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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
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@ -2,12 +2,27 @@ from django.db.backends import BaseDatabaseValidation
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class DatabaseValidation(BaseDatabaseValidation):
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def validate_field(self, errors, opts, f):
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"Prior to MySQL 5.0.3, character fields could not exceed 255 characters"
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"""
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There are some field length restrictions for MySQL:
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- Prior to version 5.0.3, character fields could not exceed 255
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characters in length.
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- No character (varchar) fields can have a length exceeding 255
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characters if they have a unique index on them.
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"""
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from django.db import models
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from django.db import connection
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db_version = connection.get_server_version()
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if db_version < (5, 0, 3) and isinstance(f, (models.CharField, models.CommaSeparatedIntegerField, models.SlugField)) and f.max_length > 255:
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errors.add(opts,
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'"%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).' %
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(f.name, f.__class__.__name__, '.'.join([str(n) for n in db_version[:3]])))
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varchar_fields = (models.CharField, models.CommaSeparatedIntegerField,
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models.SlugField)
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if isinstance(f, varchar_fields) and f.max_length > 255:
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if db_version < (5, 0, 3):
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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).'
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if f.unique == True:
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msg = '"%(name)s": %(cls)s cannot have a "max_length" greater than 255 when using "unique=True".'
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else:
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msg = None
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if msg:
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errors.add(opts, msg % {'name': f.name, 'cls': f.__class__.__name__, 'version': '.'.join([str(n) for n in db_version[:3]])})
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@ -234,8 +234,11 @@ storage engine, you have a couple of options.
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.. _AlterModelOnSyncDB: http://code.djangoproject.com/wiki/AlterModelOnSyncDB
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Boolean fields in Django
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-------------------------
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Notes on specific fields
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------------------------
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Boolean fields
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~~~~~~~~~~~~~~
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Since MySQL doesn't have a direct ``BOOLEAN`` column type, Django uses a
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``TINYINT`` column with values of ``1`` and ``0`` to store values for the
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@ -244,6 +247,19 @@ of that field for more details, but usually this won't be something that will
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matter unless you're printing out the field values and are expecting to see
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``True`` and ``False.``.
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Character fields
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~~~~~~~~~~~~~~~~
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Any fields that are stored with ``VARCHAR`` column types have their
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``max_length`` restricted to 255 characters if you are using ``unique=True``
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for the field. This affects :class:`~django.db.models.CharField`,
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:class:`~django.db.models.SlugField` and
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:class:`~django.db.models.CommaSeparatedIntegerField`.
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Furthermore, if you are using a version of MySQL prior to 5.0.3, all of those
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column types have a maximum length restriction of 255 characters, regardless
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of whether ``unique=True`` is specified or not.
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.. _sqlite-notes:
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SQLite notes
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@ -327,6 +327,13 @@ The admin represents this as an ``<input type="text">`` (a single-line input).
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The maximum length (in characters) of the field. The max_length is enforced
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at the database level and in Django's validation.
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.. note::
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If you are writing an application that must be portable to multiple
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database backends, you should be aware that there are restrictions on
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``max_length`` for some backends. Refer to the :ref:`database backend
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notes <ref-databases>` for details.
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.. admonition:: MySQL users
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If you are using this field with MySQLdb 1.2.2 and the ``utf8_bin``
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@ -341,7 +348,8 @@ The admin represents this as an ``<input type="text">`` (a single-line input).
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.. class:: CommaSeparatedIntegerField(max_length=None, [**options])
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A field of integers separated by commas. As in :class:`CharField`, the
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:attr:`~CharField.max_length` argument is required.
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:attr:`~CharField.max_length` argument is required and the note about database
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portability mentioned there should be heeded.
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``DateField``
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-------------
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@ -654,9 +662,10 @@ Like a :class:`PositiveIntegerField`, but only allows values under a certain
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containing only letters, numbers, underscores or hyphens. They're generally used
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in URLs.
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Like a CharField, you can specify :attr:`~CharField.max_length`. If
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:attr:`~CharField.max_length` is not specified, Django will use a default length
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of 50.
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Like a CharField, you can specify :attr:`~CharField.max_length` (read the note
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about database portability and :attr:`~CharField.max_length` in that section,
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too). If :attr:`~CharField.max_length` is not specified, Django will use a
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default length of 50.
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Implies setting :attr:`Field.db_index` to ``True``.
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