session: add ListSessionsByType method

And use it to replace one call to ListSessions which uses a filter
function which would be inefficient in SQL land.

session/interface.go

@@ -164,6 +164,9 @@ type Store interface {
 	// ListSessions returns all sessions currently known to the store.
 	ListSessions(filterFn func(s *Session) bool) ([]*Session, error)
 
+	// ListSessionsByType returns all sessions of the given type.
+	ListSessionsByType(t Type) ([]*Session, error)
+
 	// RevokeSession updates the state of the session with the given local
 	// public key to be revoked.
 	RevokeSession(*btcec.PublicKey) error

session/kvdb_store.go

@@ -371,6 +371,16 @@ func (db *BoltStore) ListSessions(filterFn func(s *Session) bool) ([]*Session, e
 	return db.listSessions(filterFn)
 }
 
+// ListSessionsByType returns all sessions currently known to the store that
+// have the given type.
+//
+// NOTE: this is part of the Store interface.
+func (db *BoltStore) ListSessionsByType(t Type) ([]*Session, error) {
+	return db.listSessions(func(s *Session) bool {
+		return s.Type == t
+	})
+}
+
 // listSessions returns all sessions currently known to the store that pass the
 // given filter function.
 func (db *BoltStore) listSessions(filterFn func(s *Session) bool) ([]*Session,

session/store_test.go

@@ -31,7 +31,7 @@ func TestBasicSessionStore(t *testing.T) {
 	clock.SetTime(testTime.Add(time.Second))
 	s2 := newSession(t, db, clock, "session 2")
 	clock.SetTime(testTime.Add(2 * time.Second))
-	s3 := newSession(t, db, clock, "session 3")
+	s3 := newSession(t, db, clock, "session 3", withType(TypeAutopilot))
 	clock.SetTime(testTime.Add(3 * time.Second))
 	s4 := newSession(t, db, clock, "session 4")
 
@@ -64,6 +64,22 @@ func TestBasicSessionStore(t *testing.T) {
 	assertEqualSessions(t, s2, sessions[1])
 	assertEqualSessions(t, s3, sessions[2])
 
+	// Test the ListSessionsByType method.
+	sessions, err = db.ListSessionsByType(TypeMacaroonAdmin)
+	require.NoError(t, err)
+	require.Equal(t, 2, len(sessions))
+	assertEqualSessions(t, s1, sessions[0])
+	assertEqualSessions(t, s2, sessions[1])
+
+	sessions, err = db.ListSessionsByType(TypeAutopilot)
+	require.NoError(t, err)
+	require.Equal(t, 1, len(sessions))
+	assertEqualSessions(t, s3, sessions[0])
+
+	sessions, err = db.ListSessionsByType(TypeMacaroonReadonly)
+	require.NoError(t, err)
+	require.Empty(t, sessions)
+
 	// Ensure that we can retrieve each session by both its local pub key
 	// and by its ID.
 	for _, s := range []*Session{s1, s2, s3} {
@@ -310,6 +326,12 @@ func withLinkedGroupID(groupID *ID) testSessionModifier {
 	}
 }
 
+func withType(t Type) testSessionModifier {
+	return func(s *Session) {
+		s.Type = t
+	}
+}
+
 func newSession(t *testing.T, db Store, clock clock.Clock, label string,
 	mods ...testSessionModifier) *Session {
 

session_rpcserver.go

@@ -1259,9 +1259,7 @@ func (s *sessionRpcServer) ListAutopilotSessions(_ context.Context,
 	_ *litrpc.ListAutopilotSessionsRequest) (
 	*litrpc.ListAutopilotSessionsResponse, error) {
 
-	sessions, err := s.cfg.db.ListSessions(func(s *session.Session) bool {
-		return s.Type == session.TypeAutopilot
-	})
+	sessions, err := s.cfg.db.ListSessionsByType(session.TypeAutopilot)
 	if err != nil {
 		return nil, fmt.Errorf("error fetching sessions: %v", err)
 	}