From 777a663896fcb937f2cf6987794242081b6e4808 Mon Sep 17 00:00:00 2001
From: Thomas Adamcik <thomas@adamcik.no>
Date: Sat, 11 Apr 2015 01:10:00 +0200
Subject: [PATCH] models: Take advantage of fact that our hash won't change

This might just be pointless micro-optimization as I have _not_ measured. But
it seemed silly to recursively hash everything in a model each time a hash is
required. As we know the data can not change.
---
 mopidy/models.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/mopidy/models.py b/mopidy/models.py
index 230c86cc..03f991ab 100644
--- a/mopidy/models.py
+++ b/mopidy/models.py
@@ -148,7 +148,7 @@ class ImmutableObjectMeta(type):
 
         attrs['_fields'] = fields
         attrs['_instances'] = weakref.WeakValueDictionary()
-        attrs['__slots__'] = fields.values()
+        attrs['__slots__'] = ['_hash'] + fields.values()
 
         anncestors = [b for base in bases for b in inspect.getmro(base)]
         for anncestor in anncestors:
@@ -218,10 +218,12 @@ class ImmutableObject(object):
         }
 
     def __hash__(self):
-        hash_sum = 0
-        for key, value in self._items():
-            hash_sum += hash(key) + hash(value)
-        return hash_sum
+        if not hasattr(self, '_hash'):
+            hash_sum = 0
+            for key, value in self._items():
+                hash_sum += hash(key) + hash(value)
+            super(ImmutableObject, self).__setattr__('_hash', hash_sum)
+        return self._hash
 
     def __eq__(self, other):
         if not isinstance(other, self.__class__):
@@ -267,6 +269,7 @@ class ImmutableObject(object):
                 raise TypeError(
                     'copy() got an unexpected keyword argument "%s"' % key)
             super(ImmutableObject, other).__setattr__(key, value)
+        super(ImmutableObject, other).__delattr__('_hash')
         return self._instances.setdefault(weakref.ref(other), other)
 
     def serialize(self):