MongoDB's performance on aggregation queries

Question

After hearing so many good things about MongoDB\'s performance we decided to give Mongodb a try to solve a problem we have. I started by moving all the records we have in se

Answer 1

The idea is that you improve the performance of aggregation queries by using MapReduce on a sharded database that is distributed over multiple machines.

I did some comparisons of the performance of Mongo's Mapreduce with a group-by-select statement in Oracle on the same machine. I did find that Mongo was approximately 25 times slower. This means that I have to shard the data over at least 25 machines to get the same performance with Mongo as Oracle delivers on a single machine. I used a collection/table with approximately 14 million documents/rows.

Exporting the data from mongo via mongoexport.exe and using the exported data as an external table in Oracle and doing a group-by in Oracle was much faster than using Mongo's own MapReduce.