It's nothing new that PostgreSQL is a great tool for doing analytics, even coming from MongoDB. I'm very happy that MongoDB took this route, it speaks a lot about their capabilities in the non-OLTP world.<p>Having said that, I very biasedly say that there's a much better solution to this connector, which doesn't flatten out the MongoDB data: it's called ToroDB (<a href="https://github.com/torodb/torodb" rel="nofollow">https://github.com/torodb/torodb</a>).<p>ToroDB, open source, speaks the MongoDB protocol, transforms documents to relational tables (without any kind of flattening, and without having to define any schema) and stores data in a RDBMS. More precisely, PostgreSQL.<p>Current development version (repl branch) speaks the replication protocol, and hence can replicate live from a MongoDB into PostgreSQL. No connector needed, no flattening, no FDWs, nothing else. Just add a new "slave" (ToroDB) to your replica set and you're good to go.<p>It goes even further: if you want pure data warehousing, ToroDB will soon support GreenPlum. Some initial benchmarks (<a href="http://www.slideshare.net/8kdata/torodb-scaling-postgresql-like-mongodb" rel="nofollow">http://www.slideshare.net/8kdata/torodb-scaling-postgresql-l...</a>, slide #42) show 25x-75x improvement between doing aggregate queries in MongoDB and their equivalent queries in GreenPlum's distributed SQL.<p>Now that MongoDB 3.2 ships with PostgreSQL "included", feel free to try ToroDB. It's always better the original :)<p>Note: I am a ToroDB developer.