Simon Willison’s Weblog

37 items tagged “orm”

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. # 28th March 2018, 3:41 pm

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.

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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:

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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. # 20th July 2010, 6:21 pm

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. # 2nd June 2010, 4:27 pm

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. # 2nd June 2010, 9:09 am

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. # 11th March 2010, 7:35 pm

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. # 6th March 2010, 12:48 pm

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. # 28th February 2010, 10:55 pm

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. # 23rd November 2009, 4:19 pm

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. # 26th October 2009, 10:38 am

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. # 29th July 2009, 9:34 am

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. # 13th May 2009, 12:30 pm

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. # 17th April 2009, 9:53 pm

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. # 15th March 2009, 1:17 pm

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. # 18th February 2009, 10:58 pm

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. # 8th November 2008, 11:49 pm

Django 1.0 alpha release notes. The big features are newforms-admin, unicode everywhere, the queryset-refactor ORM improvements and auto-escaping in templates. # 22nd July 2008, 6:04 am

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.

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Queryset-refactor branch has been merged into trunk. Malcolm’s latest Django masterpiece is complete. # 27th April 2008, 7:21 am

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. # 21st March 2008, 8:45 am

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. # 19th March 2008, 9:43 am

Caching Layer for Django ORM. Interesting extension to Django’s ORM that adds automatic caching of querysets and smart cache invalidation. # 23rd January 2008, 3:18 pm

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. # 7th January 2008, 9:26 pm

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. # 23rd November 2007, 11:49 pm

Using the extra() QuerySet modifier in Django for WeGoEat. You can use select() on a QuerySet to obtain extra values using subqueries. # 24th October 2007, 7:28 pm

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. # 9th October 2007, 2:30 am

DbMigration—a schema migration tool for Django. Nice and simple tool for adding schema migrations to a Django application. # 27th September 2007, 3:04 pm

django-sphinx (via) More code from Curse Gaming; this time a really nice API for adding Sphinx full-text search to a Django model. # 9th September 2007, 12:35 am

AuditTrail. Add change tracking and history to a Django model with a single line of code. Doesn’t handle relationships though, which is definitely the toughest part of this problem. # 15th August 2007, 1 pm