mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-07 01:10:52 -04:00
Mike Bayer
98 lines
2.8 KiB
Python
98 lines
2.8 KiB
Python
from sqlalchemy import *
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from sqlalchemy.orm import *
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from sqlalchemy.orm.util import _is_mapped_class
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from sqlalchemy.ext.declarative import declarative_base, declared_attr
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class DeclarativeReflectedBase(object):
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_mapper_args = []
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@classmethod
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def __mapper_cls__(cls, *args, **kw):
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"""Declarative will use this function in lieu of
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calling mapper() directly.
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Collect each series of arguments and invoke
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them when prepare() is called.
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"""
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cls._mapper_args.append((args, kw))
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@classmethod
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def prepare(cls, engine):
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"""Reflect all the tables and map !"""
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while cls._mapper_args:
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args, kw = cls._mapper_args.pop()
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klass = args[0]
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# autoload Table, which is already
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# present in the metadata. This
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# will fill in db-loaded columns
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# into the existing Table object.
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if args[1] is not None:
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table = args[1]
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Table(table.name,
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cls.metadata,
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extend_existing=True,
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autoload_replace=False,
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autoload=True,
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autoload_with=engine,
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schema=table.schema)
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# see if we need 'inherits' in the
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# mapper args. Declarative will have
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# skipped this since mappings weren't
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# available yet.
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for c in klass.__bases__:
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if _is_mapped_class(c):
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kw['inherits'] = c
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break
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klass.__mapper__ = mapper(*args, **kw)
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if __name__ == '__main__':
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Base = declarative_base()
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# create a separate base so that we can
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# define a subset of classes as "Reflected",
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# instead of everything.
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class Reflected(DeclarativeReflectedBase, Base):
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__abstract__ = True
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class Foo(Reflected):
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__tablename__ = 'foo'
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bars = relationship("Bar")
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class Bar(Reflected):
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__tablename__ = 'bar'
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# illustrate overriding of "bar.foo_id" to have
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# a foreign key constraint otherwise not
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# reflected, such as when using MySQL
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foo_id = Column(Integer, ForeignKey('foo.id'))
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e = create_engine('sqlite://', echo=True)
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e.execute("""
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create table foo(
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id integer primary key,
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data varchar(30)
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)
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""")
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e.execute("""
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create table bar(
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id integer primary key,
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data varchar(30),
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foo_id integer
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)
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""")
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Reflected.prepare(e)
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s = Session(e)
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s.add_all([
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Foo(bars=[Bar(data='b1'), Bar(data='b2')], data='f1'),
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Foo(bars=[Bar(data='b3'), Bar(data='b4')], data='f2')
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])
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s.commit()
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for f in s.query(Foo):
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print f.data, ",".join([b.data for b in f.bars]) |