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From Ted Dunning <>
Subject Re: Basic queries regarding Apache Drill working
Date Thu, 04 Apr 2013 13:27:20 GMT
On Thu, Apr 4, 2013 at 12:27 PM, devansh kumar <>wrote:

> Hi,
> I am new and am trying to understand how Apache Drill  works but i have a
> few queries.
> Can anyone help me understand these things?
> 1.
> I am trying to understand if the execution engine is going to break up the
> data.

Normally the data will already have been broken up across a cluster.

> What will happen if i am trying to an aggregation operation like (AVERAGE).
> How will that work??


> I have seen operations as SUM and COUNT.
> How will the Query execution tree look like in case of an AVERAGE

It will look exactly like a SUM or COUNT except that two numbers will be
accumulated instead of one.

> 2.
> Does the Resource model is optimized when compared to MapReduce.

Yes.  This will happen because multiple levels of aggregation can be done
in one tree without the barrier between map and reduce imposed by the
MapReduce structure.

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