I have a large number (around a dozen or more, and likely to grow) of derived classes, so I was hoping to cut down repetition with the @declared_attr. So, 3rd (or farther) derived classes need the inherit_condition to point to their immediate base. That does seem to remove the warning.
On 9/3/20 9:58 AM, Mike Bayer wrote: > you might be able to use the declared_attr __mapper__ but you would > need to omit that erroneous inherit condition if the class is > "Name". IMO it would be easier to follow and understand by simply > using explicit __mapper_args__ on each class but this depends on what > you're doing. > > > > On Thu, Sep 3, 2020, at 7:24 AM, Richard Damon wrote: >> I've tried taking my code and changing the ForeignKey to be to Node, and >> that doesn't change the Warning. >> Is the problem trying to DRY with the @declared_attr __mapper__? >> >> On 9/2/20 11:29 PM, Mike Bayer wrote: >> > well you are giving Name an inherit condition that conflicts with how >> > you set up the foreign key. >> > >> > Name.node_id FKs to Property.node_id >> > >> > but then inherit condition is Name.node_id -> Node.node_id >> > >> > There seems to be a little unsmoothness to actually being able to >> > configure it that way, that is, skipping over Property.node_id, but in >> > this case your FKs make it clear what you're going for which is the >> > "normal' setup of Name->Property->Node so you can remove "inherit >> > condition" from Name and it works fine: >> > >> > class Name(Property): >> > __tablename__ = 'Name' >> > >> > node_id = Column(Integer, ForeignKey("Property.node_id"), >> > primary_key=True) >> > >> > __mapper_args__ = { >> > "polymorphic_identity": "Name", >> > } >> > >> > >> > or set it: >> > >> > class Name(Property): >> > __tablename__ = 'Name' >> > >> > node_id = Column(Integer, ForeignKey("Property.node_id"), >> > primary_key=True) >> > >> > __mapper_args__ = { >> > "polymorphic_identity": "Name", >> > "inherit_condition": node_id == Property.node_id, >> > } >> > >> > >> > >> > On Wed, Sep 2, 2020, at 10:08 PM, Richard Damon wrote: >> >> Here is the code, note in all cases node_id are foreign >> key/primary_key >> >> to a primary_key down the chain: >> >> >> >> >> >> class Base: >> >> """Base Class for SQLAlchemy ORM Classes""" >> >> @declared_attr >> >> def __tablename__(cls): >> >> """Default the Table Name to the Class Name""" >> >> return cls.__name__ >> >> >> >> Base = declarative_base(cls=Base) >> >> >> >> class Node(Base): >> >> """Class repesents the base of the User Data types.""" >> >> node_id = Column(Integer, primary_key=True) >> >> type_name = Column(String(255), nullable=False) # todo should >> come >> >> from type_id >> >> >> >> @declared_attr >> >> def __mapper_args__(cls): >> >> if cls.__name__ == 'Node' : >> >> __mapper_args__ = { >> >> 'polymorphic_identity': 'Node', >> >> 'polymorphic_on': cls.type_name, >> >> } >> >> else: >> >> __mapper_args__ = { >> >> 'polymorphic_identity': cls.__tablename__, >> >> "inherit_condition": cls.node_id == Node.node_id >> >> } >> >> return __mapper_args__ >> >> >> >> class Property(Node): >> >> node_id = Column(Integer, ForeignKey('Node.node_id'), >> >> primary_key=True) >> >> ref_id = Column(Integer, ForeignKey('Node.node_id')) >> >> >> >> class Name(Property): >> >> node_id = Column(Integer, ForeignKey('Property.node_id'), >> >> primary_key=True) >> >> >> >> >> >> On 9/2/20 9:39 PM, Mike Bayer wrote: >> >> > there's an FAQ entry, a little bit dated but the general idea is >> still >> >> > there, at: >> >> > >> >> >> > >> >https://docs.sqlalchemy.org/en/13/faq/ormconfiguration.html#i-m-getting-a-warning-or-error-about-implicitly-combining-column-x-under-attribute-y >> >> > >> >> > for joined table inheritance, where Name(Node) -> node_id are FK -> >> >> > PK, the warning isn't emitted. so please share the mapping if it is >> >> > doing this when it shouldnt. >> >> > >> >> > >> >> > On Wed, Sep 2, 2020, at 9:08 PM, Richard Damon wrote: >> >> >> I am getting the following error: >> >> >> >> >> >> SAWarning: Implicitly combining column Node.node_id with column >> >> >> Name.node_id under attribute 'node_id'. Please configure one >> or more >> >> >> attributes for these same-named columns explicitly. >> >> >> >> >> >> In my case I am using poymorphic classes by joining with the >> ORM. Node >> >> >> is the base of the hierarchy (derived from declarative_base), >> then I >> >> >> have a class Property derived from it, and a class Name derived >> from >> >> >> Property. Each class has a primary_key named node_id, with a >> >> foreign key >> >> >> constraint one step done the hierarchy. I have also tried making >> >> all the >> >> >> Foreign key constraints point to Node.node_id and it doesn't make a >> >> >> difference. >> >> >> >> >> >> It is just a warning, and the lookup does seem to make the double >> >> join, >> >> >> so it doesn't seem to be a big problem, but it seems it want me to >> >> >> configure something for these, but I am not sure what. >> >> >> >> >> >> Two level inheritance is working just fine, it is just where it >> >> hits the >> >> >> 3rd level that it seems to want something explicit. >> >> >> >> >> >> -- >> >> >> Richard Damon >> >> >> >> >> >> -- >> >> Richard Damon >> >> -- >> Richard Damon >> >> -- >> SQLAlchemy - >> The Python SQL Toolkit and Object Relational Mapper >> >> http://www.sqlalchemy.org/ >> >> To post example code, please provide an MCVE: Minimal, Complete, and >> Verifiable Example. See http://stackoverflow.com/help/mcve for a >> full description. >> --- >> You received this message because you are subscribed to the Google >> Groups "sqlalchemy" group. >> To unsubscribe from this group and stop receiving emails from it, >> send an email to sqlalchemy+unsubscr...@googlegroups.com >> <mailto:sqlalchemy+unsubscr...@googlegroups.com>. >> To view this discussion on the web >> visit >> https://groups.google.com/d/msgid/sqlalchemy/290a226a-60b7-a3e3-70de-85ec47b7c142%40Damon-Family.org. >> > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google > Groups "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send > an email to sqlalchemy+unsubscr...@googlegroups.com > <mailto:sqlalchemy+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/1a45c6d0-f85f-440a-af1f-47fa9b254e5b%40www.fastmail.com > <https://groups.google.com/d/msgid/sqlalchemy/1a45c6d0-f85f-440a-af1f-47fa9b254e5b%40www.fastmail.com?utm_medium=email&utm_source=footer>. -- Richard Damon -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. 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