Github user StephanEwen commented on the pull request: https://github.com/apache/flink/pull/1616#issuecomment-182390682 I am very hesitant to introduce an "always copy" step in the data sources. Some data sources create Avro or Thrift types which are incredibly expensive to copy. I personally would prefer to accept that inconsistency at this point and make sure it is documented well (that source implementers should not emit the same internal elements multiple times). A user that wants to optimize the data source can actually check the object reuse config flag (the ExecutionConfig can be obtained from the RuntimeContext) and depending on that flag reuse objects differently in the code. What do you think?
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