Fixed #20584 -- Fixed memcached's get_many() with single-use iterators.

Thanks Guyon Morée for the report.

AUTHORS

@@ -168,6 +168,7 @@ answer newbie questions, and generally made Django that much better:
     Chris Jones <chris@brack3t.com>
     Chris Lamb <chris@chris-lamb.co.uk>
     Chris Streeter <chris@chrisstreeter.com>
+    Christian Barcenas <christian@cbarcenas.com>
     Christian Metts
     Christian Oudard <christian.oudard@gmail.com>
     Christian Tanzer <tanzer@swing.co.at>

django/core/cache/backends/memcached.py

@@ -84,12 +84,9 @@ class BaseMemcachedCache(BaseCache):
         self._cache.delete(key)
 
     def get_many(self, keys, version=None):
-        new_keys = [self.make_key(x, version=version) for x in keys]
-        ret = self._cache.get_multi(new_keys)
-        if ret:
-            m = dict(zip(new_keys, keys))
-            return {m[k]: v for k, v in ret.items()}
-        return ret
+        key_map = {self.make_key(key, version=version): key for key in keys}
+        ret = self._cache.get_multi(key_map.keys())
+        return {key_map[k]: v for k, v in ret.items()}
 
     def close(self, **kwargs):
         # Many clients don't clean up connections properly.

tests/cache/tests.py

@@ -312,6 +312,7 @@ class BaseCacheTests:
         cache.set('d', 'd')
         self.assertEqual(cache.get_many(['a', 'c', 'd']), {'a': 'a', 'c': 'c', 'd': 'd'})
         self.assertEqual(cache.get_many(['a', 'b', 'e']), {'a': 'a', 'b': 'b'})
+        self.assertEqual(cache.get_many(iter(['a', 'b', 'e'])), {'a': 'a', 'b': 'b'})
 
     def test_delete(self):
         # Cache keys can be deleted