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Hive, mail # user - Hive Group By Limitations


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Re: Hive Group By Limitations
John Meagher 2013-05-06, 18:34
"Not quite sure but I think each group by will give another M/R job."

It will be done in a single M/R job no matter how many fields are in
the GROUP BY clause.

On Mon, May 6, 2013 at 2:07 PM, Peter Chu <[EMAIL PROTECTED]> wrote:
> In Hive, I cannot perform a SELECT GROUP BY on fields not in the GROUP BY
> clause.
>
> Example: SELECT st.a, st.b, st.c, st.d, FROM some_table st GROUP BY st.a;
> -- This does not work.
>
> To make it work, I would need to add the other fields in the group by
> clause.
>
> Not quite sure but I think each group by will give another M/R job.
>
> Wondering if there is any other way / better way to do group by.
>
> Peter