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Code Issues 32 Releases Wiki Activity

Fixed #13315, #13430 -- Recreated django.contrib.gis.db.backend module with SpatialBackend alias and added Adaptor alias for backwards-compatibility purposes; added GeoDjango 1.2 backwards-incompatibility documentation and release notes; added a section in the docs about how MySQL is a crippled spatial database; updated versions in install docs.

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git-svn-id: http://code.djangoproject.com/svn/django/trunk@13097 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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Justin Bronn
2010-05-04 21:43:40 +00:00
parent 41ccfa15d7
commit 402f8cede5
12 changed files with 226 additions and 26 deletions
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55
docs/ref/contrib/gis/db-api.txt
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@@ -23,13 +23,16 @@ its functionality into full-fledged spatial database backends:
* :mod:`django.contrib.gis.db.backends.oracle`
* :mod:`django.contrib.gis.db.backends.spatialite`
Backwards-Compatibility
-----------------------
Database Settings Backwards-Compatibility
-----------------------------------------
For those using the old database settings (e.g., the ``DATABASE_*`` settings)
Django 1.2 will automatically use the appropriate spatial backend as long
as :mod:`django.contrib.gis` is in your :setting:`INSTALLED_APPS`. For
example, if you have the following in your settings::
In :ref:`Django 1.2 <releases-1.2>`, the way
to :ref:`specify databases <specifying-databases>` in your settings was changed.
The old database settings format (e.g., the ``DATABASE_*`` settings)
is backwards compatible with GeoDjango, and will automatically use the
appropriate spatial backend as long as :mod:`django.contrib.gis` is in
your :setting:`INSTALLED_APPS`. For example, if you have the following in
your settings::
DATABASE_ENGINE='postgresql_psycopg2'
@@ -41,9 +44,37 @@ example, if you have the following in your settings::
...
)
Then, :mod:`django.contrib.gis.db.backends.postgis` will automatically be used as your
Then, :mod:`django.contrib.gis.db.backends.postgis` is automatically used as your
spatial backend.
.. _mysql-spatial-limitations:
MySQL Spatial Limitations
-------------------------
MySQL's spatial extensions only support bounding box operations
(what MySQL calls minimum bounding rectangles, or MBR). Specifically,
`MySQL does not conform to the OGC standard <http://dev.mysql.com/doc/refman/5.1/en/functions-that-test-spatial-relationships-between-geometries.html>`_:
Currently, MySQL does not implement these functions
[``Contains``, ``Crosses``, ``Disjoint``, ``Intersects``, ``Overlaps``,
``Touches``, ``Within``]
according to the specification. Those that are implemented return
the same result as the corresponding MBR-based functions.
In other words, while spatial lookups such as :lookup:`contains <gis-contains>`
are available in GeoDjango when using MySQL, the results returned are really
equivalent to what would be returned when using :lookup:`bbcontains`
on a different spatial backend.
.. warning::
True spatial indexes (R-trees) are only supported with
MyISAM tables on MySQL. [#fnmysqlidx]_ In other words, when using
MySQL spatial extensions you have to choose between fast spatial
lookups and the integrity of your data -- MyISAM tables do
not support transactions or foreign key constraints.
Creating and Saving Geographic Models
=====================================
Here is an example of how to create a geometry object (assuming the ``Zipcode``
@@ -307,4 +338,12 @@ Method PostGIS Oracle SpatiaLite
.. [#fngeojson] *See* Howard Butler, Martin Daly, Allan Doyle, Tim Schaub, & Christopher Schmidt, `The GeoJSON Format Specification <http://geojson.org/geojson-spec.html>`_, Revision 1.0 (June 16, 2008).
.. [#fndistsphere14] *See* `PostGIS 1.4 documentation <http://postgis.refractions.net/documentation/manual-1.4/ST_Distance_Sphere.html>`_ on ``ST_distance_sphere``.
.. [#fndistsphere15] *See* `PostGIS 1.5 documentation <http://postgis.refractions.net/documentation/manual-1.5/ST_Distance_Sphere.html>`_ on ``ST_distance_sphere``.
.. [#] MySQL only supports bounding box operations (known as minimum bounding rectangles, or MBR, in MySQL). Thus, spatial lookups such as :lookup:`contains <gis-contains>` are really equivalent to :lookup:`bbcontains`.
.. [#fnmysqlidx] *See* `Creating Spatial Indexes <http://dev.mysql.com/doc/refman/5.1/en/creating-spatial-indexes.html>`_
in the MySQL 5.1 Reference Manual:
For MyISAM tables, ``SPATIAL INDEX`` creates an R-tree index. For storage
engines that support nonspatial indexing of spatial columns, the engine
creates a B-tree index. A B-tree index on spatial values will be useful
for exact-value lookups, but not for range scans.
.. [#] Refer :ref:`mysql-spatial-limitations` section for more details.