MapReduce with MongoDB really, really slow (30 hours vs 20 minutes in MySQL for a equivalent database)

Question

I am doing now some data analyse tests and in the first, really simple I have got very strange results.

The idea is the following: from an internet access log (a col

Answer 1

I've actually answered this very similar question before. The limitations of Map Reduce in MongoDB have been outlined previously - as you mentioned, it is single threaded, it has to be converted to Java Script (spidermonkey) and back etc.

That is why there are other options:

1. The MongoDB Hadoop Connector (officially supported)
2. The Aggregation Framework (Requires 2.1+)

As of this writing the 2.2.0 stable release was not yet out, but it was up to RC2, so the release should be imminent. I would recommend giving it a shot as a more meaningful comparison for this type of testing.