Github user twalthr commented on a diff in the pull request:
https://github.com/apache/flink/pull/5132#discussion_r159844472
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/TableEnvironment.scala
---
@@ -768,6 +768,39 @@ abstract class TableEnvironment(val config:
TableConfig) {
frameworkConfig
}
+ /**
+ * Reference input fields by name:
+ * All fields in the schema definition are referenced by name
+ * (and possibly renamed using an alias (as). In this mode, fields can
be reordered and
+ * projected out. Moreover, we can define proctime and rowtime
attributes at arbitrary
+ * positions using arbitrary names (except those that exist in the
result schema). This mode
+ * can be used for any input type, including POJOs.
+ *
+ * Reference input fields by position:
+ * Field references must refer to existing fields in the input type
(except for
+ * renaming with alias (as)). In this mode, fields are simply renamed.
Event-time attributes can
+ * replace the field on their position in the input data (if it is of
correct type) or be
+ * appended at the end. Proctime attributes must be appended at the
end. This mode can only be
+ * used if the input type has a defined field order (tuple, case class,
Row) and no of fields
+ * references a field of the input type.
+ */
+ protected def isReferenceByPosition(t: TypeInformation[_], fields:
Array[Expression]): Boolean = {
+ if (t.isInstanceOf[PojoTypeInfo[_]]) {
+ return false
+ }
+
+ val inputNames = t match {
+ case ct: CompositeType[_] => ct.getFieldNames
+ case _ => return false // atomic types are references by name
+ }
+
+ // use the by position mode if no of the fields exists in the input
+ fields.forall {
+ case UnresolvedFieldReference(name) => !inputNames.contains(name)
--- End diff --
Yes, that was my main concern behind this. This makes the difference
between by-ref and by-pos more explicit. In this case I think it is better to
fail instead of having implicit behavior that a user might not have intended. I
will add a comment about this in the code.
---
