django-sequential-pagination 0.1.0
Fast sequential objects pagination for Django
License: BSD

django-sequential-pagination
============================

Paginate ordered Django querysets sequentially with "Next" button. Fully compatible with `django-el-pagination`_ (but doesn't depend on it).

The pagination is performed by object ID (or any other set of fields that give strict linear order) rather than by page number. Instead of ``?page=2``, ``?page=3``, etc., it produces links like ``?from=11``, ``?from=21`` and so on. This gives the following benefits:

* The pagination works extremely fast even on huge data sets. For example, on Postgres "normal" pagination may take seconds (or even minutes) on queries like ``?page=1000000``.

* It prevents duplicates on next page when new data is injected at top and shifts page boundaries (this is especially important for AJAX pagination).

The drawback is that there is no navigation to arbitrary page number and no reverse navigation, it's always only the link to "Next page" (or nothing at the last page).

.. _django-el-pagination: https://github.com/shtalinberg/django-el-pagination


Installation
============

::

        pip install django-sequential-pagination


Usage
=====

Add ``django_sequential_pagination`` to ``INSTALLED_APPS``:

.. code:: python

	# settings.py

	INSTALLED_APPS = [
		...
		'django_sequential_pagination',
	]


Pass an *ordered* queryset to the template:

.. code:: python

	# views.py
	
	def recent_posts(request):
		return render(request, "blog/posts.html", {
			'posts': Post.objects.all().order_by('-time', '-id'),
		})


Make sure that the ordering always has a tie breaker as the last key, otherwise you may get duplicates on page boundaries.

Now, paginate objects in the template:

.. code:: django

	{% load pagination %}

	{% paginate posts per_page=10 as page %}

	{% for post in page.objects %}
		<div>Post #{{ post.id }}</div>
	{% endfor %}

	{% if page.next_page_url %}
		<a href="{{ page.next_page_url }}">Next</a>
	{% endif %}


Settings
--------

You can override the default settings in your ``settings.py``:

.. code:: python

	SEQUENTIAL_PAGINATION_PER_PAGE = 20
	SEQUENTIAL_PAGINATION_KEY = 'from'  # querystring key to use, as in ?from=XXXX


django-el-pagination
--------------------

You can enable endless pagination with `django-el-pagination`_ by putting this in the page template:

.. _django-el-pagination: https://github.com/shtalinberg/django-el-pagination

.. code:: django

	{% paginate posts per_page=10 key='page' as page %}

	{% for post in page.objects %}
		<div>Post #{{ post.id }}</div>
	{% endfor %}

	{% if page.next_page_url %}
		<nav class="endless_container">
			<ul class="pagination"><!-- Bootstrap v3 styles -->
				<li>
					<a class="endless_more" href="{{ page.next_page_url }}" rel="{{ page.key }}">Show more</a>
				</li>
			</ul>
		</nav>
	{% endif %}

	<script>
		$.endlessPaginate({paginateOnScroll: true});
	</script>


Make sure the pagination ``key`` (or ``SEQUENTIAL_PAGINATION_KEY``) matches your ``AjaxListView.key``. The defaults are different (``from`` and ``page``, respectively).


Jinja2
------

If Jinja2 is installed, ``django_sequential_pagination.templatetags.pagination`` will be a ``jinja2.contextfunction``.

Additionally, if `django_jinja`_ is installed, it will be registered automatically as a global template function, so you can use it right away:

.. _django_jinja: https://github.com/niwinz/django-jinja

.. code:: jinja

	{% set page = paginate(posts, per_page=10) %}

	{% for post in page.objects %}
		<div>Post #{{ post.id }}</div>
	{% endfor %}

	{% if page.next_page_url %}
		<a href="{{ page.next_page_url }}">Next</a>
	{% endif %}