Using Admin Sortable¶
This Django module offers three mixin classes to be added to the existing classes of your model admin:
They slightly modify the admin views of a sortable model. There is no need to derive your model class from a special base model class. You can use your existing ordered field, just as you always did, or add a new one with any name you like, if needed.
Integrate your models¶
Each database model which shall be sortable, requires a position value in its model description. Rather than defining a base class, which contains such a positional value in a hard coded field, this module lets you reuse existing sort fields or define a new field for the sort value.
Therefore this module can be applied in situations where your model is derived from an existing abstract model which already contains any kind of position value. The only requirement for this module is, that this position value be specified as the primary field used for sorting. This in Django is declared through the model’s Meta class. An example models.py:
class SortableBook(models.Model): title = models.CharField('Title', null=True, blank=True, max_length=255) my_order = models.PositiveIntegerField(default=0, blank=False, null=False) class Meta(object): ordering = ('my_order',)
Here the ordering field is named my_order, but you may choose any other name. There are only two constraints:
my_order is the first field in the ordering tuple of the model’s Meta class.
so this will not interfere with the order of your items, even if you’re already using 0-indexed ordering fields.
The field used to store the ordering position may be any kind of numeric model field offered by Django. Use one of these models fields:
- models.PositiveIntegerField (recommended)
- models.PositiveSmallIntegerField (recommended for small sets)
Additionally you may use models.DecimalField or models.FloatField, but these model fields are not recommended.
Do not make this field unique! See below why.
In Django’s Admin, make the list view sortable¶
Next to the action checkbox, a draggable area is added to each entry line. The user than may click on any item and vertically drag that item to a new position.
Sortable List View¶
If one or more items shall be moved to another page, this can easily been done by selecting them though the action checkbox. Then the user shall click on a predefined action from the pull down menu on the top of the list view.
Integrate into a list view¶
In admin.py, add a mixin class to augment the functionality for sorting (be sure to put the mixin class before model.ModelAdmin):
from django.contrib import admin from adminsortable2.admin import SortableAdminMixin from models import MyModel class MyModelAdmin(SortableAdminMixin, admin.ModelAdmin): pass admin.site.register(MyModel, MyModelAdmin)
That’s it! The list view of the model admin interface now adds a column with a sensitive area. By clicking on that area, the user can move that row up or down. If he wants to move it to another page, he can do that as a bulk operation, using the admin actions.
Make a stacked or tabular inline view sortable¶
The interface for a sortable stacked inline view looks exactly the same. If you click on an stacked inline’s field title, this whole inline form can be moved up and down.
The interface for a sortable tabular inline view adds a sensitive area to each draggable row. These rows then can be moved up and down.
Sortable Tabular Inlines¶
After moving a tabular or stacked inline, save the model form to persist its sorting order.
Integrate into a detail view¶
from django.contrib import admin from adminsortable2.admin import SortableInlineAdminMixin from models import MySubModel, MyModel class MySubModelInline(SortableInlineAdminMixin, admin.TabularInline): # or admin.StackedInline model = MySubModel class MyModelAdmin(admin.ModelAdmin): inlines = (MySubModelInline,) admin.site.register(MyModel, MyModelAdmin)
In case you just changed your model to contain an additional sorting field (e.g. my_order), which does not yet contain any values, then you must set initial ordering values.
django-admin-sortable2 is shipping with a management command which can be used to prepopulate the ordering field:
shell> ./manage.py reorder my_app.models.MyModel
If you prefer to do a one-time database migration, just after having added the ordering field to the model, then create a datamigration:
shell> ./manage.py datamigration myapp preset_order
this creates an empty migration named something like migrations/0123_preset_order.py. Edit the file and change it into a data migration:
class Migration(DataMigration): def forwards(self, orm): order = 0 for obj in orm.MyModel.objects.all(): order += 1 obj.my_order = order obj.save()
then apply the changes to the database using:
shell> ./manage.py migrate myapp
If you omit to prepopulate the ordering field with unique values, after adding this field to an existing model, then attempting to reorder field manually will fail.
Note on unique indices on the position field¶
From a design consideration, one might be tempted to add a unique index on the ordering field. But in practice this has serious drawbacks:
MySQL has a feature (or bug?) which requires to use the ORDER BY clause in bulk updates on unique fields.
SQLite has the same bug which is even worse, because it does neither update all the fields in one transaction, nor does it allow to use the ORDER BY clause in bulk updates.
Only PostgreSQL does it “right” in the sense, that it updates all fields in one transaction and afterwards rebuilds the unique index. Here one can not use the ORDER BY clause during updates, which from the point of view for SQL semantics, is senseless anyway.
See https://code.djangoproject.com/ticket/20708 for details.
Therefore I strongly advise against setting unique=True on the position field, unless you want unportable code, which only works with Postgres databases.