Github user hequn8128 commented on a diff in the pull request:
https://github.com/apache/flink/pull/5327#discussion_r184993457
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/nodes/datastream/DataStreamRel.scala
---
@@ -53,4 +53,8 @@ trait DataStreamRel extends FlinkRelNode {
*/
def consumesRetractions: Boolean = false
+ /**
+ * Whether the [[DataStreamRel]] produces retraction messages.
+ */
+ def producesRetractions: Boolean = false
--- End diff --
A join generates retraction if it's type is left/right/full. It is
different from agg which generates retractions if
`sendsUpdatesAsRetraction(node) && node.producesUpdates` is true.
---
