= Backwards-incompatible changes =

As Django is still in pre-1.0 mode, we haven't yet committed to maintaining backwards compatibility in any APIs. Although we're keeping such changes to a minimum, Django developers should be acutely aware of these changes.

Of course, once we reach 1.0, we'll be strongly committed to backward compatibility.

This page lists all backwards-incompatible changes to Django since the 0.95 release. For changes prior to 0.95, see the OlderBackwardsIncompatibleChanges page.

== Table of Contents ==

Changes made after Django [source:/django/tags/releases/0.95 0.95]
 * August 2, 2006: [http://code.djangoproject.com/wiki/BackwardsIncompatibleChanges#Databaseconstraintnameschanged Database constraint names changed]
 * August 11, 2006: [http://code.djangoproject.com/wiki/BackwardsIncompatibleChanges#Backslashescapingchanged Backslash escaping changed]
 * September 27, 2006: [http://code.djangoproject.com/wiki/BackwardsIncompatibleChanges#RemovedENABLE_PSYCOsetting Removed ENABLE_PSYCO setting]
 * January 16, 2007: [http://code.djangoproject.com/wiki/BackwardsIncompatibleChanges#ChangedAdmin.manageroptiontomoreflexiblehook Changed Admin.manager option to more flexible hook]
 * January 28, 2007: [http://code.djangoproject.com/wiki/BackwardsIncompatibleChanges#Changedprepopulate_fromtobedefinedintheAdminclassnotdatabasefieldclasses Changed prepopulate_from to be defined in the Admin class, not database field classes]
 * February 25, 2007: [http://code.djangoproject.com/wiki/BackwardsIncompatibleChanges#Movedadmindocviewsintodjango.contrib.admindocs Moved admin doc views into django.contrib.admindocs]
 * March 14, 2007: [http://code.djangoproject.com/wiki/BackwardsIncompatibleChanges#EnforcingMySQLdbversion Enforcing MySQLdb version]

Changes made after Django [source:/django/tags/releases/0.96 0.96]

 * March 31, 2007: [http://code.djangoproject.com/wiki/BackwardsIncompatibleChanges#Changedspacelesstemplatetagtoremoveallspaces Changed 'spaceless' template tag to remove all spaces]

== Database constraint names changed ==

As of [3512], the format of the constraint names Django generates for foreign key references changed slightly. These names are only used sometimes, when it is not possible to put the reference directly on the affected column, so this is not always visible.

The effect of this change is that {{{manage.py reset app_name}}} and similar commands may generate SQL with invalid constraint names and thus generate an error when run against the database (the database server will complain about the constraint not existing). To fix this, you will need to tweak the output of {{{manage.py sqlreset app_name}}} to match the correct constraint names and pass the results to the database server manually.

== Backslash escaping changed ==

As of [3552], the Django database API now escapes backslashes given as query parameters. If you have any database API code that match backslashes, and it was working before (despite the broken escaping), you'll have to change your code to "unescape" the slashes one level.

For example, this used to work:

{{{
#!python
# Code that matches a single backslash
MyModel.objects.filter(text__contains='\\\\')
}}}

But it should be rewritten as this:

{{{
#!python
# Code that matches a single backslash
MyModel.objects.filter(text__contains='\\')
}}}

== Removed ENABLE_PSYCO setting ==

As of [3877], the {{{ENABLE_PSYCO}}} setting no longer exists. If your settings file includes {{{ENABLE_PSYCO}}}, nothing will break per se, but it just won't do anything. If you want to use [http://psyco.sourceforge.net/ Psyco] with Django, write some custom middleware that activates Psyco.

== Changed Admin.manager option to more flexible hook ==

As of [4342], the {{{manager}}} option to {{{class Admin}}} no longer exists. This option was undocumented, but we're mentioning the change here in case you used it. In favor of this option, {{{class Admin}}} may now define one of these methods:

  * {{{queryset()}}}
  * {{{queryset_add()}}}
  * {{{queryset_change()}}}

These give you much more flexibility.

Note that this change was made to the NewformsAdminBranch. (We initially called the new method {{{change_list_queryset}}}, but this was changed in [4584] to be more flexible.) The change will not be made to trunk until that branch is merged to trunk.

== Changed prepopulate_from to be defined in the Admin class, not database field classes ==

As of [4446], the {{{prepopulate_from}}} option to database fields no longer exists. It's been discontinued in favor of the new {{{prepopulated_fields}}} option on {{{class Admin}}}. The new {{{prepopulated_fields}}} option, if given, should be a dictionary mapping field names to lists/tuples of field names. Here's an example comparing old syntax and new syntax:

{{{
#!python

# OLD:
class MyModel(models.Model):
    first_name = models.CharField(maxlength=30)
    last_name = models.CharField(maxlength=30)
    slug = models.CharField(maxlength=60, prepopulate_from=('first_name', 'last_name'))

    class Admin:
        pass

# NEW:
class MyModel(models.Model):
    first_name = models.CharField(maxlength=30)
    last_name = models.CharField(maxlength=30)
    slug = models.CharField(maxlength=60)

    class Admin:
        prepopulated_fields = {'slug': ('first_name', 'last_name')}
}}}

Note that this change was made to the NewformsAdminBranch. The change will not be made to trunk until that branch is merged to trunk.

== Moved admin doc views into django.contrib.admindocs ==

As of [4585], the documentation views for the Django admin site were moved into a new package, {{{django.contrib.admindocs}}}.

The admin docs, which aren't documented very well, were located at {{{docs/}}} in the admin site. They're also linked-to by the "Documentation" link in the upper right of default admin templates.

Because we've moved the doc views, you now have to activate admin docs explicitly. Do this by adding the following line to your URLconf:

{{{
#!python
(r'^admin/doc/', include('django.contrib.admindocs.urls')),
}}}

Note that this change was made to the NewformsAdminBranch. The change will not be made to trunk until that branch is merged to trunk.

== Enforcing MySQLdb version ==

As of [4724], Django raises an error if you try to use the MySQL backend with a {{{MySQLdb}}} (MySQL Python module) version earlier than 1.2.1p2. There were significant, production-related bugs in earlier versions, so we have upgraded the minimum requirement.

In [4767], we added a {{{mysql_old}}} backend, which is identical to the {{{mysql}}} backend prior to the change in [4724]. You can use this backend if upgrading the {{{MySQLdb}}} module is not immediately possible. However, the {{{mysql_old}}} backend is deprecated, and  we will not continue developing it.

== Changed 'spaceless' template tag to remove all spaces ==

As of [4885], the {{{spaceless}}} template tag removes *all* spaces between HTML tags instead of preserving a single space.