Github user StephanEwen commented on the pull request:
https://github.com/apache/flink/pull/1115#issuecomment-141041498
You are right, in those drivers, it is handled in the wrong way. Probably
an artifact from the time before the `MultableObjectIterator` had both variants
of the `next()` method. It used to have only the reusing variant.
Clearly, this should be fixed.
Here is the guide that I try to follow when working with the mutable
objects:
- All `MultableObjectIterator`s have two variants of the `next()` method
- one for reuse, one without.
- The variant without reuse it crucial, as not every situation can work
with object reuse.
- The variant with reuse is optional, but should be implemented where
possible for performance.
- The task drivers (AllReduceDriver, ...) or algorithms (sorter / hasher)
know whether they want to work with reuse or not, and call the respective
method in that case.
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