@Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    return parts.equals(((QualifiedName) o).parts);
  }
For an identifier of the form "a.b.c.d", returns "a.b.c", For an identifier of the form "a",
returns absent
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/QualifiedName.java