mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-14 12:47:22 -04:00
Mike Bayer
cfd5b3e78f
* requirements needs typing_extensions * update all "future=True" references to be appropriate to 2.0 Change-Id: I2eeb0ae65afdb587f21aeb0020f1d8a292f67c21
137 lines
3.5 KiB
Python
137 lines
3.5 KiB
Python
"""Illustrates a custom per-query criteria that will be applied
|
|
to selected entities.
|
|
|
|
|
|
"""
|
|
|
|
import datetime
|
|
|
|
from sqlalchemy import Column
|
|
from sqlalchemy import DateTime
|
|
from sqlalchemy import orm
|
|
|
|
|
|
class HasTemporal:
|
|
"""Mixin that identifies a class as having a timestamp column"""
|
|
|
|
timestamp = Column(
|
|
DateTime, default=datetime.datetime.utcnow, nullable=False
|
|
)
|
|
|
|
|
|
def temporal_range(range_lower, range_upper):
|
|
return orm.with_loader_criteria(
|
|
HasTemporal,
|
|
lambda cls: cls.timestamp.between(range_lower, range_upper),
|
|
include_aliases=True,
|
|
)
|
|
|
|
|
|
if __name__ == "__main__":
|
|
|
|
from sqlalchemy import Integer, Column, ForeignKey
|
|
from sqlalchemy import select
|
|
from sqlalchemy import create_engine
|
|
from sqlalchemy.orm import relationship, sessionmaker, selectinload
|
|
from sqlalchemy.ext.declarative import declarative_base
|
|
|
|
Base = declarative_base()
|
|
|
|
class Parent(HasTemporal, Base):
|
|
__tablename__ = "parent"
|
|
id = Column(Integer, primary_key=True)
|
|
children = relationship("Child")
|
|
|
|
class Child(HasTemporal, Base):
|
|
__tablename__ = "child"
|
|
id = Column(Integer, primary_key=True)
|
|
parent_id = Column(Integer, ForeignKey("parent.id"), nullable=False)
|
|
|
|
engine = create_engine("sqlite://", echo=True)
|
|
Base.metadata.create_all(engine)
|
|
|
|
Session = sessionmaker(bind=engine)
|
|
|
|
sess = Session()
|
|
|
|
c1, c2, c3, c4, c5 = [
|
|
Child(timestamp=datetime.datetime(2009, 10, 15, 12, 00, 00)),
|
|
Child(timestamp=datetime.datetime(2009, 10, 17, 12, 00, 00)),
|
|
Child(timestamp=datetime.datetime(2009, 10, 20, 12, 00, 00)),
|
|
Child(timestamp=datetime.datetime(2009, 10, 12, 12, 00, 00)),
|
|
Child(timestamp=datetime.datetime(2009, 10, 17, 12, 00, 00)),
|
|
]
|
|
|
|
p1 = Parent(
|
|
timestamp=datetime.datetime(2009, 10, 15, 12, 00, 00),
|
|
children=[c1, c2, c3],
|
|
)
|
|
p2 = Parent(
|
|
timestamp=datetime.datetime(2009, 10, 17, 12, 00, 00),
|
|
children=[c4, c5],
|
|
)
|
|
|
|
sess.add_all([p1, p2])
|
|
sess.commit()
|
|
|
|
# use populate_existing() to ensure the range option takes
|
|
# place for elements already in the identity map
|
|
|
|
parents = (
|
|
sess.query(Parent)
|
|
.populate_existing()
|
|
.options(
|
|
temporal_range(
|
|
datetime.datetime(2009, 10, 16, 12, 00, 00),
|
|
datetime.datetime(2009, 10, 18, 12, 00, 00),
|
|
)
|
|
)
|
|
.all()
|
|
)
|
|
|
|
assert parents[0] == p2
|
|
assert parents[0].children == [c5]
|
|
|
|
sess.expire_all()
|
|
|
|
# try it with eager load
|
|
parents = (
|
|
sess.query(Parent)
|
|
.options(
|
|
temporal_range(
|
|
datetime.datetime(2009, 10, 16, 12, 00, 00),
|
|
datetime.datetime(2009, 10, 18, 12, 00, 00),
|
|
)
|
|
)
|
|
.options(selectinload(Parent.children))
|
|
.all()
|
|
)
|
|
|
|
assert parents[0] == p2
|
|
assert parents[0].children == [c5]
|
|
|
|
sess.expire_all()
|
|
|
|
# illustrate a 2.0 style query
|
|
print("------------------")
|
|
parents = (
|
|
sess.execute(
|
|
select(Parent)
|
|
.execution_options(populate_existing=True)
|
|
.options(
|
|
temporal_range(
|
|
datetime.datetime(2009, 10, 15, 11, 00, 00),
|
|
datetime.datetime(2009, 10, 18, 12, 00, 00),
|
|
)
|
|
)
|
|
.join(Parent.children)
|
|
.filter(Child.id == 2)
|
|
)
|
|
.scalars()
|
|
.all()
|
|
)
|
|
|
|
assert parents[0] == p1
|
|
print("-------------------")
|
|
assert parents[0].children == [c1, c2]
|