Changed the way we create class names for deferred field models to avoid

problems when people have hundreds of fields on model. Maximum class
name length is now 80 characters and uses a hash when necessary.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13819 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/backends/util.py

@@ -105,15 +105,15 @@ def rev_typecast_decimal(d):
         return None
     return str(d)
 
-def truncate_name(name, length=None):
+def truncate_name(name, length=None, hash_len=4):
     """Shortens a string to a repeatable mangled version with the given length.
     """
     if length is None or len(name) <= length:
         return name
 
-    hash = md5_constructor(name).hexdigest()[:4]
+    hash = md5_constructor(name).hexdigest()[:hash_len]
 
-    return '%s%s' % (name[:length-4], hash)
+    return '%s%s' % (name[:length-hash_len], hash)
 
 def format_number(value, max_digits, decimal_places):
     """

django/db/models/query_utils.py

@@ -9,6 +9,7 @@ circular import difficulties.
 import weakref
 from django.utils.copycompat import deepcopy
 
+from django.db.backends import util
 from django.utils import tree
 from django.utils.datastructures import SortedDict
 
@@ -262,9 +263,10 @@ def deferred_class_factory(model, attrs):
 
     # The app_cache wants a unique name for each model, otherwise the new class
     # won't be created (we get an old one back). Therefore, we generate the
-    # name using the passed in attrs. It's OK to reuse an old case if the attrs
+    # name using the passed in attrs. It's OK to reuse an existing class
-    # are identical.
+    # object if the attrs are identical.
     name = "%s_Deferred_%s" % (model.__name__, '_'.join(sorted(list(attrs))))
+    name = util.truncate_name(name, 80, 32)
 
     overrides = dict([(attr, DeferredAttribute(attr, model))
             for attr in attrs])