models: Split Patch into two models

There are a lot of similarities between cover letters and patches: so
many, in fact, that it would be helpful to occasionally treat them as
the same thing. Achieve this by extracting out the fields that would be
shared between a Patch and a hypothetical cover letter into a "sub
model". This allows us to do cool stuff like assigning comments to both
patches and cover letters or listing both patches and cover letters on
the main screen in a natural way.

The migrations for this are really the only complicated part. There are
three, broken up into schema and data migrations per Django customs,
and they works as follows:

* Rename the 'Patch' model to 'Submission', then create a subclass
  called 'Patch' that includes duplicates of the patch-specific fields
  of Submission (with changed names to prevent conflicts). Rename
  non-patch specific references to the renamed 'Submission' model
  as necessary.
* Duplicate the contents of the patch-specific fields from 'Submission'
  to 'Patch'
* Remove the patch-specific fields from 'Submission', renaming the
  'Patch' model to take their place. Update the patch-specific
  references to point the new 'Patch' model, rather than 'Submission'.

This comes at the cost of an additional JOIN per item on the main
screen, but this seems a small price to pay for the additional
functionality gained. To minimise this, however, caching will be added.

Signed-off-by: Stephen Finucane <stephen.finucane@intel.com>
Signed-off-by: Andy Doan <andy.doan@linaro.org>

3 files changed, 231 insertions, 0 deletions

diff --git a/patchwork/migrations/0009_add_submission_model.py b/patchwork/migrations/0009_add_submission_model.py
new file mode 100644
index 0000000..6bb68fb
--- /dev/null
+++ b/patchwork/migrations/0009_add_submission_model.py
@@ -0,0 +1,80 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.db import migrations, models
+
+import patchwork.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('patchwork', '0008_add_email_mixin'),
+    ]
+
+    operations = [
+        # Rename the 'Patch' to 'Submission'
+        migrations.RenameModel(
+            old_name='Patch',
+            new_name='Submission'
+        ),
+        migrations.AlterModelOptions(
+            name='submission',
+            options={'ordering': ['date']},
+        ),
+
+        # Rename the non-Patch specific references to point to Submission
+        migrations.RenameField(
+            model_name='comment',
+            old_name='patch',
+            new_name='submission',
+        ),
+        migrations.AlterUniqueTogether(
+            name='comment',
+            unique_together=set([('msgid', 'submission')]),
+        ),
+        migrations.RenameField(
+            model_name='userprofile',
+            old_name='patches_per_page',
+            new_name='items_per_page',
+        ),
+        migrations.AlterField(
+            model_name='userprofile',
+            name='items_per_page',
+            field=models.PositiveIntegerField(
+                default=100,
+                help_text=b'Number of items to display per page'),
+        ),
+
+        # Recreate the 'Patch' model as a subclass of 'Submission'. Each field
+        # is given a unique name to prevent it conflicting with the same field
+        # found in the 'Submission' "super model". We will fix this later.
+        migrations.CreateModel(
+            name='Patch',
+            fields=[
+                ('submission_ptr', models.OneToOneField(
+                    parent_link=True, auto_created=True, primary_key=True,
+                    serialize=False, to='patchwork.Submission')),
+                ('diff2', models.TextField(null=True, blank=True)),
+                ('commit_ref2', models.CharField(
+                    max_length=255, null=True, blank=True)),
+                ('pull_url2', models.CharField(
+                    max_length=255, null=True, blank=True)),
+                # we won't migrate the data of this, seeing as it's
+                # automatically recreated every time we save a Patch
+                ('tags2', models.ManyToManyField(
+                    to='patchwork.Tag', through='patchwork.PatchTag')),
+                ('delegate2', models.ForeignKey(
+                    blank=True, to=settings.AUTH_USER_MODEL, null=True)),
+                ('state2', models.ForeignKey(to='patchwork.State')),
+                ('archived2', models.BooleanField(default=False)),
+                ('hash2', patchwork.models.HashField(
+                    max_length=40, null=True, blank=True)),
+            ],
+            options={
+                'verbose_name_plural': 'Patches',
+            },
+            bases=('patchwork.submission',),
+        ),
+    ]
diff --git a/patchwork/migrations/0010_migrate_data_from_submission_to_patch.py b/patchwork/migrations/0010_migrate_data_from_submission_to_patch.py
new file mode 100644
index 0000000..1d4b6e1
--- /dev/null
+++ b/patchwork/migrations/0010_migrate_data_from_submission_to_patch.py
@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('patchwork', '0009_add_submission_model'),
+    ]
+
+    operations = [
+        migrations.RunSQL(
+            ['''INSERT INTO patchwork_patch
+                  (submission_ptr_id, diff2, commit_ref2, pull_url2,
+                   delegate2_id, state2_id, archived2, hash2)
+                SELECT id, diff, commit_ref, pull_url, delegate_id, state_id,
+                       archived, hash
+                FROM patchwork_submission
+                '''],
+            ['''UPDATE patchwork_submission SET
+                  diff=diff2, commit_ref=commit_ref2, pull_url=pull_url2,
+                  delegate_id=delegate2_id, state_id=state2_id,
+                  archived=archived2, hash=hash2
+                FROM patchwork_patch WHERE
+                  patchwork_submission.id = patchwork_patch.submission_ptr_id
+                ''']
+        ),
+    ]
diff --git a/patchwork/migrations/0011_remove_temp_fields.py b/patchwork/migrations/0011_remove_temp_fields.py
new file mode 100644
index 0000000..6b159c5
--- /dev/null
+++ b/patchwork/migrations/0011_remove_temp_fields.py
@@ -0,0 +1,121 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('patchwork', '0010_migrate_data_from_submission_to_patch'),
+    ]
+
+    operations = [
+        # Remove duplicate fields from 'Submission' and rename 'Patch' version
+        migrations.RemoveField(
+            model_name='submission',
+            name='diff',
+        ),
+        migrations.RenameField(
+            model_name='patch',
+            old_name='diff2',
+            new_name='diff',
+        ),
+        migrations.RemoveField(
+            model_name='submission',
+            name='commit_ref',
+        ),
+        migrations.RenameField(
+            model_name='patch',
+            old_name='commit_ref2',
+            new_name='commit_ref',
+        ),
+        migrations.RemoveField(
+            model_name='submission',
+            name='pull_url',
+        ),
+        migrations.RenameField(
+            model_name='patch',
+            old_name='pull_url2',
+            new_name='pull_url',
+        ),
+        migrations.RemoveField(
+            model_name='submission',
+            name='tags',
+        ),
+        migrations.RenameField(
+            model_name='patch',
+            old_name='tags2',
+            new_name='tags',
+        ),
+        migrations.RemoveField(
+            model_name='submission',
+            name='delegate',
+        ),
+        migrations.RenameField(
+            model_name='patch',
+            old_name='delegate2',
+            new_name='delegate',
+        ),
+        migrations.RemoveField(
+            model_name='submission',
+            name='state',
+        ),
+        migrations.RenameField(
+            model_name='patch',
+            old_name='state2',
+            new_name='state',
+        ),
+        migrations.RemoveField(
+            model_name='submission',
+            name='archived',
+        ),
+        migrations.RenameField(
+            model_name='patch',
+            old_name='archived2',
+            new_name='archived',
+        ),
+        migrations.RemoveField(
+            model_name='submission',
+            name='hash',
+        ),
+        migrations.RenameField(
+            model_name='patch',
+            old_name='hash2',
+            new_name='hash',
+        ),
+        # Update any many-to-many fields to point to Patch now
+        migrations.AlterField(
+            model_name='bundle',
+            name='patches',
+            field=models.ManyToManyField(to='patchwork.Patch',
+                                         through='patchwork.BundlePatch'),
+        ),
+        migrations.AlterField(
+            model_name='bundlepatch',
+            name='patch',
+            field=models.ForeignKey(to='patchwork.Patch'),
+        ),
+        migrations.AlterField(
+            model_name='check',
+            name='patch',
+            field=models.ForeignKey(to='patchwork.Patch'),
+        ),
+        migrations.AlterField(
+            model_name='patch',
+            name='state',
+            field=models.ForeignKey(to='patchwork.State', null=True),
+        ),
+        migrations.AlterField(
+            model_name='patchchangenotification',
+            name='patch',
+            field=models.OneToOneField(primary_key=True,
+                                       serialize=False,
+                                       to='patchwork.Patch'),
+        ),
+        migrations.AlterField(
+            model_name='patchtag',
+            name='patch',
+            field=models.ForeignKey(to='patchwork.Patch'),
+        ),
+    ]