From b58a260c56c5d05d71ac1073bc05eda8eca0ea5f Mon Sep 17 00:00:00 2001 From: Malcolm Tredinnick Date: Tue, 16 Dec 2008 06:43:18 +0000 Subject: [PATCH] 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 --- django/db/backends/mysql/validation.py | 27 ++++++++++++++++++++------ docs/ref/databases.txt | 20 +++++++++++++++++-- docs/ref/models/fields.txt | 17 ++++++++++++---- 3 files changed, 52 insertions(+), 12 deletions(-) diff --git a/django/db/backends/mysql/validation.py b/django/db/backends/mysql/validation.py index 85354a8468..3014d7bae5 100644 --- a/django/db/backends/mysql/validation.py +++ b/django/db/backends/mysql/validation.py @@ -2,12 +2,27 @@ from django.db.backends import BaseDatabaseValidation 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]]))) - \ No newline at end of file + 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]])}) + 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 diff --git a/docs/ref/models/fields.txt b/docs/ref/models/fields.txt index 4f2a92a66b..52508c7e5c 100644 --- a/docs/ref/models/fields.txt +++ b/docs/ref/models/fields.txt @@ -327,6 +327,13 @@ The admin represents this as an ```` (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 ` 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 ```` (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``.