Github user sihuazhou commented on the issue:
https://github.com/apache/flink/pull/5934
About the serializer duplication problem, I think you are right,
duplicating a serialize is not always super cheap, so I think maybe the best
tradeoff is to not duplicate the serializer to save the performance cost, and
add some dedicated comments to describe why we don't duplicate it to making the
code more "defensive", what do you think?---
