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https://issues.apache.org/jira/browse/FLINK-1622?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14355035#comment-14355035
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ASF GitHub Bot commented on FLINK-1622:
---------------------------------------
Github user mxm commented on a diff in the pull request:
https://github.com/apache/flink/pull/466#discussion_r26130398
--- Diff:
flink-java/src/main/java/org/apache/flink/api/java/operators/UnsortedGrouping.java
---
@@ -159,7 +159,23 @@ public UnsortedGrouping(DataSet<T> set, Keys<T> keys) {
return new GroupReduceOperator<T, R>(this, resultType,
dataSet.clean(reducer), Utils.getCallLocationName());
}
-
+
+ /**
+ * Applies a partial GroupReduce transformation on a grouped {@link
DataSet}.
+ * In contrast to the reduceGroup transformation, the GroupReduce
function is only called on each partition. Thus,
+ * partial solutions are likely to occur.
+ * @param reducer The ReduceFunction that is applied on the DataSet.
+ * @return A GroupReducePartial operator which represents the partially
reduced DataSet
+ */
+ public <R> GroupReducePartialOperator<T, R>
reduceGroupPartially(GroupReduceFunction<T, R> reducer) {
+ if (reducer == null) {
+ throw new NullPointerException("GroupReduce function
must not be null.");
+ }
+ TypeInformation<R> resultType =
TypeExtractor.getGroupReduceReturnTypes(reducer, this.getDataSet().getType());
+
+ return new GroupReducePartialOperator<T, R>(this, resultType,
dataSet.clean(reducer), Utils.getCallLocationName());
+ }
+
--- End diff --
See my answer above.
> Add GroupReducePartial Operator
> -------------------------------
>
> Key: FLINK-1622
> URL: https://issues.apache.org/jira/browse/FLINK-1622
> Project: Flink
> Issue Type: Sub-task
> Affects Versions: 0.9
> Reporter: Aljoscha Krettek
>
> This does what a Reduce or GroupReduce Operator does, except it is only
> performed on a local partition.
> This is also similar to an explicit combine that can output a type that is
> different from the input.
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