sqlalchemy uuid for sqlite

uuid_user.py

########################
# UUID for SQLite hack #
########################

from sqlalchemy.types import TypeDecorator, CHAR
from sqlalchemy.dialects.postgresql import UUID
import uuid


class GUID(TypeDecorator):
    """Platform-independent GUID type.

    Uses PostgreSQL's UUID type, otherwise uses
    CHAR(32), storing as stringified hex values.

    """
    impl = CHAR

    def load_dialect_impl(self, dialect):
        if dialect.name == 'postgresql':
            return dialect.type_descriptor(UUID())
        else:
            return dialect.type_descriptor(CHAR(32))

    def process_bind_param(self, value, dialect):
        if value is None:
            return value
        elif dialect.name == 'postgresql':
            return str(value)
        else:
            if not isinstance(value, uuid.UUID):
                return "%.32x" % uuid.UUID(value).int
            else:
                # hexstring
                return "%.32x" % value.int

    def process_result_value(self, value, dialect):
        if value is None:
            return value
        else:
            if not isinstance(value, uuid.UUID):
                value = uuid.UUID(value)
            return value
          
class Base(db.Model):

    __abstract__ = True

    id = db.Column(GUID(), primary_key=True, default=lambda: str(uuid.uuid4()))
    created_at = db.Column(db.DateTime, default=db.func.current_timestamp())
    updated_at = db.Column(db.DateTime,
                    default=db.func.current_timestamp(),
                    onupdate=db.func.current_timestamp())

    
class User(Base):

    __tablename__ = 'users'

    username = db.Column(db.String, nullable=False, unique=True)
    email = db.Column(db.String, nullable=False, unique=True)
    encrypted_password = db.Column(db.String, nullable=False)
    
    def set_password(self, password):
        self.encrypted_password = bc.generate_password_hash(password)

    def verify_password(self, password):
        return bc.check_password_hash(self.encrypted_password, password)

This almost works.
Missing sort_key_function

This is my version:

class GUID(TypeDecorator):
    """Platform-independent GUID type.
    Uses PostgreSQL's UUID type, otherwise uses
    CHAR(32), storing as stringified hex values.
    """

    impl = CHAR
    cache_ok = True

    def load_dialect_impl(self, dialect):
        if dialect.name == "postgresql":
            return dialect.type_descriptor(UUID())
        else:
            return dialect.type_descriptor(CHAR(32))

    def process_bind_param(self, value, dialect):
        if value is None:
            return value
        elif dialect.name == "postgresql":
            return str(value)
        else:
            if not isinstance(value, uuid.UUID):
                return "%.32x" % uuid.UUID(value).int
            else:
                # hexstring
                return "%.32x" % value.int
    
    def _uuid_value(self, value):
        if value is None:
            return value
        else:
            if not isinstance(value, uuid.UUID):
                value = uuid.UUID(value)
            return value         

    def process_result_value(self, value, dialect):
        return self._uuid_value(value)

    def sort_key_function(self, value):
        return self._uuid_value(value)

Awesome! Also you might consider changing the name of process_result_value to something else. :)

Thank you, this was useful!

@splint3rsec: why so? This is needed by SQLAlchemy.

crazy creative workaround. thx for your work!