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 from django.db import connection db_version = 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]])})