Github user aljoscha commented on a diff in the pull request:
https://github.com/apache/flink/pull/747#discussion_r33129956
--- Diff:
flink-staging/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/api/datastream/DataStream.java
---
@@ -301,16 +301,68 @@ public ExecutionConfig getExecutionConfig() {
}
/**
- * Groups the elements of a {@link DataStream} by the given key
positions to
- * be used with grouped operators like
- * {@link GroupedDataStream#reduce(ReduceFunction)}</p> This operator
also
- * affects the partitioning of the stream, by forcing values with the
same
- * key to go to the same processing instance.
*
+ * It creates a new {@link KeyedDataStream} that uses the provided key
for partitioning
+ * its operator states. Mind that keyBy does not affect the
partitioning of the {@link DataStream}
--- End diff --
But it seems to affect the partitioning of the stream since the constructor
of KeyedDataStream calls partitionByHash() on the DataStream. (This also
applied to the other keyBy() methods)
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