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There are several Django uuid field implementations floating around. My favorite one is part of the django_extensions project. It stores uuid's as a 36-character string. But newer PostgreSQL implementations have native support for a uuid column type. Here is a UUIDField implementation (based on the work done by the django_extensions project) that uses a uuid column type in PostgreSQL and char(36) column types in other databases. I have tested dumping and loading data between different databases and it works fine.
Note: I've detected a problem with using inherited models so do not use this as is until I can post a resolution.
import uuid
from django.forms.util import ValidationError
from django import forms
from django.db import models
from django.utils.encoding import smart_unicode
from django.utils.translation import ugettext_lazy
class UUIDVersionError(Exception):
pass
class UUIDField(models.Field):
"""Encode and stores a Python uuid.UUID in a manner that is appropriate
for the given datatabase that we are using.
For sqlite3 or MySQL we save it as a 36-character string value
For PostgreSQL we save it as a uuid field
This class supports type 1, 2, 4, and 5 UUID's.
"""import uuid
from django.forms.util import ValidationError
from django import forms
from django.db import models
from django.utils.encoding import smart_unicode
from django.utils.translation import ugettext_lazy
class UUIDVersionError(Exception):
pass
class UUIDField(models.Field):
"""Encode and stores a Python uuid.UUID in a manner that is appropriate
for the given datatabase that we are using.
For sqlite3 or MySQL we save it as a 36-character string value
For PostgreSQL we save it as a uuid field
This class supports type 1, 2, 4, and 5 UUID's.
"""
__metaclass__ = models.SubfieldBase
_CREATE_COLUMN_TYPES = {
'postgresql_psycopg2': 'uuid',
'postgresql': 'uuid'
}
def __init__(self, verbose_name=None, name=None, auto=True, version=1,
node=None, clock_seq=None, namespace=None, **kwargs):
"""Contruct a UUIDField.
@param verbose_name: Optional verbose name to use in place of what
Django would assign.
@param name: Override Django's name assignment
@param auto: If True, create a UUID value if one is not specified.
@param version: By default we create a version 1 UUID.
@param node: Used for version 1 UUID's. If not supplied, then the
uuid.getnode() function is called to obtain it. This can be slow.
@param clock_seq: Used for version 1 UUID's. If not supplied a random
14-bit sequence number is chosen
@param namespace: Required for version 3 and version 5 UUID's.
@param name: Required for version4 and version 5 UUID's.
See Also:
- Python Library Reference, section 18.16 for more information.
- RFC 4122, "A Universally Unique IDentifier (UUID) URN Namespace"
If you want to use one of these as a primary key for a Django
model, do this::
id = UUIDField(primary_key=True)
This will currently I{not} work with Jython because PostgreSQL support
in Jython is not working for uuid column types.
"""
self.max_length = 36
kwargs['max_length'] = self.max_length
if auto:
kwargs['blank'] = True
kwargs.setdefault('editable', False)
self.auto = auto
self.version = version
if version==1:
self.node, self.clock_seq = node, clock_seq
elif version==3 or version==5:
self.namespace, self.name = namespace, name
super(UUIDField, self).__init__(verbose_name=verbose_name,
name=name, **kwargs)
def create_uuid(self):
if not self.version or self.version==4:
return uuid.uuid4()
elif self.version==1:
return uuid.uuid1(self.node, self.clock_seq)
elif self.version==2:
raise UUIDVersionError("UUID version 2 is not supported.")
elif self.version==3:
return uuid.uuid3(self.namespace, self.name)
elif self.version==5:
return uuid.uuid5(self.namespace, self.name)
else:
raise UUIDVersionError("UUID version %s is not valid." % self.version)
def db_type(self):
from django.conf import settings
return UUIDField._CREATE_COLUMN_TYPES.get(settings.DATABASE_ENGINE,
"char(%s)" % self.max_length)
def to_python(self, value):
"""Return a uuid.UUID instance from the value returned by the
database."""
if not value:
return None
if isinstance(value, uuid.UUID):
return value
# attempt to parse a UUID
return uuid.UUID(smart_unicode(value))
def pre_save(self, model_instance, add):
if self.auto and add:
value = self.create_uuid()
setattr(model_instance, self.attname, value)
else:
value = super(UUIDField, self).pre_save(model_instance, add)
if self.auto and not value:
value = self.create_uuid()
setattr(model_instance, self.attname, value)
return value
def get_db_prep_value(self, value):
"""Casts uuid.UUID values into the format expected by the back end"""
if isinstance(value, uuid.UUID):
return unicode(value)
return value
def value_to_string(self, obj):
val = self._get_val_from_obj(obj)
if val is None:
data = ''
else:
data = unicode(val)
return data
def formfield(self, **kwargs):
defaults = {
'form_class': forms.CharField,
'max_length': self.max_length
}
defaults.update(kwargs)
return super(UUIDField, self).formfield(**defaults)
__metaclass__ = models.SubfieldBase
_CREATE_COLUMN_TYPES = {
'postgresql_psycopg2': 'uuid',
'postgresql': 'uuid'
}
def __init__(self, verbose_name=None, name=None, auto=True, version=1,
node=None, clock_seq=None, namespace=None, **kwargs):
"""Contruct a UUIDField.
@param verbose_name: Optional verbose name to use in place of what
Django would assign.
@param name: Override Django's name assignment
@param auto: If True, create a UUID value if one is not specified.
@param version: By default we create a version 1 UUID.
@param node: Used for version 1 UUID's. If not supplied, then the
uuid.getnode() function is called to obtain it. This can be slow.
@param clock_seq: Used for version 1 UUID's. If not supplied a random
14-bit sequence number is chosen
@param namespace: Required for version 3 and version 5 UUID's.
@param name: Required for version4 and version 5 UUID's.
See Also:
- Python Library Reference, section 18.16 for more information.
- RFC 4122, "A Universally Unique IDentifier (UUID) URN Namespace"
If you want to use one of these as a primary key for a Django
model, do this::
id = UUIDField(primary_key=True)
This will currently I{not} work with Jython because PostgreSQL support
in Jython is not working for uuid column types.
"""
self.max_length = 36
kwargs['max_length'] = self.max_length
if auto:
kwargs['blank'] = True
kwargs.setdefault('editable', False)
self.auto = auto
self.version = version
if version==1:
self.node, self.clock_seq = node, clock_seq
elif version==3 or version==5:
self.namespace, self.name = namespace, name
super(UUIDField, self).__init__(verbose_name=verbose_name,
name=name, **kwargs)
def create_uuid(self):
if not self.version or self.version==4:
return uuid.uuid4()
elif self.version==1:
return uuid.uuid1(self.node, self.clock_seq)
elif self.version==2:
raise UUIDVersionError("UUID version 2 is not supported.")
elif self.version==3:
return uuid.uuid3(self.namespace, self.name)
elif self.version==5:
return uuid.uuid5(self.namespace, self.name)
else:
raise UUIDVersionError("UUID version %s is not valid." % self.version)
def db_type(self):
from django.conf import settings
return UUIDField._CREATE_COLUMN_TYPES.get(settings.DATABASE_ENGINE,
"char(%s)" % self.max_length)
def to_python(self, value):
"""Return a uuid.UUID instance from the value returned by the
database."""
if not value:
return None
if isinstance(value, uuid.UUID):
return value
# attempt to parse a UUID
return uuid.UUID(smart_unicode(value))
def pre_save(self, model_instance, add):
if self.auto and add:
value = self.create_uuid()
setattr(model_instance, self.attname, value)
else:
value = super(UUIDField, self).pre_save(model_instance, add)
if self.auto and not value:
value = self.create_uuid()
setattr(model_instance, self.attname, value)
return value
def get_db_prep_value(self, value):
"""Casts uuid.UUID values into the format expected by the back end"""
if isinstance(value, uuid.UUID):
return unicode(value)
return value
def value_to_string(self, obj):
val = self._get_val_from_obj(obj)
if val is None:
data = ''
else:
data = unicode(val)
return data
def formfield(self, **kwargs):
defaults = {
'form_class': forms.CharField,
'max_length': self.max_length
}
defaults.update(kwargs)
return super(UUIDField, self).formfield(**defaults)
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