Fabian Hueske created FLINK-3179:
------------------------------------
Summary: 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
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.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
