public ImmutableSet<String> getAllRoleIds() {
        // Use a MongoCollection query here to avoid the mongojack deserializing and object creation overhead
        final FindIterable<Document> docs = dbCollection.find().projection(Projections.include("_id"));

        return StreamSupport.stream(docs.spliterator(), false)
                .map(doc -> doc.get("_id", ObjectId.class).toHexString())
                .collect(ImmutableSet.toImmutableSet());
    }
@Test
    void getAllRoleIds() {
        assertThat(service.getAllRoleIds()).isEqualTo(ImmutableSet.of(
                "564c6707c8306e079f718980",
                "56701ac4c8302ff6bee2a65d",
                "5b17d7c63f3ab8204eea0589",
                "58dbaa158ae4923256dc6266",
                "564c6707c8306e079f71897f",
                "58dbaa158ae4923256dc6265",
                "59fc4b2b6e948411fadbd85d",
                "59fc4b2b6e948411fadbd85e",
                "5c2f6d3b3dd06601be176b85",
                "5c488b67e3f1420b4d9ae635",
                "5c488f1de3f14219be1cb9f6",
                "5d41bb973086a840541a3ed2",
                "5f1f0d2a6f58d7c052d49775",
                "5f1f0d2a6f58d7c052d49778",
                "5f1f0d2a6f58d7c052d4977b",
                "5f22792d6f58d7c0521edb23"
        ));
    }