Add support for prefetching fields
This makes it possible to specify the fields that should be
prefetched as part of a getForFields query. Doing a prefetch on a
ReferenceProperty when it is known that the property will be
referenced in (almost all) entities is far more efficient than
doing the invididual fetches sequentially.
from django.db.backends import BaseDatabaseValidation
class DatabaseValidation(BaseDatabaseValidation):
def validate_field(self, errors, opts, f):
"Prior to MySQL 5.0.3, character fields could not exceed 255 characters"
from django.db import models
from django.db import connection
db_version = connection.get_server_version()
if db_version < (5, 0, 3) and isinstance(f, (models.CharField, models.CommaSeparatedIntegerField, models.SlugField)) and f.max_length > 255:
errors.add(opts,
'"%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).' %
(f.name, f.__class__.__name__, '.'.join([str(n) for n in db_version[:3]])))