Re: [infinispan-dev] Adding a Combiner

Response from Brent Douglas: Hi Vladimir, I'm not sure this is the same thing being discussed however if it is not I had intended to request this anyhow. When I looked into using infinispans's map reduce facility this is the the task I came up with: http://pastebin.com/7GGjVnVt I would prefer to specify it as: http://pastebin.com/HTSq3g66 I'm pretty sure this is the not intended use case but it distributes the creation of my reports which is what I want. It's not really a big deal for me as I can get around this limitation by creating a wrapper class such as in the first example but it would be nice if I did not have to. Is this a reasonable request? Also, and this is probably just wrong, when I use this I bundle up the task and execute it via JMS. Would it be reasonable to make Collator extend Serializable? Brent On 12-01-30 11:47 AM, Vladimir Blagojevic wrote: > Guys, > > I was looking at this again recently and I still do not understand how combiner could have different interface than Reducer! Hadoop forces a user to implement combiner as a Reducer http://developer.yahoo.com/hadoop/tutorial/module4.html#functionality and http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/mapred... In addition, the original paper does not mention any change of types. > > What we have admittedly done wrong is to apply Reducer on individual Mapper without checking if a reduce function is both commutative and associative! This can lead to problems: http://philippeadjiman.com/blog/2010/01/14/hadoop-tutorial-series-issue-4... > > So yes, I am all for adding Combiner (it should do the optional reducer per mapper we do automatically now) but I do not see why we have to change the interface! > > > Regards, > Vladimir > > > > > _______________________________________________ > infinispan-dev mailing list > > infinispan-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/infinispan-dev _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev