Stanley Xu 2012-10-31, 08:20
-Re: Is that possible to use Pig to do an optimized secondary sort.
Alan Gates 2012-10-31, 15:21
Seeing your Pig Latin script will help us determine whether this will work in your case. But in general Pig uses secondary sort when you do an order by in a nested foreach. So if you are grouping you could order within that group and then pass it to your UDF.
On Oct 31, 2012, at 1:20 AM, Stanley Xu wrote:
> Dear buddies,
> We are trying to write some of the UDF to do some machine learning work. We
> did a simple experiment to calculate the AUC through a UDF like the
> following code in gist
> The map-reduce job will only take a couple of few minutes, but will wait
> there hours to do the cleanup.
> I guess the reason is that the sort inside the foreach will generate lots
> of data spill to local fs and takes a long time to do cleanup there.
> In a java map-reduce problem, we could made it like a secondary sort. We
> make the model + ctr as the key so the same model's ctr will be sorted, and
> group by only the model name part, then the sort is done after shuffling.
> I am wondering if we could do that kind of optimization in pig as well?
Stanley Xu 2012-11-01, 05:03
Russell Jurney 2012-10-31, 15:55