Github user pnowojski commented on a diff in the pull request:
https://github.com/apache/flink/pull/6323#discussion_r202268969
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/sources/DefinedFieldMapping.scala
---
@@ -50,7 +50,8 @@ trait DefinedFieldMapping {
* type. It can also provide a mapping for fields which are not in the
[[TableSchema]] to make
* fields in the physical [[TypeInformation]] accessible for a
[[TimestampExtractor]].
*
- * @return A mapping from [[TableSchema]] fields to [[TypeInformation]]
fields.
+ * @return A mapping from [[TableSchema]] fields to [[TypeInformation]]
fields or
+ * null if no mapping is necessary.
*/
def getFieldMapping: JMap[String, String]
--- End diff --
annotate `Nullable` or change to `Optional`.
---
