Sometimes when you're on a query-killing rampage to improve the performance of a page, you find yourself wondering exactly when various queries are triggered and executed. You know to add
selected_related, and all those goodies. Seeing every executed query isn't hard either.
Correctly mocking external entities in your unit tests is a bit tricky syntactically, and I have to look up the exact incantations to type every single time they're needed. Thus, I'll make a quick sales pitch about mocking, quickly explain it to the best of my current understanding, and end with a sequence of tricks to be updated as I learn more. In essence, it's my own personal cheat sheet, stored in an accessible location I'm unlikely to misplace.
Everyone knows about Django's
Q objects and how to chain them together for complex lookups. The syntax is straight forward.
results = MyModel.objects.filter(Q(key1="value1") | Q(key2="value2"))
That generates this unexciting SQL:
1 2 3
SELECT * FROM `my_table` WHERE (`my_table`.`key1` = "value1" OR `my_table`.`key2` = "value2")
But what happens when you have an unknown amount of filters?
The experience of sitting through a trailer and thinking, "Looks like I don't need to see that, now that every last plot twist was spoiled", or "New Comedy XYZ was pretty funny, but all the good parts were in the trailer," are too common.
As movies go, the only thing that approaches the awfulness of Jumper is having an otherwise good movie completely spoiled by a trailer that just wouldn't shut up.
At Stik.com, we're using Django to supply a RESTful interface to our database. Our support staff is also using its admin for simple ticket items. Fortunately for the business, but unfortunately for the Django admin, we have lots of tables with hundreds of millions of rows, and a few in the billions. We really didn't want to spend the time writing our own admin section for support staff, so the Django admin was a godsend... until we rolled it out to production and saw admin pages never respond ever. Read on to see what our problem was and how we fixed it.
Large tables in InnoDB may not be able to even render their
change_list view due to (possibly 2) expensive
COUNT(*) queries. With tables of 100M+ records, this can take 15+ minutes to complete, even on fast servers.
Unoriginally around these parts, my parents are Christian, all four of my grandparents were devout Christians, my aunts and uncles are Christian, my cousins are Christian, my... whatever else is Christian. All authentically, too. There aren't any phonies in the bunch. Thus, my falling away from not only Christianity, but any form of religion whatsoever, bucked several generations of family tradition.
The following is a how-to guide for surviving terrible situations that I wrote with two roommates, Dan Lindeman and Ross Lepine, back in undergrad in 2008 after watching 30 Days of Night. Without further adieu:
Up and running with Django, MySQL, Apache2, and EC2
Before we get started, I'm assuming you've mastered or completed the first part of the tutorial, your site code itself is complete, your virtual environment is functional in local development, and you have your domain name pointed the IP of the EC2 instance we just made. If any of these assumptions are false then you are probably getting ahead of yourself.
I've had the same debate at every company for which I've ever worked, and the setup is always the same. Legacy tools are in place that technically get the job done but the annoying, but newer programmers are calling for new methods and tools. Some of the older dogs and management don't want to change, citing the overhead and cost of switching gears -- while the voices of change insist that a smoother, faster, easier, and more stable iteration process awaits at the end of that overhead. On healthy teams this leads to a lot of passionate, respectful debate. On unhealthy teams it spawns gnashing of teeth, finger pointing, and name-calling.
First, allow me to make a few assumptions:
- You're running Mac OS X 10.8.
- You have MAMP 2.x installed (and this is preventing MySQL-python from installing).
- You're going to run your Django site within a virtualenv (If you weren't planning on doing this, now's a great time to change your mind!).
- You're tired of PHP and you want to use Django, but because of other projects are unable to remove MAMP and start fresh.
Why it's failing:
MySQL-python won't compile because it needs the MySQL headers which are not in the expected location under a MAMP install. Luckily, this isn't hard to remedy.