1 from django.db.backends import BaseDatabaseValidation

     2 

     3 class DatabaseValidation(BaseDatabaseValidation):

     4     def validate_field(self, errors, opts, f):

     5         """

     6         There are some field length restrictions for MySQL:

     7 

     8         - Prior to version 5.0.3, character fields could not exceed 255

     9           characters in length.

    10         - No character (varchar) fields can have a length exceeding 255

    11           characters if they have a unique index on them.

    12         """

    13         from django.db import models

    14         from django.db import connection

    15         db_version = connection.get_server_version()

    16         varchar_fields = (models.CharField, models.CommaSeparatedIntegerField,

    17                 models.SlugField)

    18         if isinstance(f, varchar_fields) and f.max_length > 255:

    19             if db_version < (5, 0, 3):

    20                 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).'

    21             elif f.unique == True:

    22                 msg = '"%(name)s": %(cls)s cannot have a "max_length" greater than 255 when using "unique=True".'

    23             else:

    24                 msg = None

    25 

    26             if msg:

    27                 errors.add(opts, msg % {'name': f.name, 'cls': f.__class__.__name__, 'version': '.'.join([str(n) for n in db_version[:3]])})

    28