Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3550#discussion_r106546899
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/nodes/datastream/DataStreamOverAggregate.scala
---
@@ -191,3 +287,31 @@ class DataStreamOverAggregate(
}
+object DataStreamProcTimeCase {
+ class ProcTimeTimestampExtractor
+ extends AssignerWithPunctuatedWatermarks[Row] {
+
+ override def checkAndGetNextWatermark(
+ lastElement: Row,
+ extractedTimestamp: Long): Watermark = {
+ null
+ }
+
+ override def extractTimestamp(
+ element: Row,
+ previousElementTimestamp: Long): Long = {
+ System.currentTimeMillis()
--- End diff --
`System.currentTimeMillis()` is not not strictly increasing. For instance
the time of a machine can be synced by a timeserver. So we should always
remember the last emitted timestamp and return the `max` of the last and the
current time.
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