does Hive implement any Combiner by default?

[Edson Ramiro]

hi all,

I'm executing TPC-H on Hive 2.0.1, using Yarn 2.7, and I'm wondering if
Hive implements any Combiner by default? If so, how do I enable it?

I am asking this because I checked the values of COMBINE_INPUT_RECORDS and
COMBINE_OUTPUT_RECORDS and they are always zero.

Thanks in advance,

      Edson Ramiro