hive-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Jonathan Coveney <jcove...@gmail.com>
Subject Re: Is there a reason why this simple query would take a very long time?
Date Mon, 24 Jan 2011 22:01:06 GMT
Yes, I tried that, it looks like it forces it to 1 if there are no groups.

2011/1/24 Ajo Fod <ajo.fod@gmail.com>

> oh ... sorry  you say you already tried that.
>
>
>
> On Mon, Jan 24, 2011 at 1:54 PM, Ajo Fod <ajo.fod@gmail.com> wrote:
> > you could try to set the number of reducers e.g:
> > set mapred.reduce.tasks=4;
> >
> > set this before doing the select.
> >
> > -Ajo
> >
> > On Mon, Jan 24, 2011 at 1:13 PM, Jonathan Coveney <jcoveney@gmail.com>
> wrote:
> >> I have a 10 node server or so, and have been mainly using pig on it, but
> >> would like to try out Hive.
> >> I am running this query, which doesn't take too long in Pig, but is
> taking
> >> quite a long time in Hive.
> >>
> >> hive -e "select count(1) as ct from my_table where v1='02' and v2 =
> >> 11112222;" > thecount
> >> One thing is that this job only uses 1 reducer, but it is taking most of
> its
> >> time in its reduce step. I tried manually setting more reducers, but I
> think
> >> that for a job without groups, it forces 1 reducer?
> >> Either way, would love to know why this is dragging? It's worth noting
> that
> >> my_table is not saved in the Hive format, but rather as a flat file. I
> >> realize that this can influence performance, but shouldn't it at least
> >> perform on par with pig?
> >> Thanks for your help
> >> Jon
> >
>

Mime
View raw message