mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-15 13:17:24 -04:00
Mike Bayer
3088574414
* major additions to 1.4 migration doc; removed additional verbosity regarding caching methodology and reorganized the doc to present itself more as a "what's changed" guide * as we now have a path for asyncio, update that doc so that we aren't spreading obsolete information * updates to the 2.0 migration guide with latest info, however this is still an architecture doc and not a migration guide yet, will need further rework. * start really talking about 1.x vs. 2.0 style everywhere. Querying is most of the docs so this is going to be a prominent theme, start getting it to fit in * Add introductory documentation for ORM example sections as these are too sparse * new documentation for do_orm_execute(), many separate sections, adding deprecation notes to before_compile() and similar * new example suites to illustrate do_orm_execute(), with_loader_criteria() * modernized horizontal sharding examples and added a separate example to distinguish between multiple databases and single database w/ multiple tables use case * introducing DEEP ALCHEMY, will use zzzeeksphinx 1.1.6 * no name for the alchemist yet however the dragon's name is Flambé Change-Id: Id6b5c03b1ce9ddb7b280f66792212a0ef0a1c541
137 lines
3.6 KiB
Python
137 lines
3.6 KiB
Python
"""Illustrates a custom per-query criteria that will be applied
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to selected entities.
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"""
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import datetime
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from sqlalchemy import Column
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from sqlalchemy import DateTime
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from sqlalchemy import orm
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class HasTemporal(object):
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"""Mixin that identifies a class as having a timestamp column"""
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timestamp = Column(
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DateTime, default=datetime.datetime.utcnow, nullable=False
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)
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def temporal_range(range_lower, range_upper):
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return orm.with_loader_criteria(
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HasTemporal,
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lambda cls: cls.timestamp.between(range_lower, range_upper),
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include_aliases=True,
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)
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if __name__ == "__main__":
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from sqlalchemy import Integer, Column, ForeignKey
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from sqlalchemy import select
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from sqlalchemy import create_engine
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from sqlalchemy.orm import relationship, sessionmaker, selectinload
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from sqlalchemy.ext.declarative import declarative_base
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Base = declarative_base()
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class Parent(HasTemporal, Base):
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__tablename__ = "parent"
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id = Column(Integer, primary_key=True)
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children = relationship("Child")
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class Child(HasTemporal, Base):
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__tablename__ = "child"
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id = Column(Integer, primary_key=True)
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parent_id = Column(Integer, ForeignKey("parent.id"), nullable=False)
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engine = create_engine("sqlite://", echo=True)
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Base.metadata.create_all(engine)
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Session = sessionmaker(bind=engine, future=True)
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sess = Session()
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c1, c2, c3, c4, c5 = [
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Child(timestamp=datetime.datetime(2009, 10, 15, 12, 00, 00)),
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Child(timestamp=datetime.datetime(2009, 10, 17, 12, 00, 00)),
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Child(timestamp=datetime.datetime(2009, 10, 20, 12, 00, 00)),
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Child(timestamp=datetime.datetime(2009, 10, 12, 12, 00, 00)),
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Child(timestamp=datetime.datetime(2009, 10, 17, 12, 00, 00)),
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]
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p1 = Parent(
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timestamp=datetime.datetime(2009, 10, 15, 12, 00, 00),
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children=[c1, c2, c3],
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)
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p2 = Parent(
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timestamp=datetime.datetime(2009, 10, 17, 12, 00, 00),
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children=[c4, c5],
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)
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sess.add_all([p1, p2])
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sess.commit()
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# use populate_existing() to ensure the range option takes
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# place for elements already in the identity map
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parents = (
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sess.query(Parent)
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.populate_existing()
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.options(
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temporal_range(
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datetime.datetime(2009, 10, 16, 12, 00, 00),
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datetime.datetime(2009, 10, 18, 12, 00, 00),
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)
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)
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.all()
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)
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assert parents[0] == p2
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assert parents[0].children == [c5]
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sess.expire_all()
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# try it with eager load
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parents = (
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sess.query(Parent)
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.options(
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temporal_range(
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datetime.datetime(2009, 10, 16, 12, 00, 00),
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datetime.datetime(2009, 10, 18, 12, 00, 00),
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)
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)
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.options(selectinload(Parent.children))
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.all()
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)
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assert parents[0] == p2
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assert parents[0].children == [c5]
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sess.expire_all()
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# illustrate a 2.0 style query
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print("------------------")
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parents = (
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sess.execute(
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select(Parent)
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.execution_options(populate_existing=True)
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.options(
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temporal_range(
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datetime.datetime(2009, 10, 15, 11, 00, 00),
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datetime.datetime(2009, 10, 18, 12, 00, 00),
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)
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)
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.join(Parent.children)
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.filter(Child.id == 2)
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)
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.scalars()
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.all()
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)
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assert parents[0] == p1
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print("-------------------")
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assert parents[0].children == [c1, c2]
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