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Posted to mapreduce-user@hadoop.apache.org by Sudip Sinha <su...@gmail.com> on 2012/04/04 18:51:22 UTC

Does the combiner always work if specified?

Hi,

I've read that the combiner only works if it is specified AND the sort
memory buffer overflows in the mapper.
http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-user/201107.mbox/%3C374D8F3F-B8B1-499F-BEDB-BFEE3219010C@hortonworks.com%3E

But when I run a Hadoop streaming job in R using RHadoop, the combiner
always runs when specified. This is on a very small dataset.

Is this the desired behaviour?

Thanks,
Sudip Sinha