A simple fix is to add another two attributes to JobConf class: mapOutputLeyClass and mapOutputValueClass. That allows the user to have different key/value classes for the intermediate and final outputs.
I'll file a bug for this problem. Runping -----Original Message----- From: Darek Zbik [mailto:[EMAIL PROTECTED] Sent: Friday, March 31, 2006 4:28 AM To: [email protected] Subject: Re: Different Key/Value classes for Map and Reduce? Runping Qi wrote: >When the reducers write the final results out, its output format is obtained >from the job object. By default, it is TextOutputFormat, and no conflicts. >However, if one wants to use SequencialFileFormat for the final results, >then the key/value classes are also obtained from the job object, the same >as the map tasks' output. Now we have a problem. It is impossible for the >map outputs and reducer outputs use different key/value classes, if one >wants the reducers generate outputs in SequentialFileFormat. > > > I have this problem in real situation. I solve it by creating my own output format which is in fact copy-paste of the SequentialFileFormat with small changes (simply a took output class from ohter (my own) job property). I think that each hadoop job shoud have posibility to denote output key/value from reduce task (eg. {set,get}ReducerOutput{Key,Value}). darek
