While trying out Flink 1.2, I found out that you can set a maxParallelism higher than 1 on a non-parallel operator.
I think we should have the same semantics as the setParallelism() method.
Also, when setting a global maxParallelism in the execution environment, it will be set as a default value for the non-parallel operator.
When restoring a savepoint from 1.1, you have to set the maxParallelism to the parallelism of the 1.1 job. Non-parallel operators will then also get the maxPar set to this value, leading to an error on restore.
So currently, users restoring from 1.1 to 1.2 have to manually set the maxParallelism to 1 for all non-parallel operators.