private void pushChildren(N parent) {
    visitorStack.push(
        new VisitorStackEntry(
            createChildrenIterator(parent),
            visitorStack.isEmpty() ? 1 : visitorStack.peek().level + 1));
    ancestorStack.add(new AncestorStackEntry(parent, currentStateMatchInfo));
  }
This method must be invoked before iteration
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/schema/tree/AbstractTreeVisitor.java