@Override
  public String toString() {
    if (isAnonymous()) {
      return toStringHelper(this)
          .addValue("anonymous")
          .addValue(format("x%08x", identityHashCode(this)))
          .toString();
    }
    return toStringHelper(this)
        .addValue(sourceNode.get().getClass().getSimpleName())
        .addValue(format("x%08x", identityHashCode(sourceNode.get())))
        .toString();
  }
Creates {@link RelationId} equal only to itself
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/analyzer/RelationId.java