TIL: DEBUG=True will eat all your memory
So, there I was synchronising several thousand database records with a 3rd party server. Off I go to take care of some serious business while I wait for the sync to complete. But when I return instead of seeing a nicely up-to-date database, my machine is thrashing so hard it's almost completely unresponsive. Turns out Python is eating up 80% of the memory.
So I pile into optimising the code that does the syncing. No luck there. (I mean, the code's better but Python still eats all the memory.) So I figure I better take a look at exactly what's taking up all that space. While looking for some memory profiling tools, I come across this post on debugging memory leaks in Django.
Note especially point #3:
Remember that if you have DEBUG = True, you will see an ever-increasing heap because of the queries being cached on the connection object.
Oh. I see. Yep, that fixes it. Python now consumes a mere 0.8% or the system memory, and all is well.