https://github.com/stephenmcd/django-postgres-fuzzycount

Fast / fuzzy PostgreSQL counts for Django
https://github.com/stephenmcd/django-postgres-fuzzycount

Last synced: 6 days ago
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Fast / fuzzy PostgreSQL counts for Django

• Host: GitHub
• URL: https://github.com/stephenmcd/django-postgres-fuzzycount
• Owner: stephenmcd
• License: bsd-2-clause
• Created: 2013-07-07T02:13:53.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2023-01-06T18:45:11.000Z (almost 2 years ago)
• Last Synced: 2024-10-14T00:13:42.944Z (21 days ago)
• Language: Python
• Homepage:
• Size: 12.7 KB
• Stars: 89
• Watchers: 5
• Forks: 12
• Open Issues: 3
• Metadata Files:
  • Readme: README.rst
  • License: LICENSE

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README

        
Created by `Stephen McDonald `_

Introduction

============

Up until PostgreSQL 9.2, ``COUNT`` queries generally required scanning

every row in a database table. With millions of rows, this can become

quite slow. One work-around for this is to query statistics in

PostgreSQL for an approximate row count, which in many cases is an

acceptable trade-off.

Given a table called ``bigdata``, the following query will return an

approximate row count::

    SELECT reltuples FROM pg_class WHERE relname = 'bigdata';

You can read more information about `slow COUNT queries in PostgreSQL`_

in the PostgreSQL wiki.

What ``django-postgres-fuzzycount`` provides is a way of using this

approach directly in your Django model managers. It was originally

built for displaying statistics in the `kouio RSS reader`_, a popular alternative to Google Reader, that acquired over 5 million news articles

in its database during the first week of its launch.

Installation

============

The easiest way to install ``django-postgres-fuzzycount`` is directly

from PyPi using `pip`_ by running the following command::

    $ pip install -U django-postgres-fuzzycount

Otherwise you can download and install it directly from source::

    $ python setup.py install

Usage

=====

By using the ``fuzzycount.FuzzyCountManager`` on your Django models,

its ``count()`` method will return an approximate value when querying

PostgreSQL tables without any ``WHERE`` OR ``HAVING`` clauses::

    from django.db import models

    from fuzzycount import FuzzyCountManager

    class BigData(models.Model):

        big = models.BooleanField(default=True)

        data = models.TextField()

        objects = FuzzyCountManager()

    BigData.objects.count()  # Uses fuzzycount

    BigData.objects.filter(id__gt=9000).count()  # Doesn't use fuzzycount

The ``fuzzycount.FuzzyCountManager`` also checks the database engine

being used, and only applies the approximate count query when using

PostgreSQL, so other database backends can be used and will behave as

usual (for varying definitions of `usual`, depending on the database :-).

Inspiration

===========

  * `postgres_loose_table_counts`_, a Ruby gem providing the same

    approach for Rails

  * This `Django snippet`_, which bakes the approach into the admin

.. _`slow COUNT queries in PostgreSQL`: http://wiki.postgresql.org/wiki/Slow_Counting

.. _`kouio RSS reader`: https://kouio.com

.. _`pip`: http://www.pip-installer.org/

.. _`postgres_loose_table_counts`: https://github.com/goodfilms/postgres_loose_table_counts

.. _`Django snippet`: http://djangosnippets.org/snippets/2855/