private BitSetNode mergeNodes(BitSetNode leftNode, BitSetNode rightNode) {
    assert leftNode.getStart() < rightNode.getStart();
    leftNode.merge(rightNode);
    map.remove(rightNode.getStart());
    return leftNode;
  }
Merges {@code leftNode} & {@code rightNode} and updates the map.
hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/store/wal/ProcedureStoreTracker.java