@Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    DereferenceExpression that = (DereferenceExpression) o;
    return Objects.equals(base, that.base) && Objects.equals(field, that.field);
  }
If this DereferenceExpression looks like a QualifiedName, return QualifiedName. Otherwise
return null
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/DereferenceExpression.java