A MongoDB Map/Reduce Job Explained
A real-world MongoDB map/reduce example used by the private group mailing lists tool Fiesta explained in detail. The only part I don’t agree with is emphasized below:
Map/Reduce is a great way to do aggregations and ETL-type operations with MongoDB.
Probably nitpicking, but MongoDB’s MapReduce—actually this applies to most NoSQL databases MapReduce implementations: CouchDB, Riak, etc.—can do only the transform part and very less so load[1] and no extract.
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One could argue that MongoDB’s
outoption can be seen as equivalent to the load phase, but we can agree that having the results replacing or merged in a collection is just a use case ↩
Original title and link: A MongoDB Map/Reduce Job Explained (©myNoSQL)
via: http://blog.fiesta.cc/post/10980328832/walkthrough-a-mongodb-map-reduce-job
