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https://issues.apache.org/jira/browse/FLINK-3179?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15204063#comment-15204063
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ASF GitHub Bot commented on FLINK-3179:
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GitHub user ramkrish86 opened a pull request:
https://github.com/apache/flink/pull/1822
FLINK-3179 - Adding just a log message
As suggested in the JIRA, just adding a log message indicating to add an
combiner function before the partition operator.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/ramkrish86/flink FLINK-3179_log
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/1822.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1822
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commit 79ca46e6855b1573e140bc19cdb7563d9d4f09d8
Author: ramkrishna <[email protected]>
Date: 2016-03-21T11:33:42Z
FLINK-3179 - Adding just a log message
----
> 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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