presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/metadata/ShardIterator.java/ShardIterator/fetchNodes
class ShardIterator:    private void fetchNodes()
    {
        for (RaptorNode node : dao.getNodes()) {
            nodeMap.put(node.getNodeId(), node.getNodeIdentifier());
        }
    }