Creates new semi-functional migration

bookwyrm/migrations/0046_reviewrating.py

@@ -0,0 +1,59 @@
+# Generated by Django 3.0.7 on 2021-02-25 18:36
+
+from django.db import migrations, models
+from django.db import connection
+from django.db.models import Q
+import django.db.models.deletion
+
+def convert_review_rating(app_registry, schema_editor):
+    ''' take rating type Reviews and conver them to ReviewRatings '''
+    db_alias = schema_editor.connection.alias
+
+    reviews = app_registry.get_model(
+        'bookwyrm', 'Review'
+    ).objects.using(db_alias).filter(
+        Q(content__isnull=True) | Q(content='')
+    )
+
+    with connection.cursor() as cursor:
+        for review in reviews:
+            cursor.execute('''
+INSERT INTO bookwyrm_reviewrating(review_ptr_id)
+SELECT status_ptr_id FROM bookwyrm_review
+WHERE status_ptr_id={:d}'''.format(review.id))
+
+def unconvert_review_rating(app_registry, schema_editor):
+    ''' undo the conversion from ratings back to reviews'''
+    # TODO: this does not work
+    db_alias = schema_editor.connection.alias
+
+    ratings = app_registry.get_model(
+        'bookwyrm', 'ReviewRating'
+    ).objects.using(db_alias).all()
+
+    with connection.cursor() as cursor:
+        for rating in ratings:
+            cursor.execute('''
+INSERT INTO bookwyrm_review(status_ptr_id)
+SELECT review_ptr_id FROM bookwyrm_reviewrating
+WHERE review_ptr_id={:d}'''.format(rating.id))
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('bookwyrm', '0045_auto_20210210_2114'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='ReviewRating',
+            fields=[
+                ('review_ptr', models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='bookwyrm.Review')),
+            ],
+            options={
+                'abstract': False,
+            },
+            bases=('bookwyrm.review',),
+        ),
+        migrations.RunPython(convert_review_rating, unconvert_review_rating),
+    ]