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Pig, mail # user - What is the best way to do counting in pig?


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Re: What is the best way to do counting in pig?
Jonathan Coveney 2012-07-02, 21:31
group all uses a single reducer, but COUNT is algebraic, and as such, will
use combiners, so it is generally quite fast.

2012/7/2 Subir S <[EMAIL PROTECTED]>

> Group all - uses single reducer AFAIU. You can try to count per group
> and sum may be.
>
> You may also try with COUNT_STAR to include NULL fields.
>
> On 7/3/12, Sheng Guo <[EMAIL PROTECTED]> wrote:
> > Hi all,
> >
> > I used to use the following pig script to do the counting of the records.
> >
> > m_skill_group = group m_skills_filter by member_id;
> > grpd = group m_skill_group all;
> > cnt = foreach grpd generate COUNT(m_skill_group);
> >
> > cnt_filter = limit cnt 10;
> > dump cnt_filter;
> >
> >
> > but sometimes, when the records get larger, it takes lots of time and
> hang
> > up, and or die.
> > I thought counting should be simple enough, so what is the best way to
> do a
> > counting in pig?
> >
> > Thanks!
> >
> > Sheng
> >
>