django-rest-framework-aggregates

Exposes aggregation features of the Django model queryset to the DRF API.

Requirements

• Python 3.6+
• Django 1.11+
• Django Rest Framework 3.5.3+

Overview

This renderer overwrites default behaviour for calls made to api v2 .agg endpoints.

Supports GET calls to list endpoints in the format:

endpoint.agg/?aggregate[Count]=(field to count)
endpoint.agg/?aggregate[Sum]=(field to sum)
endpoint.agg/?aggregate[custom_function]=arguments
endpoint.agg/?group_by[field to group by]&aggregate[Count]=id
endpoint.agg/?group_by[field to group by]&aggregate[Count]=id&aggregate[Sum]=(field to sum)

Supports date part extraction for aggregation:

endpoint.agg/?group_by[created__year]&aggregate[Count]=id

Supports choices to representation extract:

endpoint.agg/?group_by[choiceField]&aggregate[Count]=id

Support aggregating over multiple fields, either of

endpoint.agg/?aggregate[Sum]=id&aggregate[Sum]=number
endpoint.agg/?aggregate[Sum]=id,number

Custom Aggregations

The default aggregate functions supported are defined in django.db.models.aggregates.

Custom aggregate functions have been defined in drf_aggregates.aggregates

User defined aggregation are passed to a custom queryset manager calculate_aggregates as kwargs if defined.

Custom aggregate functions set on the queryset should return a dictionary of field names to aggregate functions, which will then be processed with the other aggregates.

Examples

Example setup can be found in the example/ folder.

To enable the renderer, update your Django settings file:

  REST_FRAMEWORK = {
      'DEFAULT_RENDERER_CLASSES': (
          'drf_aggregates.renderers.AggregateRenderer',
          ...
      ),
      ...
  }

In the Cars ViewSet we are outputting the result to json:

    def list(self, request, *args, **kwargs):
        queryset = self.filter_queryset(self.get_queryset())
        data = request.accepted_renderer.render({'queryset': queryset, 'request': request})
        return Response(data, content_type=f'application/json')

Tests

In order to run tests locally:

1. Install development requirements:

   pip3 install -r requirements-dev.txt

2. Update your environment to point to test Django settings file:

   export DJANGO_SETTINGS_MODULE=example.settings.test

3. Run tests:

   py.test