| > It's not that learning SQL is hard. It's that people are inherently lazy. "Learn another thing on top of the thing it already took me a couple of years to learn? No thanks." And that's a big fat mistake. There are so many ways to shoot yourself in the foot with mongo such that simply knowing the language mongo uses for most of its queries while not actually knowing the particulars of how mongo uses that language… well that's just a road to a world of hurt. For example, when I first inherited a mongo deployment I noticed the queries were painfully slow. Ah hah says me, let's index some shit. Guess what? Creating an index on a running system with that version of mongo = segfault. After a bunch of hair pulling I got mongo up and running and got the data indexed. But the map reduce job was STILL running so slowly that we couldn't ingest data from a few tens of sensors in real time. So I made sure to set up queues locally on the sensors to buy myself some time. Even in my little test environment with nothing else hitting the mongo server, mongod was still completely unable to run its map reduce nonsense in a performant manner. Mongo wisdom was: shard it! wait for our magical aggregation framework! Here's the thing: working at a dinky startup we can't afford to throw hardware at it especially that early in the game. Sharding the damn thing would also bring in mongo's inflexible and somewhat magical and unreliable sharding doohickey. So I thought back to previous experience with time series data. BTDT with MySQL, you're just trading one awful lock (javascript vm) for another (auto increment). So I set up a test rig with postgres. Bam. I was able to ingest the data around 18x faster. And that's the thing. Mongo appeals to people who are comfortable with javascript and resistant to learning domain specific knowledge. All that appealing javascript goodness comes with a gigantic cost. If you're blindly following the path of least resistance you're in for a bad time. P.S. plv8 is a thing, and you can script postgres in javascript if you really wanted to. |