A nakonec to stejně SQL je...

seminar/migrations/fix_0058.py

@@ -1,11 +1,6 @@
 from django.db import migrations
 
-def oprav_ulohy(apps, schema_editor):
-	Problem = apps.get_model('seminar', 'Pohadka')
-
-	for p in Problem.objects.filter(typ="b'uloha'"):
-		p.typ = "uloha"
-		p.save()
+sql = "update seminar_problemy set typ = 'uloha' where typ like 'b_uloha_';"
 
 class Migration(migrations.Migration):
 
@@ -14,6 +9,6 @@ class Migration(migrations.Migration):
 	]
 
 	operations = [
-		migrations.RunPython(oprav_ulohy, oprav_ulohy),
+		migrations.RunSQL(sql, sql),
 	]