-- M5c: persist unmatched-similar-artist MBIDs that the M4b worker would
-- otherwise discard. Mirrors artist_similarity shape: same composite PK
-- with source, same (seed_id, score DESC) index, same source enum check.
-- The candidate side is text + name (no FK) — that's the whole point.

CREATE TABLE artist_similarity_unmatched (
    seed_artist_id  uuid              NOT NULL REFERENCES artists(id) ON DELETE CASCADE,
    candidate_mbid  text              NOT NULL,
    candidate_name  text              NOT NULL,
    score           DOUBLE PRECISION  NOT NULL,
    source          text              NOT NULL CHECK (source IN ('listenbrainz', 'musicbrainz_tag', 'user_cooccurrence')),
    fetched_at      timestamptz       NOT NULL DEFAULT now(),
    PRIMARY KEY (seed_artist_id, candidate_mbid, source)
);

CREATE INDEX artist_similarity_unmatched_seed_score_idx
    ON artist_similarity_unmatched (seed_artist_id, score DESC);