Approximate query counts for MySQL and Django.
When using MySQL, counting all rows is very expensive on large InnoDB tables. This is a replacement for QuerySet that returns an approximation if COUNT(*) is called with no additional constraints. In all other cases it should behave exactly as QuerySet.
This only works with MySQL and behaves normally for all other engines.
Install the package django-mysql-fuzzycount from PyPI using pip:
$ pip install -U django-mysql-fuzzycount
There are a couple ways to use the FuzzyCountQuerySet.
You can import and use the provided FuzzyCountManager on your Django models:
from django.db import models from mysql_fuzzycount.managers import FuzzyCountManager class Choice(model.Model): objects = FuzzyCountManager() # ...
Then, doing a count on the Choice model, without any constraints, will approximate the total count:
>>> Choice.objects.count() # approximation 100 >>> Choice.objects.filter(votes__gt=10).count() # not an approximation 28
Another common issue is counts in the admin for a model. There is a base ModelAdmin class that you can subclass in your admin.py files to prevent expensive COUNT(*) queries upon loading the admin page. In an admin.py for one of your models:
from django.contrib import admin from mysql_fuzzycount.admin import FuzzyCountModelAdmin from myapp.models import Choice class ChoiceAdmin(FuzzyCountModelAdmin): pass admin.site.register(Choice, ChoiceAdmin)
Now, when you load the admin page for the Choice model, the count for pagination will be approximate.
It has been tested in production, but there are no unit or integration tests.
Copyright © 2013, Educreations, Inc under the MIT LICENSE.
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