40 items tagged “orm”
2021
SQLModel. A new project by FastAPI creator Sebastián Ramírez: SQLModel builds on top of both SQLAlchemy and Sebastián’s Pydantic validation library to provide a new ORM that’s designed around Python 3’s optional typing. The real brilliance here is that a SQLModel subclass is simultaneously a valid SQLAlchemy ORM model AND a valid Pydantic validation model, saving on duplicate code by allowing the same class to be used both for form/API validation and for interacting with the database.
2019
PugSQL. Interesting new twist on a definitely-not-an-ORM library for Python. With PugSQL you define SQL queries in files, give them names and then load them into a module which allows you to execute them as Python methods with keyword arguments. You can mark statements as only returning a single row (or a single scalar value) with a comment at the top of their file.
2018
Sqorn (via) JavaScript library for building SQL queries that makes really smart usage of ES6 tagged template literals. The magic of tagged template literals is that they let you intercept and process interpolated values, making them ideally suited to escaping parameters in SQL queries. Sqorn takes that basic ability and layers on some really interesting API design to allow you to further compose queries.
Describing events in code (via) Phil Gyford built an online directory of every play, movie, gig and exhibition he has been to in the past 38 years using a combination of digital archaeology and saved ticket stubs. He built it using Django and published this piece extensively describing the process he went through to design the data model.
Building a combined stream of recent additions using the Django ORM
I’m a big believer in the importance of a “recent additions” feed. Any time you’re building an application that involves users adding and editing records it’s useful to have a page somewhere that shows the most recent objects that have been created across multiple different types of data.
[... 1,647 words]2017
Implementing faceted search with Django and PostgreSQL
I’ve added a faceted search engine to this blog, powered by PostgreSQL. It supports regular text search (proper search, not just SQL“like” queries), filter by tag, filter by date, filter by content type (entries vs blogmarks vs quotation) and any combination of the above. Some example searches:
[... 3,103 words]2010
Easier custom Model Manager Chaining. A neat solution to the problem of wanting to write a custom QuerySet method (.published() for example) which is also available on that model’s objects manager, without having to write much boilerplate.
On Django And Migrations. South author Andrew Godwin on the plans for migrations in Django. His excellent South migration library will be split in to two parts—one handling database abstraction, dependency resolution and history tracking and the other providing autodetection and the South user interface. The former will go in to Django proper, encouraging other migration libraries to share the same core abstractions.
Appending the request URL to SQL statements in Django. A clever frame-walking monkey-patch which pulls the most recent HttpRequest object out of the Python stack and adds the current request.path to each SQL query as an SQL comment, so you can see it in debugging tools such as slow query logs and the PostgreSQL “select * from pg_stat_activity” query.
Cache Machine: Automatic caching for your Django models. This is the third new ORM caching layer for Django I’ve seen in the past month! Cache Machine was developed for zamboni, the port of addons.mozilla.org to Django. Caching is enabled using a model mixin class (to hook up some post_delete hooks) and a custom caching manager. Invalidation works by maintaining a “flush list” of dependent cache entries for each object—this is currently stored in memcached and hence has potential race conditions, but a comment in the source code suggests that this could be solved by moving to redis.
Announcing django-cachebot. The ORM caching space around Django is heating up. django-cachebot is used in production at mingle.com and takes a more low level approach to cache invalidation than Johnny Cache, enabling you to specifically mark the querysets you wish to cache and providing some advanced options for cache invalidation. Unfortunately it currently relies on a patch to Django core to enable its own manager.
Johnny Cache. Clever twist on ORM-level caching for Django. Johnny Cache (great name) monkey-patches Django’s QuerySet classes and caches the result of every single SELECT query in memcached with an infinite expiry time. The cache key includes a “generation” ID for each dependent database table, and the generation is changed every single time a table is updated. For apps with infrequent writes, this strategy should work really well—but if a popular table is being updated constantly the cache will be all but useless. Impressively, the system is transaction-aware—cache entries created during a transaction are held in local memory and only pushed to memcached should the transaction complete successfully.
2009
django-batch-select (via) A smart attempt at solving select_related for many-to-many relationships in Django. Add a custom manager to your model and call e.g. Entry.objects.all()[:10].batch_select(“tags”) to execute two queries—one pulling back the first ten entries and another using an “IN” query against the tags table to pull back all of the tags for those entries in one go.
Django 1.2 planned features.
The votes are in and the plan for Django 1.2 has taken shape - features are split in to high, medium and low priority. There's some really exciting stuff in there - outside of the things I've already talked about, I'm particularly excited about multidb, Model.objects.raw(SQL), the smarter {% if %} tag and class-based generic views.
Django 1.1 release notes (via) Django 1.1 is out! Congratulations everyone who worked on this, it’s a fantastic release. New features include aggregate support in the ORM, proxy models, deferred fields and some really nice admin improvements. Oh, and the testing framework is now up to 10 times thanks to smart use of transactions.
South’s Design. Andrew Godwin explains why South resorts to parsing your models.py file in order to construct information about for creating automatic migrations.
Haystack (via) A brand new modular search plugin for Django, by Daniel Lindsley. The interface is modelled after the Django ORM (complete with declarative classes for defining your search schema) and it ships with backends for both Solr and pure-python Whoosh, with more on the way. Excellent documentation.
Southerly Breezes. Andrew Godwin is slowly assimilating the best ideas from other Django migration systems in to South—the latest additions include ORM Freezing from Migratory and automatic change detection. Exciting stuff.
DB2 support for Django is coming. From IBM, under the Apache 2.0 License. I’m not sure if this makes it hard to bundle it with the rest of Django, which uses the BSD license.
2008
Secrets of the Django ORM. An undocumented (and unsupported) method of poking a Django QuerySet’s internal query to add group_by and having clauses to a SQL query.
Django 1.0 alpha release notes. The big features are newforms-admin, unicode everywhere, the queryset-refactor ORM improvements and auto-escaping in templates.
jQuery style chaining with the Django ORM
Django’s ORM is, in my opinion, the unsung gem of the framework. For the subset of SQL that’s used in most web applications it’s very hard to beat. It’s a beautiful piece of API design, and I tip my hat to the people who designed and built it.
[... 820 words]Queryset-refactor branch has been merged into trunk. Malcolm’s latest Django masterpiece is complete.
mysql_cluster (via) My Russian isn’t all that good, but this looks like a neat way of getting Django to talk to a master/slave setup, written by Ivan Sagalaev. UPDATE: English docs are linked from the comments.
Queryset Implementation. Malcolm explains the work that has gone in to the queryset-refactor branch. Executive summary: Python’s ORM is probably a lot better at SQL than you are.
Caching Layer for Django ORM. Interesting extension to Django’s ORM that adds automatic caching of querysets and smart cache invalidation.
Announcing StaticGenerator for Django. Simple but powerful static file generator for Django applications—just tell it about your model instances and it will create an entire static site based on calling get_absolute_url() on each one. Uses signals to repopulate the cache when a model changes.
2007
Django Evolution. Really smart take on the problem of updating database tables to reflect changes to Django models. Code that automatically modifies your database tables can be pretty scary, but Evolution seems to hit the right balance.
Using the extra() QuerySet modifier in Django for WeGoEat. You can use select() on a QuerySet to obtain extra values using subqueries.
tranquil. Inspired take on the Django ORM to SQLAlchemy problem: lets you define your models with the Django ORM but use SQLAlchemy to run queries against them.