Description
The ExtractKeyFn[0] used by the by[1] method of the PCollectionImpl is using the default scale factor for a MapFn (1.0). It should be using 1.0 + the scale factor of the wrapped MapFn, in order to be accurate.
[0]: https://github.com/apache/crunch/blob/master/crunch-core/src/main/java/org/apache/crunch/fn/ExtractKeyFn.java
[1]: https://github.com/apache/crunch/blob/master/crunch-core/src/main/java/org/apache/crunch/impl/dist/collect/PCollectionImpl.java#L270