gistfile1.py

# UUIDField - a strictly binary, filterable, efficient UUID field that works with MySQL, PostgreSQL, SQLite3
# Needs a lot more testing. Current version not tested on PostgreSQL. Partially based on David Cramer's
# UUIDField, with ideas taken from django-extensions, django's BinaryField and some other places.
import uuid

from django import forms
from django.db.models import Field, SubfieldBase

# Enable native UUIDs in PostgreSQL (from dcramer/django-uuidfield)
try:
    import psycopg2.extras
    psycopg2.extras.register_uuid()
except (ImportError, AttributeError):
    pass

# Tell SQlite to not convert uuids into strings.
try:
    try:
        from pysqlite2 import dbapi2 as SQLiteDatabase
    except ImportError:
        from sqlite3 import dbapi2 as SQLiteDatabase
except ImportError:
    pass

if SQLiteDatabase:
    SQLiteDatabase.register_converter("uuid", lambda s: s)

class UUIDField(Field):    
    description = "UUID field"
    __metaclass__ = SubfieldBase

    def __init__(self, auto=False, *args, **kwargs):
        kwargs['max_length'] = 16
        self.auto = auto
        super(UUIDField, self).__init__(*args, **kwargs)

    def pre_save(self, model_instance, add):
        value = getattr(model_instance, self.attname, None)
        if self.auto and add and not value:
            uuid_ = uuid.uuid4().bytes
            setattr(model_instance, self.attname, uuid_)
            value = uuid_
        return value

    def db_type(self, connection):
        if connection and ('postgres' in connection.vendor or 'sqlite' in connection.vendor):
                return 'uuid'
        return 'binary(16)'

    def get_db_prep_value(self, value, connection, prepared=False):
        if value is None:
            return None
        return connection.Database.Binary(value)

    def value_to_string(self, obj):
        if obj:
            value = self._get_val_from_obj(obj)
            return value
        return None

    def to_python(self, value):
        # PostgreSQL is really smart and handles our UUIDs natively. But,
        # to keep it simple, we just mash down to bytes.
        if isinstance(value, uuid.UUID):
            return value.bytes
        return value

# For south migrations (from dcramer/django-uuidfield)
# Need to edit this for your usage.
try:
    from south.modelsinspector import add_introspection_rules
    add_introspection_rules([], [r"^app\.fields\.UUIDField"])
except ImportError:
    pass