[marcosdumay]

What I don't get about those discussions is why people assume databases that can ONLY do map/reduce are a good thing? SQL is perfectly able to express map/reduce operations, and they main relational databases handle it almost as well as it's possible.

[robconery]

Completely agree here. Your live transactional system needs to export reportable data - this can come in the form of a DB backup/download (which I've done many times) so you can run queries locally or by pushing CSVs using a cron job.

You can use a SQL query for this or a simple map/reduce - either way my argument is to focus on transactional design that works best for your system - don't conflate reporting needs with your live system (i.e. BA queries).