reticool/django-materialized-views

A simple Django framework for managing materialized views.

======================================================================= django-materialized-views - A simple Django materialized view framework

Overview

This implements a simple interface and management command for updating and maintaining cached or calculated tables in small batches.

Usage

To use, subclass the parent class and override the 6 methods for detecting and performing insert, update and deletions, e.g.

from django_materialized_views.models import MaterializedView

class MyModel(models.Model, MaterializedView):

    key = models.CharField(max_length=100, db_index=True, unique=True)
    
    cached_value = models.CharField(max_length=100, db_index=True)
    
    @classmethod
    def needs_insert(cls):
        # This returns true if there are new materialized records we need to create.
        return MyOtherTable.objects.exclude(value__in=cls.objects.all().values_list('cached_value').count()

    @classmethod
    def needs_update(cls):
        # This returns true if there are new materialized records we need to update.
        return MyOtherTable.objects.filter(some_criteria_date__gt=date.today()-timedelta(days=7)).count()
        
    @classmethod
    def needs_delete(cls):
        # This returns true if there are new materialized records we need to delete.
        return MyOtherTable.objects.filter(deleted__isnull=False).count()
    
    @classmethod
    def do_insert(cls):
        for r in MyOtherTable.objects.get_new():
            cls.objects.create(key=r.key, cached_value=r.value)

    @classmethod
    def do_update(cls):
        for r in MyOtherTable.objects.get_updated():
            obj, _ = cls.objects.get_or_create(key=r.key, cached_value=r.value)
            obj.cached_value = r.value
            obj.save()

    @classmethod
    def do_delete(cls):
        cls.objects.filter(key__in=MyOtherTable.objects.get_obsolete().values_list('key')).delete()

Then schedule the management command update_materialized_views, via cron or similar scheduler, to run as often as you'd like the materialized view to be updated.

By default, this will update all subclasses of MaterializedView, but you can specify a specific subclass using the --models parameter.