Building a Toy Database: Concurrency is Hard
Building a Toy Database: Learning by Doing
Ever wondered how databases work under the hood? I decided to find out by building one from scratch. Meet Bazoola - a simple file-based database written in pure Python.
Why Build a Toy Database?
As a developer, I use relational databases every day, but I never truly understood what happens when I INSERT or SELECT. Building a database from scratch taught me more about data structures, file I/O, and system design than any tutorial ever could.
Plus, it's fun to implement something that seems like magic!
Read moreThe Cartesian Product Trap in Django ORM
I hit a performance wall at work recently after adding a single extra Count() on a Django queryset that looked harmless. Luckily, the problematic code didn't make it into the production environment, but I had to think hard to figure out what went wrong and find a solution.
The Hidden Cost of Test Inheritance
I'm subscribed to Adam Johnson's blog and usually really enjoy his writing - it's practical, deep, and no-bullshit. But one recent post, Python: sharing common tests in unittest, caught me off guard.
It describes a "neat" pattern: write reusable test logic in a base class, subclass it to test multiple objects, hiding the base class from unittest discovery. While the intent is fine - DRYing out duplicated test code - the result is fragile, confusing, and just not worth it.
Here's why.
Read moreWhy Django's override_settings Sometimes Fails (and How reload + patch Saved Me)
Sometimes @override_settings just doesn’t cut it.
I ran into a nasty issue while testing a Django module that relies on global state initialized during import. The usual test approach didn’t work. Here’s what happened and how I solved it.
Read moreCalculating the next run date of a Celery periodic task
Under the Hood of Spense.app: The Code.
While Spense v0.2 is under development, I want to talk about the internal organization of the application from a technical perspective. This article is mainly for web developers, and it's written in the corresponding language, so if you're reading and don't understand anything, that's okay, you can just skip it.
In a Nutshell
Backend on Django (Python), frontend on Django templates and Bootstrap, with a pinch of JavaScript and some htmx (not anymore).
Why So Boring?
Sounds not very hype, right. But remember that Spense in its current state is not a full-fledged product. It's more of a prototype, in which I often need to change things and test ideas. If the ideas work, I'll throw this code away and write another; if they don't, I'll just keep it for memory.
So, I chose Django not because I love it (actually, I hate it), but because I've gotten used to it over the last year, and it allows me to prototype the application easily and quickly.
Read moreGraphQL and Python
Docker Buildkit: the proper usage of --mount=type=cache
TL;DR The contents of directories mounted with
--mount=type=cacheare not stored in the docker image, so it makes sense to cache intermediate directories, rather than target ones.
In dockerfile:1.3 there is a feature of mounting file system directories during the build process, that can be used for caching downloaded packages or compilation artifacts.
For example, the uwsgi package must be compiled every time it is installed, and at first glance, build times can be reduced by making the entire Python package directory cacheable: