On 31 October 2011 13:37, Mathias Herberts <[email protected]>wrote:
> I don't know if it's a bug but I'd rather have the ability to set a > Combiner specific group comparator than to have the Combiner use the group > comparator set for the Reducer. > On Oct 31, 2011 9:21 PM, "Harsh J" <[email protected]> wrote: > Now I'm curious. Can you argue that there's a case where it makes a difference? Preferably one where it can't be trivially curried into the combiner? S. > > Shevek, > > > > The problem Mathias indicates here is that the Combiners do not utilize > > the Grouping Comparators. They only use the Sort Comparators. Is that > > probably a bug is what I wonder. > > > > On 31-Oct-2011, at 11:14 PM, Shevek wrote: > > > > > I like the ability to reuse a Java component for both sorting and > > grouping, > > > and to be honest, since the cases where one can do a comparison without > > > deserializing the raw bytes are relatively few and far between, I tend > to > > > use java's Comparator interface, and wrap it in some > > > infrastructure-specific adapter. I have a vague feeling that Hadoop > > > sometimes calls the byte interface and sometimes the object interface > > > anyway? ICBW, the way I've been writing code makes it irrelevant. > > > > > > Alternatively, I've misunderstood the (simpler) question, and the > answer > > is > > > to use the setGroupingComparatorClass() API. > > > > > > S. > > > > > > On 29 October 2011 04:35, Mathias Herberts <[email protected] > > >wrote: > > > > > >> Another point concerning the Combiners, > > >> > > >> the grouping is currently done using the RawComparator used for > > >> sorting the Mapper's output. Wouldn't it be useful to be able to set a > > >> custom CombinerGroupingComparatorClass? > > >> > > >> Mathias. > > >> > > > > >
