Postgres UPSERT (INSERT or UPDATE) only if value is different

Question

I\'m updating a Postgres 8.4 database (from C# code) and the basic task is simple enough: either UPDATE an existing row or INSERT a new one if one doesn\'t exist yet. Normally I

Answer 1

Take a look at a BEFORE UPDATE trigger to check and set the correct values:

CREATE OR REPLACE FUNCTION my_trigger() RETURNS TRIGGER LANGUAGE plpgsql AS
$$
BEGIN
    IF OLD.content = NEW.content THEN
        NEW.updated_time= OLD.updated_time; -- use the old value, not a new one.
    ELSE
        NEW.updated_time= NOW();
    END IF;
    RETURN NEW;
END;
$$;

Now you don't even have to mention the field updated_time in your UPDATE query, it will be handled by the trigger.

http://www.postgresql.org/docs/current/interactive/plpgsql-trigger.html