src/main/java/com/googlecode/objectify/impl/QueryEngine.java
public <T> QueryResults<Key<T>> queryKeysOnly(final KeyQuery query) {
		log.trace("Starting keys-only query");

		return new KeyQueryResults<>(ds.run(query));
	}
public <T> QueryResults<Key<T>> queryKeysOnly(final KeyQuery query) {
		log.trace("Starting keys-only query");

		return new KeyQueryResults<>(ds.run(query));
	}
Perform a keys-only query.