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https://issues.apache.org/jira/browse/FLINK-3179?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15150383#comment-15150383
]
ASF GitHub Bot commented on FLINK-3179:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/1553#discussion_r53153472
--- Diff:
flink-tests/src/test/java/org/apache/flink/test/javaApiOperators/GroupReduceITCase.java
---
@@ -434,6 +431,95 @@ public void
testCorrectnessOfGroupreduceWithDescendingGroupSort() throws Excepti
}
@Test
+ public void
testCorrectnessOfGroupreduceWithExplicitPartitionOfReducer() throws Exception {
+ /*
+ * check correctness of groupReduce with descending group sort
+ */
+ final ExecutionEnvironment env =
ExecutionEnvironment.getExecutionEnvironment();
+ env.setParallelism(1);
+
+ DataSet<String> ds = CollectionDataSets.getStringDataSet(env);
+
+ DataSet<Tuple2<String, Integer>> counts =
+ // split up the lines in pairs (2-tuples) containing:
(word,1)
+ ds.flatMap(new Tokenizer()).partitionByHash(0)
+ // group by the tuple field "0" and sum up
tuple field "1"
+ .groupBy(0)
+ .sum(1);
+
+ List<Tuple2<String, Integer>> result = counts.collect();
+ String expected = "am,1\n"
+ +
+ "are,1\n" +
+ "comment,1\n" +
+ "fine,1\n" +
+ "hello,3\n" +
+ "hi,1\n"+
+ "how,1\n"+
+ "i,1\n"+
+ "lol,1\n"+
+ "luke,1\n"+
+ "random,1\n"+
+ "skywalker,1\n"+
+ "world,2\n"+
+ "you,1\n";
+
+ compareResultAsTuples(result, expected);
+ }
+
+ @Test
+ public void
testCorrectnessOfGroupreduceWithoutExplicitPartitionOfReducer() throws
Exception {
+ /*
+ * check correctness of groupReduce with descending group sort
+ */
+ final ExecutionEnvironment env =
ExecutionEnvironment.getExecutionEnvironment();
+ env.setParallelism(1);
--- End diff --
No parallelism of `1` and a custom `GroupReduceFunction` with
`GroupCombineFunction` interface.
> Combiner is not injected if Reduce or GroupReduce input is explicitly
> partitioned
> ---------------------------------------------------------------------------------
>
> Key: FLINK-3179
> URL: https://issues.apache.org/jira/browse/FLINK-3179
> Project: Flink
> Issue Type: Bug
> Components: Optimizer
> Affects Versions: 0.10.1
> Reporter: Fabian Hueske
> Assignee: ramkrishna.s.vasudevan
> Priority: Critical
> Fix For: 1.0.0, 0.10.2
>
>
> The optimizer does not inject a combiner if the input of a Reducer or
> GroupReducer is explicitly partitioned as in the following example
> {code}
> DataSet<Tuple2<String,Integer>> words = ...
> DataSet<Tuple2<String,Integer>> counts = words
> .partitionByHash(0)
> .groupBy(0)
> .sum(1);
> {code}
> Explicit partitioning can be useful to enforce partitioning on a subset of
> keys or to use a different partitioning method (custom or range partitioning).
> This issue should be fixed by changing the {{instantiate()}} methods of the
> {{ReduceProperties}} and {{GroupReduceWithCombineProperties}} classes such
> that a combine is injected in front of a {{PartitionPlanNode}} if it is the
> input of a Reduce or GroupReduce operator. This should only happen, if the
> Reducer is the only successor of the Partition operator.
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