Change robot deletions to set the performer to null, rather than attempting to delete the rows from the large log entries table

data/database.py

@@ -122,8 +122,9 @@ def close_db_filter(_):
 
 
 class QuayUserField(ForeignKeyField):
-  def __init__(self, allows_robots=False, *args, **kwargs):
+  def __init__(self, allows_robots=False, robot_null_delete=False, *args, **kwargs):
     self.allows_robots = allows_robots
+    self.robot_null_delete = robot_null_delete
     if not 'rel_model' in kwargs:
       kwargs['rel_model'] = User
 
@@ -157,7 +158,11 @@ class User(BaseModel):
       for query, fk in self.dependencies(search_nullable=True):
         if isinstance(fk, QuayUserField) and fk.allows_robots:
           model = fk.model_class
-          model.delete().where(query).execute()
+
+          if fk.robot_null_delete:
+            model.update(**{fk.name: None}).where(query).execute()
+          else:
+            model.delete().where(query).execute()
 
       # Delete the instance itself.
       super(User, self).delete_instance(recursive=False, delete_nullable=False)
@@ -459,7 +464,7 @@ class LogEntry(BaseModel):
   kind = ForeignKeyField(LogEntryKind, index=True)
   account = QuayUserField(index=True, related_name='account')
   performer = QuayUserField(allows_robots=True, index=True, null=True,
-                            related_name='performer')
+                            related_name='performer', robot_null_delete=True)
   repository = ForeignKeyField(Repository, index=True, null=True)
   datetime = DateTimeField(default=datetime.now, index=True)
   ip = CharField(null=True)