Not necessarily-- you can use a secondary sort to make a non-commutative aggregator deterministic. But we should have a warning to that effect.
J On Mon, Nov 12, 2012 at 10:12 AM, Matthias Friedrich <[email protected]> wrote: > Hi, > > I would guess that Aggregator implementations have to be associative > and commutative. Otherwise they can't be used in Combiners in a > deterministic way. Am I right? > > If this is the case I'd suggest we add a big fat warning to our > StringConcatAggregator, because string concatenation isn't > commutative. Or maybe even remove it from our core API because it's a > bad role model? > > Thanks, > Matthias >
