diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/ref/databases.txt | 20 | ||||
| -rw-r--r-- | docs/ref/models/fields.txt | 17 |
2 files changed, 31 insertions, 6 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 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 ``<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``. |