Does HBase MapReduce support a combiner stage? And if so, how?
Question
Hadoop map reduce supports a combiner stage. However, I can't find a similar capability in the HBase MapReduce package. Does it exist?
Solution
If you are running a MapReduce job with HBase as an input format and non-hbase output formats it is the same.
A combiner is a reducer that only operates on the output of a single mapper. As long as you only do things that are idempotent in your reducer, than you can put your reducer in the combiner slot by simply saying: job.setCombiner(.class);
OTHER TIPS
You can use job.setCombiner(.class); method to use combiner class in map reduce. Reducer will aslso acts as an combiner
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