@Override
  public int hashCode() {
    return parts.hashCode();
  }
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