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[1.0.X] Fixed #9431 -- Added extra validation for VARCHAR-based field…

…s on MySQL.

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

Backport of r9470 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@9652 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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commit 01e04e90e0f69e3b350301015f17a6cb4aa7d39a 1 parent 518c4ca
Malcolm Tredinnick malcolmt authored
27 django/db/backends/mysql/validation.py
View
@@ -2,12 +2,27 @@
class DatabaseValidation(BaseDatabaseValidation):
def validate_field(self, errors, opts, f):
- "Prior to MySQL 5.0.3, character fields could not exceed 255 characters"
+ """
+ There are some field length restrictions for MySQL:
+
+ - Prior to version 5.0.3, character fields could not exceed 255
+ characters in length.
+ - No character (varchar) fields can have a length exceeding 255
+ characters if they have a unique index on them.
+ """
from django.db import models
from django.db import connection
db_version = connection.get_server_version()
- if db_version < (5, 0, 3) and isinstance(f, (models.CharField, models.CommaSeparatedIntegerField, models.SlugField)) and f.max_length > 255:
- errors.add(opts,
- '"%s": %s cannot have a "max_length" greater than 255 when you are using a version of MySQL prior to 5.0.3 (you are using %s).' %
- (f.name, f.__class__.__name__, '.'.join([str(n) for n in db_version[:3]])))
-
+ varchar_fields = (models.CharField, models.CommaSeparatedIntegerField,
+ models.SlugField)
+ if isinstance(f, varchar_fields) and f.max_length > 255:
+ if db_version < (5, 0, 3):
+ msg = '"%(name)s": %(cls)s cannot have a "max_length" greater than 255 when you are using a version of MySQL prior to 5.0.3 (you are using %(version)s).'
+ if f.unique == True:
+ msg = '"%(name)s": %(cls)s cannot have a "max_length" greater than 255 when using "unique=True".'
+ else:
+ msg = None
+
+ if msg:
+ errors.add(opts, msg % {'name': f.name, 'cls': f.__class__.__name__, 'version': '.'.join([str(n) for n in db_version[:3]])})
+
20 docs/ref/databases.txt
View
@@ -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
17 docs/ref/models/fields.txt
View
@@ -327,6 +327,13 @@ The admin represents this as an ``<input type="text">`` (a single-line input).
The maximum length (in characters) of the field. The max_length is enforced
at the database level and in Django's validation.
+.. note::
+
+ If you are writing an application that must be portable to multiple
+ database backends, you should be aware that there are restrictions on
+ ``max_length`` for some backends. Refer to the :ref:`database backend
+ notes <ref-databases>` for details.
+
.. admonition:: MySQL users
If you are using this field with MySQLdb 1.2.2 and the ``utf8_bin``
@@ -341,7 +348,8 @@ The admin represents this as an ``<input type="text">`` (a single-line input).
.. class:: CommaSeparatedIntegerField(max_length=None, [**options])
A field of integers separated by commas. As in :class:`CharField`, the
-:attr:`~CharField.max_length` argument is required.
+:attr:`~CharField.max_length` argument is required and the note about database
+portability mentioned there should be heeded.
``DateField``
-------------
@@ -654,9 +662,10 @@ Like a :class:`PositiveIntegerField`, but only allows values under a certain
containing only letters, numbers, underscores or hyphens. They're generally used
in URLs.
-Like a CharField, you can specify :attr:`~CharField.max_length`. If
-:attr:`~CharField.max_length` is not specified, Django will use a default length
-of 50.
+Like a CharField, you can specify :attr:`~CharField.max_length` (read the note
+about database portability and :attr:`~CharField.max_length` in that section,
+too). If :attr:`~CharField.max_length` is not specified, Django will use a
+default length of 50.
Implies setting :attr:`Field.db_index` to ``True``.
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