Filtering Django Querysets by Model Properties

Queries on Django models often employ standard filters to select specific instances based on predefined field values. However, what if you need to filter based on a custom property defined within your model?

Can You Filter Querysets by Model Properties?

Unfortunately, Django's filters primarily operate at the database level, translating them into SQL commands to efficiently retrieve data. These filters are not able to directly access Python properties defined within your model.

Why This Limitation Exists

Django's query evaluation framework is designed to optimize performance by performing database operations. Python properties, on the other hand, require Python execution to calculate their values. Mixing these two concepts would lead to inefficient and potentially error-prone queries.

Alternative Approach

To accommodate filtering based on custom properties, consider loading the model objects into Python and evaluating the properties manually. While this approach may be less efficient, it provides greater flexibility in filtering by model-specific logic or dynamically calculated values.

Example Usage

To filter by a model property, you can use the following approach:

# Load the model objects
my_models = MyModel.objects.all()

# Filter based on the property
filtered_models = [model for model in my_models if model.myproperty == [..]]

Remember that this method involves retrieving all model instances into Python and later filtering them, which can become less efficient for large datasets.