CREATE TABLE "track_artists" (
	"track_id" uuid NOT NULL,
	"artist_id" uuid NOT NULL,
	"position" integer DEFAULT 0 NOT NULL,
	"role" text DEFAULT 'main' NOT NULL,
	CONSTRAINT "track_artists_track_id_artist_id_pk" PRIMARY KEY("track_id","artist_id")
);
--> statement-breakpoint
ALTER TABLE "track_artists" ADD CONSTRAINT "track_artists_track_id_tracks_id_fk" FOREIGN KEY ("track_id") REFERENCES "public"."tracks"("id") ON DELETE cascade ON UPDATE no action;--> statement-breakpoint
ALTER TABLE "track_artists" ADD CONSTRAINT "track_artists_artist_id_artists_id_fk" FOREIGN KEY ("artist_id") REFERENCES "public"."artists"("id") ON DELETE cascade ON UPDATE no action;--> statement-breakpoint
CREATE INDEX "track_artists_artist_idx" ON "track_artists" USING btree ("artist_id");--> statement-breakpoint
-- Backfill: make the existing single artist of each track a main credit.
INSERT INTO "track_artists" ("track_id", "artist_id", "position", "role")
SELECT "id", "artist_id", 0, 'main' FROM "tracks" WHERE "artist_id" IS NOT NULL;