[Perf] MATERIALIZE my_follows CTE in GetTracks/GetPlaylists

api/dbv1/queries/get_playlists.sql

@@ -1,5 +1,6 @@
 -- name: GetPlaylists :many
-WITH my_follows AS (
+-- See get_tracks.sql for why my_follows is MATERIALIZED.
+WITH my_follows AS MATERIALIZED (
   SELECT
     followee_user_id as user_id,
     follower_count

api/dbv1/queries/get_tracks.sql

@@ -1,5 +1,9 @@
 -- name: GetTracks :many
-WITH my_follows AS (
+-- MATERIALIZED forces this CTE to compute once per call. Without it the
+-- planner inlines and re-evaluates the follows JOIN aggregate_user + sort
+-- once per row in the followee_reposts/favorites SubPlans, which dominates
+-- runtime for users with many follows.
+WITH my_follows AS MATERIALIZED (
   SELECT
     followee_user_id as user_id,
     follower_count

api/v1_track_test.go

@@ -24,6 +24,48 @@ func TestGetTrack(t *testing.T) {
 	})
 }
 
+// Regression coverage for the my_follows CTE in get_tracks.sql. The CTE
+// powers `has_current_user_*`, `followee_reposts`, and `followee_favorites`
+// and was changed to MATERIALIZED for performance — these assertions guard
+// against future refactors silently breaking the personalization shape.
+func TestGetTrackPersonalization(t *testing.T) {
+	app := testAppWithFixtures(t)
+	app.skipAuthCheck = true
+
+	var resp struct{ Data dbv1.Track }
+
+	// Track 200 (eYJyn) is reposted by user 1, who is followed by user 2 (ML51L).
+	// Track 100 (eYZmn) is saved by user 1.
+	// Querying as user 2 should populate followee_* with user 1, and current-user
+	// repost/save flags should be false.
+	_, body := testGet(t, app, "/v1/full/tracks/eYJyn?user_id=ML51L", &resp)
+	jsonAssert(t, body, map[string]any{
+		"data.id":                        "eYJyn",
+		"data.has_current_user_reposted": false,
+		"data.has_current_user_saved":    false,
+		"data.followee_reposts.0.user_id": trashid.MustEncodeHashID(1),
+	})
+
+	_, body = testGet(t, app, "/v1/full/tracks/eYZmn?user_id=ML51L", &resp)
+	jsonAssert(t, body, map[string]any{
+		"data.id":                          "eYZmn",
+		"data.has_current_user_reposted":   false,
+		"data.has_current_user_saved":      false,
+		"data.followee_favorites.0.user_id": trashid.MustEncodeHashID(1),
+	})
+
+	// Querying as user 1 themselves: their own repost/save shows on the flags;
+	// followee_* should not include themselves.
+	_, body = testGet(t, app, "/v1/full/tracks/eYJyn?user_id="+trashid.MustEncodeHashID(1), &resp)
+	jsonAssert(t, body, map[string]any{
+		"data.has_current_user_reposted": true,
+	})
+	_, body = testGet(t, app, "/v1/full/tracks/eYZmn?user_id="+trashid.MustEncodeHashID(1), &resp)
+	jsonAssert(t, body, map[string]any{
+		"data.has_current_user_saved": true,
+	})
+}
+
 func TestGetTrackFollowDownloadAcess(t *testing.T) {
 	app := testAppWithFixtures(t)
 	var trackResponse struct {