Class CircularDependencyError

lib/sqlalchemy/exc.py:212–252

Raised by topological sorts when a circular dependency is detected. There are two scenarios where this error occurs: * In a Session flush operation, if two objects are mutually dependent on each other, they can not be inserted or deleted via INSERT or DELETE statements alone; a

class CircularDependencyError(SQLAlchemyError):
    """Raised by topological sorts when a circular dependency is detected.

    There are two scenarios where this error occurs:

    * In a Session flush operation, if two objects are mutually dependent
      on each other, they can not be inserted or deleted via INSERT or
      DELETE statements alone; an UPDATE will be needed to post-associate
      or pre-deassociate one of the foreign key constrained values.
      The ``post_update`` flag described at :ref:`post_update` can resolve
      this cycle.
    * In a :attr:`_schema.MetaData.sorted_tables` operation, two
      :class:`_schema.ForeignKey`
      or :class:`_schema.ForeignKeyConstraint` objects mutually refer to each
      other.  Apply the ``use_alter=True`` flag to one or both,
      see :ref:`use_alter`.

    """

    def __init__(
        self,
        message: str,
        cycles: Any,
        edges: Any,
        msg: Optional[str] = None,
        code: Optional[str] = None,
    ):
        if msg is None:
            message += " (%s)" % ", ".join(repr(s) for s in cycles)
        else:
            message = msg
        SQLAlchemyError.__init__(self, message, code=code)
        self.cycles = cycles
        self.edges = edges

    def __reduce__(self) -> Union[str, Tuple[Any, ...]]:
        return (
            self.__class__,
            (None, self.cycles, self.edges, self.args[0]),
            {"code": self.code} if self.code is not None else {},
        )


class CompileError(SQLAlchemyError):