Dear all,
I am currently working on implementing UUID as primary keys in my database.
I have come across an issue that I cannot find an explanation for: using
the `sqlalchemy.Uuid` type in declarative mapping yields different results
at initialization. I sometimes get the following error:
*"The type provided inside the 'id' attribute Mapped annotation is the
SQLAlchemy type <class 'sqlalchemy.sql.sqltypes.Uuid'>. Expected a Python
type instead"*
I have a Caregiver table, for which id is a PostgreSQL UUID, and a Match
Event table holding 2 fields which use the Caregiver id as foreign key.
Those 2 fields are PostgreSQL UUID as well.
If my classes definitions are as follow, the initialization runs smoothly,
as well as inserts in the Match Event table:
from sqlalchemy import (
ForeignKey,
Uuid,
)
from sqlalchemy.orm import (
Mapped,
mapped_column,
relationship,
)
class MatchEventOrm(Base):
__tablename__ = "match_event"
id: Mapped[int] = mapped_column(primary_key=True)
subject_caregiver_id: Mapped[Uuid] = mapped_column(
ForeignKey("caregiver.id")
)
object_caregiver_id: Mapped[Uuid] = mapped_column(
ForeignKey("caregiver.id")
)
subject_caregiver: Mapped["CaregiverOrm"] = relationship(
back_populates="match_event_subject_of",
foreign_keys=[subject_caregiver_id],
)
object_caregiver: Mapped["CaregiverOrm"] = relationship(
back_populates="match_event_object_of",
foreign_keys=[object_caregiver_id],
)
class CaregiverOrm(Base):
__tablename__ = "caregiver"
id: Mapped[*str*] = mapped_column(primary_key=True)
uid: Mapped[str]
user_email: Mapped[str]
...
However, if I change to the following:
from sqlalchemy import (
ForeignKey,
Uuid,
)
from sqlalchemy.orm import (
Mapped,
mapped_column,
relationship,
)
class MatchEventOrm(Base):
__tablename__ = "match_event"
id: Mapped[int] = mapped_column(primary_key=True)
subject_caregiver_id: Mapped[Uuid] = mapped_column(
ForeignKey("caregiver.id")
)
object_caregiver_id: Mapped[Uuid] = mapped_column(
ForeignKey("caregiver.id")
)
subject_caregiver: Mapped["CaregiverOrm"] = relationship(
back_populates="match_event_subject_of",
foreign_keys=[subject_caregiver_id],
)
object_caregiver: Mapped["CaregiverOrm"] = relationship(
back_populates="match_event_object_of",
foreign_keys=[object_caregiver_id],
)
class CaregiverOrm(Base):
__tablename__ = "caregiver"
id: Mapped[*Uuid*] = mapped_column(primary_key=True)
uid: Mapped[str]
user_email: Mapped[str]
...
I get the aforementioned error message.
I may be using type annotations wrong, any insight on what I am doing wrong
would be welcome.
Thanks a lot for your support.
Regards,
Pierre
--
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The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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