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.
Alan. 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 > > https://gist.github.com/3985764 > > 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?
