Fixed #21351 -- Replaced memoize with Python's lru_cache.

Replaced the custom, untested memoize with a similar decorator from Python's
3.2 stdlib. Although some minor performance degradation (see ticket), it is
expected that in the long run lru_cache will outperform memoize once it is
implemented in C.

Thanks to EvilDMP for the report and Baptiste Mispelon for the idea of
replacing memoize with lru_cache.

2 files changed, 12 insertions, 0 deletions

diff --git a/docs/internals/deprecation.txt b/docs/internals/deprecation.txt
index f2e2c4c2f7..f2d121e641 100644
--- a/docs/internals/deprecation.txt
+++ b/docs/internals/deprecation.txt
@@ -479,6 +479,8 @@ these changes.
 * The ``zh-cn`` and ``zh-tw`` language codes will be removed and have been
   replaced by the ``zh-hans`` and ``zh-hant`` language code respectively.
 
+* The internal ``django.utils.functional.memoize`` will be removed.
+
 2.0
 ---
 
diff --git a/docs/releases/1.7.txt b/docs/releases/1.7.txt
index 2aab6f26a7..d703f44e4b 100644
--- a/docs/releases/1.7.txt
+++ b/docs/releases/1.7.txt
@@ -752,3 +752,13 @@ recently introduced language codes ``zh-hans`` and ``zh-hant`` respectively.
 If you use these language codes, you should rename the locale directories
 and update your settings to reflect these changes. The deprecated language
 codes will be removed in Django 1.9.
+
+``django.utils.functional.memoize`` function
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The function ``memoize`` is deprecated and should be replaced by the
+``functools.lru_cache`` decorator (available from Python 3.2 onwards).
+
+Django ships a backport of this decorator for older Python versions and it's
+available at ``django.utils.lru_cache.lru_cache``. The deprecated function will
+be removed in Django 1.9.