Let combiner use different comparator instead of OutputKeyComparator
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Key: HADOOP-5810
URL: https://issues.apache.org/jira/browse/HADOOP-5810
Project: Hadoop Core
Issue Type: Wish
Components: mapred
Affects Versions: 0.20.0, 0.19.1
Environment: hadoop 0.19, or 0.20
Reporter: schubert zhang
Priority: Minor
I have a dataset with map key="city+userid+time". The output of mapper are
sorted by this map key.
Than, I group the reduce output according to "city+userid" by define my
OutputValueGroupingComparator which just compare "city+userid" in the mapkey. I
still want the output are sorted by time in each group. It works fine.
But to improve the performance, I want to use combiner which should also group
as "city+userid", but sorted by "city+userid+time".
So, wish to develop a new feature to let combiner use different comparator
instead of OutputKeyComparator.
For example CombinerGroupingComparator?
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