nwangtw commented on a change in pull request #3099: Nwang/add streamlet
operator interfaces with grouping v2
URL: https://github.com/apache/incubator-heron/pull/3099#discussion_r232722206
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File path: heron/api/src/java/org/apache/heron/streamlet/Streamlet.java
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@@ -209,6 +209,15 @@
*/
<T> Streamlet<T> applyOperator(IStreamletOperator<R, T> operator);
+ /**
+ * Returns a new Streamlet by applying the operator on each element of this
streamlet.
+ * @param operator The operator to be applied
+ * @param grouper The grouper to be applied with the operator
+ * @param <T> The return type of the transform
+ * @return Streamlet containing the output of the operation
+ */
+ <T> Streamlet<T> applyOperator(IStreamletOperator<R, T> operator,
StreamGrouper grouper);
Review comment:
That is a good question. Some other operators might need it as well.
As @jerrypeng said before, the grouping strategy for most (even though I am
not sure about its most or some) operations are fixed, like .map doesn't need
grouping in general, reduce needs a field grouping or custom grouping. Having a
streamlet level setGrouper() could be convenient but it makes it less
straightforward and cause confusion (which is why I am hesitate about the
Builder API).
I am totally open to feedbacks and other options. Please feel free to
discuss.
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