Cache Manager

I had a problem: too many fetches from the DB. So, how to reduce load on the database without major changes to the code? Cache Manager is the answer. I've managed to reduce number of DB hits as much as 80% in some cases (dictionaries, complex relations). It is using standard cache mechanisms. I'm using it with mathopd. This is a very simple solution, instead of standard Manager, put this in your model definition as: `objects = CacheManager()` Then everythere elase in the code instead of all() or get(...) call all_cached() or get_cached(). I've kept original methods intact, to have an dual access, when you really, really must have frest data from the DB, and you can't wait for cache to expire. This is much easier to work with, then manually getting fetched data from the cache.No change to your existing code 9except model) and voila! Additionally if you have some data, you would like to store with your serialized object (e.g. related data, dynamic dictionaries), you can do this in the model method '_init_instance_cache'). Drop me an email if you find this useful. :)

• cache
• model
• manager

Sun 11 Jul 2010 Read More

OwnerField

This is a little helper for associating an owner to a newly created object, in this case making the assumption that the current user is always the owner. It removes the necessity of adding a custom save hook to your model. get_current_user comes from this middleware trick to cache the current user: http://code.djangoproject.com/wiki/CookBookThreadlocalsAndUser

• model
• user
• field
• owner
• ownerfield

Sun 11 Jul 2010 Read More

Alternate method of autoloading Django models in ipython

This is a little improvement to the [idea](http://www.djangosnippets.org/snippets/540/) from sheats a few days ago. I like it over the previous solutions because it doesn't involve doing anything other than running `./manage.py shell` inside your project directory. You don't have to create any files anywhere or remember to call anything, and `ipython` still works fine outside of a Django project. Throw this code in `~/.ipython/ipy_user_conf.py` (`ipythonrc` has apparently been deprecated).

• django
• model
• manage.py
• shell
• ipython

Sun 11 Jul 2010 Read More

Q marshaller

Django supports the serializing model objects, but does not support the serializing Q object like that, ============================ q = Q(username__contains="findme") model0.objects.filter(q) serialize(q) # X ============================ so I wrote a little marshaller for Q, this is example, ============================ from django.contrib.auth import models as django_models qs = django_query.Q(username__contains="spike") | django_query.Q(email__contains="spike") _m = QMarshaller() a = _m.dumps(qs) # a was serialized. When call the similiar queries in page by page, you don't need to write additional code for creating same Q(s) for filtering models, just use the serialized Q as http querystring and in the next page unserialize and apply it. That is simple life.

• model
• python
• q
• query

Sun 11 Jul 2010 Read More

Choices datatype for model

This class will automatically create a django choices tuple like this: STATUS_CHOICES = django_choices(Draft=1, Public=2, Closed=3) Additionally, it includes a method that converts the choices tuple to a dictionary. Like this: STATUS = STATUS_CHOICES.to_dict() Those types can come in handy when you need to use those magic values in your code. Best done within the model once so everyone can use it. Code based on: http://www.djangosnippets.org/snippets/455/. By the way, if you want to just have the method without having to convert to the newer syntax.. it's backward compatible. Just add django_choices in front of the first paren for your choices tuple.

• choices
• model

Sun 11 Jul 2010 Read More

Model manager with row caching

RowCacheManager is a model manager that will try to fetch any 'get' (i.e., single-row) requests from the cache. ModelWithCaching is an abstract base model that does some extra work that you'll probably want if you're using the RowCacheManager. So to use this code, you just need to do two things: First, set objects=RowCacheManager() in your model definition, then inherit from ModelWithCaching if you want the invalidation for free. If you are unusually brave, use the metaclass for ModelWithCaching and you won't even need the "objects=RowCacheManager()" line.

• get
• model
• manager
• model-inheritance
• caching

Sun 11 Jul 2010 Read More

ActiveManager: filter objects depending on publication and/or expiration dates

This manager is intended for use with models with publication and/or expiration dates. Objects will be retrieved only if their publication and/or expiration dates are within the current date. Use is very simple: class ExampleModel(models.Model): publish_date = models.DateTimeField() expire_date = models.DateTimeField(blank=True, null=True) objects = models.Manager() actives = ActiveManager(from_date='publish_date', to_date='expire_date') ExampleModel.actives.all() # retrieve active objects according to the current date The manager works correctly with nullable date fields. A null publication date means "*always published (until expiration date)*" and a null expiration date means "*never expires*". Most models should define the `objects` manager as the default manager, because otherwise out of date objects won't appear in the admin app.

• model
• manager
• active
• publication
• expiration
• date-filter

Sun 11 Jul 2010 Read More

HTML color code field

A CharField (Model) that checks that the value is a valid HTML color code (Hex triplet) like #FFEE00.

• model
• db
• color
• hexcode

Sun 11 Jul 2010 Read More

auto_now using signals

There has been some discussion about removing `auto_now` and `auto_now_add` some time ago. `auto_now_add` can be replaced be using a callable default value, `auto_now` can't. So I wrote this litte function for my current project (older ones still use `auto_add`) to fill the gap...but I'm not sure if `auto_now` will be removed at all.

• datetime
• model
• auto_now

Sun 11 Jul 2010 Read More

Custom Django manager that excludes subclasses

When you're using Django model inheritance, sometimes you want to be able to get objects of the base class that aren't instances of any of the subclasses. You might expect the obvious way of doing this, `SuperModel.objects.filter(submodel__isnull=True)`, to work, but unfortunately it doesn't. (Neither does `SuperModel.objects.filter(submodel__supermodel_ptr=None)`, or any other convoluted way I could think of doing it.) Here's a nicer approach for doing this. [The blog entry is here.](http://sciyoshi.com/blog/2008/aug/07/custom-django-manager-excludes-subclasses/)

• managers
• models
• model
• subclass
• manager
• inheritance
• subclasses

Sun 11 Jul 2010 Read More

SQL Function Decorator

This decorator will replace a method on a model with a class method that executes SQL in the functions doc string.

• sql
• model
• decorator

Sun 11 Jul 2010 Read More

get_model_or_404

Attempt to get a model from the `AppCache` and raise `Http404` if it cannot be found.

• shortcut
• model
• db
• helper

Sun 11 Jul 2010 Read More

MarkupTextField

I updated [MarkdownTextField](http://www.djangosnippets.org/snippets/882/) to have some choices in markup. It currently support for Markdown, Textile, Plain Text, and Plain HTML. It will add `%s_html` for the complied HTML and `%s_markup_choices` for a drop down of markup choices. Usage: class MyModel(models.Model): description = MarkupTextField()

• model
• markup
• markdown
• textile
• field

Sun 11 Jul 2010 Read More

Child aware model inheritance

Base models aren't aware of its inherited models, here is a quick solution to access child models from the base model.

• model
• inheritance
• child
• content-type

Sun 11 Jul 2010 Read More

uuid model field

This code provides a primary key field that is globally unique. It uses the pre_save method to auto-populate the field with a Universal Unique Id as the record is saved the first time.

• model
• field
• uuid
• universally-unique-identifier

Sun 11 Jul 2010 Read More