Fixed #9431 -- Added extra validation for VARCHAR-based fields on MySQL.

max_length > 255 and unique=True is not permitted. Based on a patch from
adamnelson.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@9650 bcc190cf-cafb-0310-a4f2-bffc1f526a37

1 files changed, 18 insertions, 2 deletions

diff --git a/docs/ref/databases.txt b/docs/ref/databases.txt
index 79e6136104..0b5a819898 100644
--- a/docs/ref/databases.txt
+++ b/docs/ref/databases.txt
@@ -234,8 +234,11 @@ storage engine, you have a couple of options.
 
 .. _AlterModelOnSyncDB: http://code.djangoproject.com/wiki/AlterModelOnSyncDB
 
-Boolean fields in Django
--------------------------
+Notes on specific fields
+------------------------
+
+Boolean fields
+~~~~~~~~~~~~~~
 
 Since MySQL doesn't have a direct ``BOOLEAN`` column type, Django uses a
 ``TINYINT`` column with values of ``1`` and ``0`` to store values for the
@@ -244,6 +247,19 @@ of that field for more details, but usually this won't be something that will
 matter unless you're printing out the field values and are expecting to see
 ``True`` and ``False.``.
 
+Character fields
+~~~~~~~~~~~~~~~~
+
+Any fields that are stored with ``VARCHAR`` column types have their
+``max_length`` restricted to 255 characters if you are using ``unique=True``
+for the field. This affects :class:`~django.db.models.CharField`,
+:class:`~django.db.models.SlugField` and
+:class:`~django.db.models.CommaSeparatedIntegerField`.
+
+Furthermore, if you are using a version of MySQL prior to 5.0.3, all of those
+column types have a maximum length restriction of 255 characters, regardless
+of whether ``unique=True`` is specified or not.
+
 .. _sqlite-notes:
 
 SQLite notes