Hello, I got stuck on a problem related to relatioships and cascades. In the docs <http://docs.sqlalchemy.org/en/latest/orm/cascades.html>, we have the following explanation:
Cascades: *Mappers support the concept of configurable cascade behavior on relationship() <http://docs.sqlalchemy.org/en/latest/orm/relationship_api.html#sqlalchemy.orm.relationship> constructs. This refers to how operations performed on a “parent” object relative to a particular Session <http://docs.sqlalchemy.org/en/latest/orm/session_api.html#sqlalchemy.orm.session.Session> should be propagated to items referred to by that relationship (e.g. “child” objects), and is affected by the relationship.cascade <http://docs.sqlalchemy.org/en/latest/orm/relationship_api.html#sqlalchemy.orm.relationship.params.cascade> option.* It seems to me that the cascade attribute works only in the parent->child direction. Right now, I'm trying to figure out how to create one child with its parent_id, followed by an automatic refresh of its parent children list (i.e. without appending the child to the parent children list). Maybe it is not a good practice to use parent ids in ORM, but I'm wondering if it is possible to do it so. Sometimes we only want to create a child to a parent_id, without loading the parent object. Let me show the source code that reproduce my problem: from sqlalchemy import Table, Column, Integer, String, ForeignKey from sqlalchemy.orm import relationship, backref, sessionmaker from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import create_engine Base = declarative_base() Base = declarative_base() class Parent(Base): __tablename__ = 'parent' parent_id = Column(Integer, primary_key=True) children = relationship("Child", back_populates="parent", cascade="all") class Child(Base): __tablename__ = 'child' child_id = Column(Integer, primary_key=True) name = Column(String) parent_id = Column(Integer, ForeignKey('parent.parent_id')) parent = relationship("Parent", back_populates="children", cascade="all") engine = create_engine('sqlite:///:memory:', echo=False) Session = sessionmaker(bind=engine) Session.configure(bind=engine) Base.metadata.create_all(engine) s = Session() p = Parent() c1 = Child(name="C1") p.children.append(c1) s.add(p) s.flush() print([x.name for x in p.children]) # ['C1'] c2 = Child(parent_id=1, name="C2") s.add(c2) s.flush() print([x.name for x in p.children]) # ['C1'] s.refresh(c2.parent) # This solves my problem, but I would like to know how to do it automatically without an explicit refresh print([x.name for x in p.children]) # ['C1','C2'] s.close() In this code, when I create child "C2" pointing it to parent_id=1, the parent object (children relationship) is not refreshed automatically. So, it only prints the first child: C1. After the refresh, I see both children C1 and C2. Is there any option that refresh the parent authomatically? Is there anything that I'm missing? Thanks! Edans Sandes -- 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. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
