When do I need map reduce for database queries?

MapReduce is needed for aggregations in MongoDB. The normal queries follow a very different (and much faster) code path and they should always be used for real-time operations. MapReduce is definitely not intended for real-time, it's more for batch jobs.

MapReduce is needed for aggregations in MongoDB. The normal queries follow a very different (and much faster) code path and they should always be used for real-time operations. MapReduce is definitely not intended for real-time, it's more for batch jobs.

Technically, you could write all your queries using MapReduce, but that would be both painful and slow.

Thanks for the explanation. I was kinda wondering about that as well, whether to use map-reduce for real-time processing because you won't notice this in development. – jpartogi Sep 19 '10 at 3:48 You said MapReduce would be PITA to write for every query.

Isn't that what you do in CouchDB? – never_had_a_name Sep 29 '10 at 0:48.

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