from django.db.backends import BaseDatabaseValidation
class DatabaseValidation(BaseDatabaseValidation):
def validate_field(self, errors, opts, f):
"""
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
db_version = self.connection.get_server_version()
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).'
elif 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]])})
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