Stephan explained in that thread that we're picking the min watermark when doing operations that join streams from multiple sources. If we have m:n partition-source assignment where m>n, the source is going to end up with the max watermark. Having m<=n ensures that the lowest watermark is used.
Re: automatic enforcement, perhaps allowing for more than 1 Kafka partition on a source should require opt-in, e.g. allowOversubscription() -- View this message in context: http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Kafka-partition-alignment-for-event-time-tp4782p4788.html Sent from the Apache Flink User Mailing List archive. mailing list archive at Nabble.com.
