Dimitry, Suppose the command is like (A on a , B on b1 and B on b2 , C on c) .. Then it requires storing the intermediate join of AB on to disk right?
Thanks On Wed, Feb 3, 2010 at 5:18 PM, Dmitriy Ryaboy <[email protected]> wrote: > if you explicitly join 3 or more relations with a single command ("d = > join a on id, b on id, c on id;"), a and b will be buffered for each > key, while c, the rightmost relation, will be streamed. > > This is on a per-reducer basis. There is of course a whole lot of IO > going on for getting from the Mappers to Reducers, but none of it is > the intermediate result of joining A to B. > > -Dmitriy > > On Tue, Feb 2, 2010 at 10:52 PM, bharath v > <[email protected]> wrote: > > Hi , > > > > I have a small doubt in how pig handles queries containing join of more > than > > 2 tables . > > > > Suppose we have 3 tables A,B,C .. and the plan is "((AB)C)" .. > > We can join A,B in a map reduce job and join the resultant table with > "C". I > > have a doubt whether the result of "AB" is stored to disk before joining > > with C or is it streamed directly to join with C (I dont know how , just > a > > guess) . > > > > Any help is appreciated , > > > > Thanks > > >
