Use CachedTicket.get_or_create to avoid duplicates

src/pretix/base/migrations/0041_auto_20161018_1654.py

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.2 on 2016-10-18 16:54
+from __future__ import unicode_literals
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0040_u2fdevice'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='cachedticket',
+            name='cachedfile',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to='pretixbase.CachedFile'),
+        ),
+    ]

src/pretix/base/models/orders.py

@@ -304,7 +304,7 @@ class Order(LoggedModel):
 
 class CachedTicket(models.Model):
     order = models.ForeignKey(Order, on_delete=models.CASCADE)
-    cachedfile = models.ForeignKey(CachedFile, on_delete=models.CASCADE)
+    cachedfile = models.ForeignKey(CachedFile, on_delete=models.CASCADE, null=True)
     provider = models.CharField(max_length=255)
 
 

src/pretix/control/views/orders.py

@@ -420,19 +420,14 @@ class OrderDownload(OrderView):
             messages.error(request, _('Order is not paid.'))
             return redirect(self.get_order_url())
 
-        try:
+        ct = CachedTicket.objects.get_or_create(order=self.order, provider=self.output.identifier)[0]
-            ct = CachedTicket.objects.get(order=self.order, provider=self.output.identifier)
+        if not ct.cachedfile:
-        except CachedTicket.DoesNotExist:
-            ct = CachedTicket(order=self.order, provider=self.output.identifier)
-        try:
-            ct.cachedfile
-        except CachedFile.DoesNotExist:
             cf = CachedFile()
             cf.date = now()
             cf.expires = self.request.event.date_from + timedelta(days=30)
             cf.save()
             ct.cachedfile = cf
-        ct.save()
+            ct.save()
         if not ct.cachedfile.file.name:
             tickets.generate.apply_async(args=(self.order.id, self.output.identifier))
         return redirect(reverse('cachedfile.download', kwargs={'id': ct.cachedfile.id}))

src/pretix/presale/views/order.py

@@ -501,19 +501,14 @@ class OrderDownload(EventViewMixin, OrderDetailMixin, View):
             messages.error(request, _('Ticket download is not (yet) enabled.'))
             return redirect(self.get_order_url())
 
-        try:
+        ct = CachedTicket.objects.get_or_create(order=self.order, provider=self.output.identifier)[0]
-            ct = CachedTicket.objects.get(order=self.order, provider=self.output.identifier)
+        if not ct.cachedfile:
-        except CachedTicket.DoesNotExist:
-            ct = CachedTicket(order=self.order, provider=self.output.identifier)
-        try:
-            ct.cachedfile
-        except CachedFile.DoesNotExist:
             cf = CachedFile()
             cf.date = now()
             cf.expires = self.request.event.date_from + timedelta(days=30)
             cf.save()
             ct.cachedfile = cf
-        ct.save()
+            ct.save()
         generate.apply_async(args=(self.order.id, self.output.identifier))
         return redirect(reverse('cachedfile.download', kwargs={'id': ct.cachedfile.id}))