Hi Guys, Thanku for your valuable suggestion. I see this works fine in cases were key values are unique.
In my use cases the values are as follows: *<bookid>,<eid>,<rating>* 0000012742,3244,1 0028604164,2344,3 0062059017,2344,5 0075546701,2344,1 0130213268,2344,8 0140105425,5675,3 0141304286,5677,6 0195052668,3453,8 0198775024,2342,9 0000012742,2346,2 0028604164,9789,4 0062059017,2346,3 0075546701,2345,2 0130213268,8907,4 0140105425,5675,5 0141304286,3457,6 0195052668,5678,7 0198775024,8975,8 0000012742,6798,3 0028604164,5434,7 0062059017,9754,4 0075546701,7890,6 0130213268,7655,7 0140105425,7564,8 0141304286,8433,3 0195052668,3252,6 0198775024,7765,7 My goal here to right a program which will output the books id's sorted ( ascending) by the average of rating. I am done till the following steps: 1. Map : create pairs key, value and context.write(key,value) 2. Reducer: For each key sum of ratings/no of book entries. context(key,avg_rating) Example output will be like: 0075546701,4.6v 0062059017,2.1 0195052668,6.1 0198775024,2.7 My next step is to sort the books ids based on (ascending) order of the average rating. How to write the program for getting the example output as follows: 0062059017,2.1 0198775024,2.7 0075546701,4.6 0195052668,6.1 Please let me know if my approach is wrong as i am new to hadoop. Thanks in advance, --Shashi. On Wed, Sep 14, 2011 at 11:32 AM, Sudharsan Sampath <sudha...@gmail.com>wrote: > One way is to reverse the <key,value> output in the mapper to emit<1, > 10050> and in the reducer, use a treeset to order ur values.. for each value > o/p <value, key> in the reducer. > > With this O/P will be sorted as per ur needs within each reducer. If u need > a total sorted o/p, u can use a single reducer or design ur partition logic > accordingly. > > Thanks > Sudhan S > > > On Wed, Sep 14, 2011 at 6:14 AM, ksgupta misc <ksgupta.m...@gmail.com>wrote: > >> Hi, >> >> I have the content like >> *10103*,1042279,*4* >> *10070*,1001089,*5* >> *10102*,1015504,*7* >> *10080*,1024369,*7* >> *10050*,1025671,*1* >> ... >> from which i separated the key,value pairs and got the output after a >> single map and reduce as follows: >> >> 10050 1 >> 10070 5 >> 10080 7 >> 10102 7 >> 10103 4 >> ... >> >> I require to sort the output<key,value> pair by value (In ascending >> order). >> Please let me know how can i go ahead. >> >> Required output: >> 10050 1 >> 10103 4 >> 10070 5 >> 10080 7 >> 10102 7 >> >> Thanks in advance, >> --Shashi >> >> >> >> >> >
