mapreduce_开发者

java.lang.RuntimeException: java.lang.ClassNotFoundException when trying to run Jar job on Elastic MapReduce

What should I change to fix following error: I\'m trying to start a job on Elastic Mapreduce, and it crashes every time with message:[详细]

2023-04-04 04:18 分类：问答

How to set output writer in MapReduce

I\'m trying out the mapreduce framework from (http://code.google.com/p/appengine-mapreduce/) and modified the demo application a bit (use the mapreduce.input_readers.DatastoreInputReader instead of ma[详细]

2023-04-03 15:48 分类：问答

How to deal with unbalanced input of reduce task?

Recently I was asked how to deal with unbalanced input of reduce task. I thought for while and try to redistribute the data, but didn\'t come up with a goo开发者_运维知识库d solution. Any advice?Actua[详细]

2023-04-03 10:47 分类：问答

MapReduce aggregation based on attributes contained outside of document

Say I have a collection of \'activities\', each of which has a name, cost and location: {_id : 1 , name: \'swimming\', cost: \'3.40\', location: \'kirkstall\'}[详细]

2023-04-03 10:44 分类：问答

MongoDB map reduce producing different result to db.collection.find()

I have a map reduce like this: map: function() { emit(this.username, {sent:this.sent, received:this.received});[详细]

2023-04-03 09:36 分类：问答

How to start learning hadoop [closed]

Closed. This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this po[详细]

2023-04-03 08:39 分类：问答

Using mongoid with map reduce on an enslaved model favors one mongodb slave

I\'ve got 4 mongodb slaves off of a master,and running a map reduce frequently on data in an enslaved model seems to favor the first slave by a factor of 5开发者_如何学Gox.[详细]

2023-04-02 18:41 分类：问答

In mongo, how do I use map reduce to get a group by ordered by most recent

the map reduce examples I see use aggregation functions like count, but what 开发者_StackOverflowis the best way to get say the top 3 items in each category using map reduce.[详细]

2023-04-02 07:55 分类：问答

Why all the reduce tasks are ending up in a single machine?

I wrote a relatively simple map-reduce program in Hadoop platform (cloudera distribution). Each Map & Reduce write some diagnostic information to standard ouput besides the regular map-reduce task[详细]

2023-04-02 03:47 分类：问答

How to specify tab as a record separator for hadoop input text file?

The input file to my hadoop M/R job is a text file in which the records are separated by tab character \'\\t\' instead of newline \'\\n\'. How can I instruct hadoop to split using the tab character as[详细]

2023-04-01 23:32 分类：问答