Postgresql multiple columns in ON CONFLICT

Question

I want to only insert a row if every cell in that row is unique (excluding the id field of course) so I tried this

INSERT INTO test (val, val2, val3) VALUES ('g', 'h', 'j') 
ON CONFLICT (val, val2, val3) DO NOTHING RETURNING id;

But turns out that this is invalid because the fields passed to ON CONFLICT must be constrained with UNIQUE . But I don't want that, I only want permutations of val, val2 and var3 to be unique, I don't want them to be unique individually. And after the INSERT, no matter if it inserted or not I want to return the id field. How may I do this?

Answer 1

I solved this by creating the UNIQUE like this:

CREATE TABLE test (
  id SERIAL,
  val varchar(100),
  val2 varchar(100),
  val3 varchar(100),
  UNIQUE (val, val2, val3)
);

and then inserting like this:

INSERT INTO test (val, val2, val3) VALUES ('a', 'b', 'c') ON CONFLICT (val, val2, val3) DO UPDATE SET val='a' RETURNING id;

even if there is nothing to update, it makes it return the id