Test d'options relationship(), lazy='dynamic'/'noload', collections en tant...

Test d'options relationship(), lazy='dynamic'/'noload', collections en tant que dictionnaire et non liste

relationship/one_to_many.2.dynamic.py

+"""
+https://docs.sqlalchemy.org/en/14/orm/basic_relationships.html
+
+To establish a bidirectional relationship in one-to-many, where the “reverse” side is a
+many to one, specify an additional relationship() and connect the two using the
+relationship.back_populates parameter.
+"""
+from sqlalchemy import create_engine
+from sqlalchemy import Column, ForeignKey, Integer, String
+from sqlalchemy.orm import declarative_base, relationship
+from sqlalchemy.orm.session import Session
+
+Base = declarative_base()
+
+
+class Parent(Base):
+    __tablename__ = "parent"
+
+    id = Column(Integer, primary_key=True)
+    name = Column(String)
+
+    # A "noload" relationship never loads from the database, even when accessed.
+    # Below, the children collection is fully writeable, and changes to it will
+    # be persisted to the database as well as locally available for reading at
+    # the time they are added.
+    # https://docs.sqlalchemy.org/en/14/orm/collections.html#setting-noload-raiseload
+
+    # MAIS : Normal applications should not have to use "noload" for anything !!!
+    # https://github.com/sqlalchemy/sqlalchemy/discussions/7377
+    children = relationship("Child", lazy="dynamic")
+
+    def __repr__(self):
+        return f"<Parent (name={self.name}, children={self.children})>"
+
+
+class Child(Base):
+    __tablename__ = "child"
+
+    id = Column(Integer, primary_key=True)
+    name = Column(String)
+    parent_id = Column(Integer, ForeignKey("parent.id"))
+
+    def __repr__(self):
+        return f"<Child (name={self.name})>"
+
+
+if __name__ == "__main__":
+    engine = create_engine("sqlite:///one_to_many.2.dynamic.db", echo=False)
+
+    Base.metadata.drop_all(engine)
+    Base.metadata.create_all(engine)
+
+    # cf ../basic-session.1.4.py
+    with Session(engine) as session:
+        jack = Parent(name="Jack")
+
+        alice = Child(name="Alice")
+        john = Child(name="John")
+
+        jack.children = [john, alice]
+
+        with session.begin():
+            session.add(jack)
+            session.add(john)
+            session.add(alice)
+
+            print(jack)
+            # <Parent (name=Jack, children=SELECT child.id AS child_id, child.name AS child_name, child.parent_id AS child_parent_id  # noqa E501
+            # FROM child
+            # WHERE ? = child.parent_id)>
+
+            print(jack.children[:2])
+            # [<Child (name=John)>, <Child (name=Alice)>]
+
+        print(jack)
+        # <Parent (name=Jack, children=SELECT child.id AS child_id, child.name AS child_name, child.parent_id AS child_parent_id  # noqa E501
+        # FROM child
+        # WHERE ? = child.parent_id)>
+
+        print(alice)
+        # <Child (name=Alice)>

relationship/one_to_many.2.noload.py

+"""
+https://docs.sqlalchemy.org/en/14/orm/basic_relationships.html
+
+To establish a bidirectional relationship in one-to-many, where the “reverse” side is a
+many to one, specify an additional relationship() and connect the two using the
+relationship.back_populates parameter.
+"""
+from sqlalchemy import create_engine
+from sqlalchemy import Column, ForeignKey, Integer, String
+from sqlalchemy.orm import declarative_base, relationship
+from sqlalchemy.orm.session import Session
+
+Base = declarative_base()
+
+
+class Parent(Base):
+    __tablename__ = "parent"
+
+    id = Column(Integer, primary_key=True)
+    name = Column(String)
+
+    # A "noload" relationship never loads from the database, even when accessed.
+    # Below, the children collection is fully writeable, and changes to it will
+    # be persisted to the database as well as locally available for reading at
+    # the time they are added.
+    # https://docs.sqlalchemy.org/en/14/orm/collections.html#setting-noload-raiseload
+
+    # MAIS : Normal applications should not have to use "noload" for anything !!!
+    # https://github.com/sqlalchemy/sqlalchemy/discussions/7377
+    children = relationship("Child", lazy="noload")
+
+    def __repr__(self):
+        return f"<Parent (name={self.name}, children={self.children})>"
+
+
+class Child(Base):
+    __tablename__ = "child"
+
+    id = Column(Integer, primary_key=True)
+    name = Column(String)
+    parent_id = Column(Integer, ForeignKey("parent.id"))
+
+    def __repr__(self):
+        return f"<Child (name={self.name})>"
+
+
+if __name__ == "__main__":
+    engine = create_engine("sqlite:///one_to_many.2.noload.db", echo=False)
+
+    Base.metadata.drop_all(engine)
+    Base.metadata.create_all(engine)
+
+    # cf ../basic-session.1.4.py
+    with Session(engine) as session:
+        jack = Parent(name="Jack")
+
+        alice = Child(name="Alice")
+        john = Child(name="John")
+
+        jack.children = [john, alice]
+
+        with session.begin():
+            session.add(jack)
+            session.add(john)
+            session.add(alice)
+
+            print(jack)
+            # <Parent (name=Jack, children=[<Child (name=John)>, <Child (name=Alice)>])>
+
+        print(jack)
+        # <Parent (name=Jack, children=[])>
+        print(alice)
+        # <Child (name=Alice)>

relationship/one_to_many.dictionary.py

+"""
+https://docs.sqlalchemy.org/en/14/orm/basic_relationships.html
+https://docs.sqlalchemy.org/en/14/orm/collections.html#customizing-collection-access
+
+ATTENTION aux changements de la clé du dictionnaire
+https://docs.sqlalchemy.org/en/14/orm/collections.html#dealing-with-key-mutations-and-back-populating-for-dictionary-collections
+"""
+from sqlalchemy import create_engine
+from sqlalchemy import Column, ForeignKey, Integer, String
+from sqlalchemy.orm import declarative_base, relationship
+from sqlalchemy.orm.collections import attribute_mapped_collection
+from sqlalchemy.orm.session import Session
+
+Base = declarative_base()
+
+
+class Item(Base):
+    __tablename__ = "item"
+
+    id = Column(Integer, primary_key=True)
+    notes = relationship(
+        "Note",
+        collection_class=attribute_mapped_collection("keyword"),
+        backref="item",
+        cascade="all, delete-orphan",
+    )
+
+    def __repr__(self):
+        return f"<Item (name={self.id}, notes={self.notes})>"
+
+
+class Note(Base):
+    __tablename__ = "note"
+
+    id = Column(Integer, primary_key=True)
+    keyword = Column(String)
+    text = Column(String)
+
+    item_id = Column(Integer, ForeignKey("item.id"))
+
+    def __repr__(self):
+        return f"<Node (keyword={self.keyword}, text={self.text})>"
+
+
+if __name__ == "__main__":
+    engine = create_engine("sqlite:///one_to_many.dictionary.db", echo=False)
+
+    Base.metadata.drop_all(engine)
+    Base.metadata.create_all(engine)
+
+    # cf ../basic-session.1.4.py
+    with Session(engine) as session:
+        item = Item()
+        n1 = Note(keyword="a", text="atext")
+        n1.item = item
+        n2 = Note(keyword="b", text="btext")
+        n2.item = item
+
+        with session.begin():
+            session.add(item)
+            session.add(n1)
+            session.add(n2)
+
+        print(item)
+        # <Item (name=1, notes={'a': <Node (keyword=a, text=atext)>, 'b': <Node (keyword=b, text=btext)>})>  # noqa E501
+
+        print(n1)
+        # <Node (keyword=a, text=atext)>