfn() RETURNS TRIGGER AS $$
DECLARE
sv text;
BEGIN
SELECT t INTO sv FROM tt WHERE i = NEW.i;
RAISE NOTICE 'new value = %, selected value = %', NEW.t, sv;
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER trigtest BEFORE INSERT OR UPDATE ON tt FOR EACH ROW EXECUTE PROCEDURE trigfn();
INSERT INTO tt VALUES (1,'a1');
UPDATE tt SET t = 'a2' WHERE i = 1;
ROLLBACK;

Answer 3

in your COALESCE statements when you cast b::int i had to change your coalesce to use integer place holder instead. As mentioned by a_horse_with_no_name this can end up with null values but you can see how to make your specific code example run. I included the "RAISE NOTICE" lines for debug purposes only.
Based on your provided information the following works for me:
CREATE TABLE my_table (id SERIAL NOT NULL,a TEXT,b INTEGER,c TEXT,d INTEGER,e TEXT);
CREATE OR REPLACE FUNCTION my_triggered_procedure() RETURNS trigger AS $$
BEGIN
if(TG_OP = 'UPDATE' OR TG_OP = 'INSERT') THEN
NEW.ts := (SELECT COALESCE(a::text,'') || ' ' ||
COALESCE(b::int,0) || ' ' ||
COALESCE(c::text,'') || ' ' ||
COALESCE(d::int, 0) || ' ' ||
COALESCE(e::text,'')
FROM my_table
WHERE id=NEW.id);
RAISE NOTICE 'INSERT OR UPDATE with new ts = %',NEW.ts;
RETURN NEW;
ELSIF (TG_OP = 'DELETE') THEN
OLD.ts := ' ';
RAISE NOTICE 'DELETED old id: %',OLD.id;
RETURN OLD;
END IF;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER text_search
AFTER INSERT OR UPDATE OR DELETE
ON my_table
FOR EACH ROW
EXECUTE PROCEDURE my_triggered_procedure();
INSERT INTO my_table (a,b,c,d,e) VALUES('text11',12,'text21',3,'text4');
>NOTICE: INSERT OR UPDATE with new ts = text11 12 text21 3 text4
>INSERT 0 1
DELETE FROM my_table WHERE id=24;
>NOTICE: DELETED ID = 24
>DELETE 1
PostgreSQL::Trigger Procedures