Refactor: remove Filter as a Django model.

CHANGELOG.txt

@@ -11,6 +11,7 @@ Changelog
  * `FieldRowPanel` now creates equal-width columns automatically if `col*` classnames are not specified (Chris Rogers)
  * Form builder now validates against multiple fields with the same name (Richard McMillan)
  * The 'choices' field on the form builder no longer has a maximum length (Johannes Spielmann)
+ * The wagtailimages.Filter model has been removed, and converted to a Python class instead (Gagaro)
  * Fix: Email templates and document uploader now support custom `STATICFILES_STORAGE` (Jonny Scholes)
  * Fix: Removed alignment options (deprecated in HTML and not rendered by Wagtail) from `TableBlock` context menu (Moritz Pfeiffer)
  * Fix: Fixed incorrect CSS path on ModelAdmin's "choose a parent page" view
@@ -21,7 +22,6 @@ Changelog
 
  * Fixed regression in 1.5.1 on editing external links (Stephen Rice)
 
-
 1.5.1 (07.06.2016)
 ~~~~~~~~~~~~~~~~~~
 

docs/releases/1.6.rst

@@ -21,6 +21,7 @@ Minor features
  * ``FieldRowPanel`` now creates equal-width columns automatically if ``col*`` classnames are not specified (Chris Rogers)
  * Form builder now validates against multiple fields with the same name (Richard McMillan)
  * The 'choices' field on the form builder no longer has a maximum length (Johannes Spielmann)
+ * The wagtailimages.Filter model has been removed, and converted to a Python class instead (Gagaro)
 
 
 Bug fixes
@@ -39,3 +40,8 @@ Form builder ``FormField`` models require a migration
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 The ``choices`` field on the ``wagtailforms.models.AbstractFormField`` model has been changed from a ``CharField`` to a ``TextField``, to allow it to be of unlimited length. If you are using the ``wagtailforms`` module in your project, you will need to run ``python manage.py makemigrations`` and ``python manage.py migrate`` after upgrading, in order to apply this change to your form page models.
+
+``wagtailimages.Filter`` model has been removed
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The ``wagtailimages.Filter`` model has been removed, and replaced with a ``Filter`` class instead. This class can be imported from the same location as the model: ``wagtail.wagtailimages.models.Filter``. The ``Filter`` class has the same API as the ``Filter`` model did, with the exception that Model methods such as ``Filter.save()``, and ``Filter.objects.get()`` have been removed.

wagtail/contrib/modeladmin/options.py

@@ -74,8 +74,7 @@ class ThumbnailMixin(object):
             'class': self.thumb_classname,
         }
         if image:
-            fltr, _ = Filter.objects.get_or_create(
-                spec=self.thumb_image_filter_spec)
+            fltr = Filter(spec=self.thumb_image_filter_spec)
             img_attrs.update({'src': image.get_rendition(fltr).url})
             return mark_safe('<img{}>'.format(flatatt(img_attrs)))
         elif self.thumb_default:

wagtail/contrib/modeladmin/views.py

@@ -872,7 +872,7 @@ class InspectView(InstanceSpecificView):
         """ Render an image """
         image = getattr(self.instance, field_name)
         if image:
-            fltr, _ = Filter.objects.get_or_create(spec='max-400x400')
+            fltr = Filter(spec='max-400x400')
             rendition = image.get_rendition(fltr)
             return rendition.img_tag
         return self.model_admin.get_empty_value_display(field_name)

wagtail/wagtailimages/migrations/0014_remove_filter_model.py

@@ -0,0 +1,56 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+def forwards_data_migration(apps, schema_editor):
+    Rendition = apps.get_model('wagtailimages', 'Rendition')
+    db_alias = schema_editor.connection.alias
+    # update doesn't work during migration, we have to do it one by one
+    for rendition in Rendition.objects.using(db_alias).select_related('filter').all():
+        rendition.filter2 = rendition.filter.spec
+        rendition.save()
+
+
+def reverse_data_migration(apps, schema_editor):
+    Rendition = apps.get_model('wagtailimages', 'Rendition')
+    Filter = apps.get_model('wagtailimages', 'Filter')
+    db_alias = schema_editor.connection.alias
+    renditions = Rendition.objects.using(db_alias).all()
+    for rendition in renditions:
+        # Ensure we don't create the same Filter twice
+        rendition.filter, _ = Filter.objects.get_or_create(spec=rendition.filter2)
+        rendition.save()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('wagtailimages', '0013_make_rendition_upload_callable'),
+    ]
+
+    operations = [
+        # We create a new attribute to allow the data migration (filter -> filter2).
+        migrations.AddField(
+            model_name='Rendition',
+            name='filter2',
+            field=models.CharField(max_length=255, default=''),
+            preserve_default=False,
+        ),
+        # Allow NULL for backward operation to work (no temporary default value possible as the `spec` attribute is not null but also unique).
+        migrations.AlterField('rendition', 'filter', models.ForeignKey(on_delete=models.CASCADE, related_name='+', to='wagtailimages.Filter', null=True)),
+        # Remove unique constraint to allow the removal of `filter` field.
+        migrations.AlterUniqueTogether('rendition', set([])),
+        # Migrate data.
+        migrations.RunPython(forwards_data_migration, reverse_data_migration),
+        # We can now delete Filter for good.
+        migrations.RemoveField(model_name='Rendition', name='filter'),
+        migrations.DeleteModel('Filter'),
+        # And we can finally set the new attribute as `filter`.
+        migrations.RenameField(model_name='Rendition', old_name='filter2', new_name='filter'),
+        # Bug with mysql and postgresql, we need to add the index after the renaming (https://code.djangoproject.com/ticket/25530).
+        migrations.AlterField('rendition', 'filter', models.CharField(max_length=255, db_index=True)),
+        # We can now set back the unique constraint.
+        migrations.AlterUniqueTogether('rendition', set([('image', 'filter', 'focal_point_key')])),
+    ]

wagtail/wagtailimages/models.py

@@ -251,14 +251,14 @@ class AbstractImage(CollectionMember, TagSearchable):
 
     def get_rendition(self, filter):
         if isinstance(filter, string_types):
-            filter, created = Filter.objects.get_or_create(spec=filter)
+            filter = Filter(spec=filter)
 
         cache_key = filter.get_cache_key(self)
         Rendition = self.get_rendition_model()
 
         try:
             rendition = self.renditions.get(
-                filter=filter,
+                filter=filter.spec,
                 focal_point_key=cache_key,
             )
         except Rendition.DoesNotExist:
@@ -285,7 +285,7 @@ class AbstractImage(CollectionMember, TagSearchable):
             output_filename = output_filename_without_extension + '.' + output_extension
 
             rendition, created = self.renditions.get_or_create(
-                filter=filter,
+                filter=filter.spec,
                 focal_point_key=cache_key,
                 defaults={'file': File(generated_image.f, name=output_filename)}
             )
@@ -367,15 +367,16 @@ def get_image_model():
     return image_model
 
 
-class Filter(models.Model):
+class Filter(object):
     """
     Represents one or more operations that can be applied to an Image to produce a rendition
     appropriate for final display on the website. Usually this would be a resize operation,
     but could potentially involve colour processing, etc.
     """
 
-    # The spec pattern is operation1-var1-var2|operation2-var1
-    spec = models.CharField(max_length=255, unique=True)
+    def __init__(self, spec):
+        # The spec pattern is operation1-var1-var2|operation2-var1
+        self.spec = spec
 
     @cached_property
     def operations(self):
@@ -455,7 +456,7 @@ class Filter(models.Model):
 
 
 class AbstractRendition(models.Model):
-    filter = models.ForeignKey(Filter, related_name='+')
+    filter = models.CharField(max_length=255, db_index=True)
     file = models.ImageField(upload_to=get_rendition_upload_to, width_field='width', height_field='height')
     width = models.IntegerField(editable=False)
     height = models.IntegerField(editable=False)

wagtail/wagtailimages/templatetags/wagtailimages_tags.py

@@ -74,8 +74,7 @@ class ImageNode(template.Node):
 
     @cached_property
     def filter(self):
-        _filter, _ = Filter.objects.get_or_create(spec=self.filter_spec)
-        return _filter
+        return Filter(spec=self.filter_spec)
 
     def render(self, context):
         try: