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Import library that provides conditional aggregates in Django. The tests are removed as they conflict with the Django startup. The sources are https://github.com/henriquebastos/django-aggregate-if Licence is MIT (Bitbake rev: 016b416fd0eaeab648a588053a2ee1f41bc02a84) Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
157 lines
4.9 KiB
ReStructuredText
157 lines
4.9 KiB
ReStructuredText
Django Aggregate If: Condition aggregates for Django
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====================================================
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.. image:: https://travis-ci.org/henriquebastos/django-aggregate-if.png?branch=master
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:target: https://travis-ci.org/henriquebastos/django-aggregate-if
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:alt: Test Status
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.. image:: https://landscape.io/github/henriquebastos/django-aggregate-if/master/landscape.png
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:target: https://landscape.io/github/henriquebastos/django-aggregate-if/master
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:alt: Code Helth
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.. image:: https://pypip.in/v/django-aggregate-if/badge.png
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:target: https://crate.io/packages/django-aggregate-if/
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:alt: Latest PyPI version
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.. image:: https://pypip.in/d/django-aggregate-if/badge.png
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:target: https://crate.io/packages/django-aggregate-if/
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:alt: Number of PyPI downloads
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*Aggregate-if* adds conditional aggregates to Django.
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Conditional aggregates can help you reduce the ammount of queries to obtain
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aggregated information, like statistics for example.
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Imagine you have a model ``Offer`` like this one:
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.. code-block:: python
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class Offer(models.Model):
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sponsor = models.ForeignKey(User)
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price = models.DecimalField(max_digits=9, decimal_places=2)
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status = models.CharField(max_length=30)
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expire_at = models.DateField(null=True, blank=True)
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created_at = models.DateTimeField(auto_now_add=True)
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updated_at = models.DateTimeField(auto_now=True)
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OPEN = "OPEN"
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REVOKED = "REVOKED"
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PAID = "PAID"
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Let's say you want to know:
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#. How many offers exists in total;
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#. How many of them are OPEN, REVOKED or PAID;
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#. How much money was offered in total;
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#. How much money is in OPEN, REVOKED and PAID offers;
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To get these informations, you could query:
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.. code-block:: python
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from django.db.models import Count, Sum
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Offer.objects.count()
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Offer.objects.filter(status=Offer.OPEN).aggregate(Count('pk'))
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Offer.objects.filter(status=Offer.REVOKED).aggregate(Count('pk'))
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Offer.objects.filter(status=Offer.PAID).aggregate(Count('pk'))
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Offer.objects.aggregate(Sum('price'))
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Offer.objects.filter(status=Offer.OPEN).aggregate(Sum('price'))
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Offer.objects.filter(status=Offer.REVOKED).aggregate(Sum('price'))
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Offer.objects.filter(status=Offer.PAID).aggregate(Sum('price'))
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In this case, **8 queries** were needed to retrieve the desired information.
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With conditional aggregates you can get it all with only **1 query**:
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.. code-block:: python
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from django.db.models import Q
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from aggregate_if import Count, Sum
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Offer.objects.aggregate(
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pk__count=Count('pk'),
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pk__open__count=Count('pk', only=Q(status=Offer.OPEN)),
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pk__revoked__count=Count('pk', only=Q(status=Offer.REVOKED)),
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pk__paid__count=Count('pk', only=Q(status=Offer.PAID)),
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pk__sum=Sum('price'),
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pk__open__sum=Sum('price', only=Q(status=Offer.OPEN)),
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pk__revoked__sum=Sum('price'), only=Q(status=Offer.REVOKED)),
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pk__paid__sum=Sum('price'), only=Q(status=Offer.PAID))
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)
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Installation
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------------
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*Aggregate-if* works with Django 1.4, 1.5, 1.6 and 1.7.
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To install it, simply:
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.. code-block:: bash
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$ pip install django-aggregate-if
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Inspiration
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-----------
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There is a 5 years old `ticket 11305`_ that will (*hopefully*) implement this feature into
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Django 1.8.
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Using Django 1.6, I still wanted to avoid creating custom queries for very simple
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conditional aggregations. So I've cherry picked those ideas and others from the
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internet and built this library.
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This library uses the same API and tests proposed on `ticket 11305`_, so when the
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new feature is available you can easily replace ``django-aggregate-if``.
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Limitations
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-----------
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Conditions involving joins with aliases are not supported yet. If you want to
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help adding this feature, you're welcome to check the `first issue`_.
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Contributors
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------------
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* `Henrique Bastos <http://github.com/henriquebastos>`_
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* `Iuri de Silvio <https://github.com/iurisilvio>`_
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* `Hampus Stjernhav <https://github.com/champ>`_
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* `Bradley Martsberger <https://github.com/martsberger>`_
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* `Markus Bertheau <https://github.com/mbertheau>`_
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* `end0 <https://github.com/end0>`_
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* `Scott Sexton <https://github.com/scottsexton>`_
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* `Mauler <https://github.com/mauler>`_
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* `trbs <https://github.com/trbs>`_
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Changelog
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---------
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0.5
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- Support for Django 1.7
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0.4
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- Use tox to run tests.
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- Add support for Django 1.6.
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- Add support for Python3.
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- The ``only`` parameter now freely supports joins independent of the main query.
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- Adds support for alias relabeling permitting excludes and updates with aggregates filtered on remote foreign key relations.
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0.3.1
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- Fix quotation escaping.
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- Fix boolean casts on Postgres.
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0.2
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- Fix postgres issue with LIKE conditions.
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0.1
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- Initial release.
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License
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=======
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The MIT License.
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.. _ticket 11305: https://code.djangoproject.com/ticket/11305
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.. _first issue: https://github.com/henriquebastos/django-aggregate-if/issues/1
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