Package: zope.sqlalchemy
IntroductionRunning the testsUsage in shortFull ExampleLong-lasting session scopesDevelopment versionChanges3.1 (2023-09-12)3.0 (2023-06-01)2.0 (2023-02-06)1.6 (2021-09-06)1.5 (2021-07-14)1.4 (2021-04-26)1.3 (2020-02-17)1.2 (2019-10-17)1.1 (2019-01-03)1.0 (2018-01-31)0.7.7 (2016-06-23)0.7.6 (2015-03-20)0.7.5 (2014-06-17)0.7.4 (2014-01-06)0.7.3 (2013-09-25)0.7.2 (2013-02-19)0.7.1 (2012-05-19)0.7 (2011-12-06)0.6.1 (2011-01-08)0.6 (2010-07-24)0.5 (2010-06-07)0.4 (2009-01-20)0.3 (2008-07-29)0.2 (2008-06-28)0.1 (2008-05-15)IntroductionThe aim of this package is to unify the plethora of existing packages
integrating SQLAlchemy with Zope’s transaction management. As such it seeks
only to provide a data manager and makes no attempt to define azopeishway
to configure engines.For WSGI applications, Zope style automatic transaction management is
available withrepoze.tm2(used byTurbogears 2and other systems).This package is also used bypyramid_tm(an add-on of thePyramid) web
framework.You need to understandSQLAlchemyand theZope transaction managerfor
this package and this README to make any sense.Running the testsThis package is distributed as a buildout. Using your desired python run:$ python bootstrap.py
$ ./bin/buildoutThis will download the dependent packages and setup the test script, which may
be run with:$ ./bin/testor with the standard setuptools test command:$ ./bin/py setup.py testTo enable testing with your own database set the TEST_DSN environment variable
to your sqlalchemy database dsn. Two-phase commit behaviour may be tested by
setting the TEST_TWOPHASE variable to a non empty string. e.g:$ TEST_DSN=postgres://test:test@localhost/test TEST_TWOPHASE=True bin/testUsage in shortThe integration between Zope transactions and the SQLAlchemy event system is
done using theregister()function on the session factory class.fromzope.sqlalchemyimportregisterfromsqlalchemyimportcreate_enginefromsqlalchemy.ormimportsessionmaker,scoped_sessionengine=sqlalchemy.create_engine("postgresql://scott:tiger@localhost/test")DBSession=scoped_session(sessionmaker(bind=engine))register(DBSession)Instantiated sessions commits and rollbacks will now be integrated with Zope
transactions.importtransactionfromsqlalchemy.sqlimporttextsession=DBSession()result=session.execute(text("DELETE FROM objects WHERE id=:id"),{"id":2})row=result.fetchone()transaction.commit()Full ExampleThis example is lifted directly from the SQLAlchemy declarative documentation.
First the necessary imports.>>> from sqlalchemy import *
>>> from sqlalchemy.orm import declarative_base, scoped_session, sessionmaker, relationship
>>> from sqlalchemy.sql import text
>>> from zope.sqlalchemy import register
>>> import transactionNow to define the mapper classes.>>> Base = declarative_base()
>>> class User(Base):
...     __tablename__ = 'test_users'
...     id = Column('id', Integer, primary_key=True)
...     name = Column('name', String(50))
...     addresses = relationship("Address", backref="user")
>>> class Address(Base):
...     __tablename__ = 'test_addresses'
...     id = Column('id', Integer, primary_key=True)
...     email = Column('email', String(50))
...     user_id = Column('user_id', Integer, ForeignKey('test_users.id'))Create an engine and setup the tables. Note that for this example to work a
recent version of sqlite/pysqlite is required. 3.4.0 seems to be sufficient.>>> engine = create_engine(TEST_DSN)
>>> Base.metadata.create_all(engine)Now to create the session itself. As zope is a threaded web server we must use
scoped sessions. Zope and SQLAlchemy sessions are tied together by using the
register>>> Session = scoped_session(sessionmaker(bind=engine,
... twophase=TEST_TWOPHASE))Call the scoped session factory to retrieve a session. You may call this as
many times as you like within a transaction and you will always retrieve the
same session. At present there are no users in the database.>>> session = Session()
>>> register(session)
<zope.sqlalchemy.datamanager.ZopeTransactionEvents object at ...>
>>> session.query(User).all()
[]We can now create a new user and commit the changes using Zope’s transaction
machinery, just as Zope’s publisher would.>>> session.add(User(id=1, name='bob'))
>>> transaction.commit()Engine level connections are outside the scope of the transaction integration.>>> engine.connect().execute(text('SELECT * FROM test_users')).fetchall()
[(1, ...'bob')]A new transaction requires a new session. Let’s add an address.>>> session = Session()
>>> bob = session.query(User).all()[0]
>>> str(bob.name)
'bob'
>>> bob.addresses
[]
>>> bob.addresses.append(Address(id=1, email='bob@bob.bob'))
>>> transaction.commit()
>>> session = Session()
>>> bob = session.query(User).all()[0]
>>> bob.addresses
[<Address object at ...>]
>>> str(bob.addresses[0].email)
'bob@bob.bob'
>>> bob.addresses[0].email = 'wrong@wrong'To rollback a transaction, use transaction.abort().>>> transaction.abort()
>>> session = Session()
>>> bob = session.query(User).all()[0]
>>> str(bob.addresses[0].email)
'bob@bob.bob'
>>> transaction.abort()By default, zope.sqlalchemy puts sessions in an ‘active’ state when they are
first used. ORM write operations automatically move the session into a
‘changed’ state. This avoids unnecessary database commits. Sometimes it
is necessary to interact with the database directly through SQL. It is not
possible to guess whether such an operation is a read or a write. Therefore we
must manually mark the session as changed when manual SQL statements write
to the DB.>>> session = Session()
>>> conn = session.connection()
>>> users = Base.metadata.tables['test_users']
>>> conn.execute(users.update().where(users.c.name=='bob'), {'name': 'ben'})
<sqlalchemy.engine... object at ...>
>>> from zope.sqlalchemy import mark_changed
>>> mark_changed(session)
>>> transaction.commit()
>>> session = Session()
>>> str(session.query(User).all()[0].name)
'ben'
>>> transaction.abort()If this is a problem you may register the events and tell them to place the
session in the ‘changed’ state initially.>>> Session.remove()
>>> register(Session, 'changed')
<zope.sqlalchemy.datamanager.ZopeTransactionEvents object at ...>
>>> session = Session()
>>> conn = session.connection()
>>> conn.execute(users.update().where(users.c.name=='ben'), {'name': 'bob'})
<sqlalchemy.engine... object at ...>
>>> transaction.commit()
>>> session = Session()
>>> str(session.query(User).all()[0].name)
'bob'
>>> transaction.abort()Themark_changedfunction accepts a kwarg forkeep_sessionwhich defaults
toFalseand is unaware of the registered extensionskeep_sessionconfiguration.If you intend forkeep_sessionto be True, you can specify it explicitly:>>> from zope.sqlalchemy import mark_changed
>>> mark_changed(session, keep_session=True)
>>> transaction.commit()You can also use a configured extension to preserve this argument:>>> sessionExtension = register(session, keep_session=True)
>>> sessionExtension.mark_changed(session)
>>> transaction.commit()Long-lasting session scopesThe default behaviour of the transaction integration is to close the session
after a commit. You can tell by trying to access an object after committing:>>> bob = session.query(User).all()[0]
>>> transaction.commit()
>>> bob.name
Traceback (most recent call last):
sqlalchemy.orm.exc.DetachedInstanceError: Instance <User at ...> is not bound to a Session; attribute refresh operation cannot proceed...To support cases where a session needs to last longer than a transaction (useful
in test suites) you can specify to keep a session when registering the events:>>> Session = scoped_session(sessionmaker(bind=engine,
... twophase=TEST_TWOPHASE))
>>> register(Session, keep_session=True)
<zope.sqlalchemy.datamanager.ZopeTransactionEvents object at ...>
>>> session = Session()
>>> bob = session.query(User).all()[0]
>>> bob.name = 'bobby'
>>> transaction.commit()
>>> bob.name
'bobby'The session must then be closed manually:>>> session.close()Development versionGIT versionChanges3.1 (2023-09-12)Fixpsycopg.errors.OperationalError.sqlstatecan beNone.
(#81)3.0 (2023-06-01)Add support for SQLAlchemy 2.0 and for new psycopg v3 backend.
(#79)Breaking ChangesNo longer allow callingsession.commit()within a manual nested database
transaction (a savepoint). If you want to use savepoints directly in code that is
not aware oftransaction.savepoint()withsession.begin_nested()then
use the savepoint returned by the function to commit just the nested transaction
i.e.savepoint =session.begin_nested();savepoint.commit()or use it as a
context manager i.e.withsession.begin_nested():.
(for details see #79)2.0 (2023-02-06)Drop support for Python 2.7, 3.5, 3.6.Drop support forSQLAlchemy < 1.1(#65)Add support for Python 3.10, 3.11.1.6 (2021-09-06)Add support for Python 2.7 on SQLAlchemy 1.4.
(#71)1.5 (2021-07-14)Callmark_changedalso on thedo_orm_executeevent if the operation
is an insert, update or delete. This is SQLAlchemy >= 1.4 only, as it
introduced that event.
(#67)Fixup get transaction. There was regression introduced in 1.4.
(#66)1.4 (2021-04-26)Addmark_changedandjoin_transactionmethods toZopeTransactionEvents.
(#46)Reduce DeprecationWarnings with SQLAlchemy 1.4 and require at least
SQLAlchemy >= 0.9.
(#54)Add support for SQLAlchemy 1.4.
(#58)Prevent using an SQLAlchemy 1.4 version with broken flush support.
(#57)1.3 (2020-02-17).datamanager.register()now returns theZopeTransactionEventsinstance which was used to register the events. This allows to change its
parameters afterwards.
(#40)Add preliminary support for Python 3.9a3.1.2 (2019-10-17)Breaking ChangesDrop support for Python 3.4.Add support for Python 3.7 and 3.8.Fix deprecation warnings for the event system. We already used it in general
but still leveraged the old extension mechanism in some places.
(#31)To make things clearer we renamed theZopeTransactionExtensionclass
toZopeTransactionEvents. Existing code using the ‘register’ version
stays compatible.Upgrade from 1.1Your old code like this:fromzope.sqlalchemyimportZopeTransactionExtensionDBSession=scoped_session(sessionmaker(extension=ZopeTransactionExtension(),**options))becomes:fromzope.sqlalchemyimportregisterDBSession=scoped_session(sessionmaker(**options))register(DBSession)1.1 (2019-01-03)Add support to MySQL using pymysql.1.0 (2018-01-31)Add support for Python 3.4 up to 3.6.Support SQLAlchemy 1.2.Drop support for Python 2.6, 3.2 and 3.3.Drop support for transaction < 1.6.0.Fix hazard that could cause SQLAlchemy session not to be committed when
transaction is committed in rare situations.
(#23)0.7.7 (2016-06-23)Support SQLAlchemy 1.1.
(#15)0.7.6 (2015-03-20)Make version check in register compatible with prereleases.0.7.5 (2014-06-17)Ensure mapped objects are expired following atransaction.commit()when
no database commit was required.
(#8)0.7.4 (2014-01-06)Allowsession.commit()on nested transactions to facilitate integration
of existing code that might not usetransaction.savepoint().
(#1)Add a new function zope.sqlalchemy.register(), which replaces the
direct use of ZopeTransactionExtension to make use
of the newer SQLAlchemy event system to establish instrumentation on
the given Session instance/class/factory.   Requires at least
SQLAlchemy 0.7.
(#4)Fixkeep_session=Truedoesn’t work when a transaction is joined by flush
and other manngers bug.
(#5)0.7.3 (2013-09-25)Prevent theSessionobject from getting into a “wedged” state if joining
a transaction fails. With thread scoped sessions that are reused this can cause
persistent errors requiring a server restart.
(#2)0.7.2 (2013-02-19)Make life-time of sessions configurable. Specifykeep_session=Truewhen
setting up the SA extension.Python 3.3 compatibility.0.7.1 (2012-05-19)Use@implementeras a class decorator instead ofimplements()at
class scope for compatibility withzope.interface4.0.  This requireszope.interface>= 3.6.0.0.7 (2011-12-06)Python 3.2 compatibility.0.6.1 (2011-01-08)Update datamanager.mark_changed to handle sessions which have not yet logged
a (ORM) query.0.6 (2010-07-24)Implement should_retry for sqlalchemy.orm.exc.ConcurrentModificationError
and serialization errors from PostgreSQL and Oracle.
(Specify transaction>=1.1 to use this functionality.)Include license files.Addtransaction_managerattribute to data managers for compliance with
IDataManager interface.0.5 (2010-06-07)Remove redundant session.flush() / session.clear() on savepoint operations.
These were only needed with SQLAlchemy 0.4.x.SQLAlchemy 0.6.x support. Require SQLAlchemy >= 0.5.1.Add support for runningpython setup.py test.Pull in pysqlite explicitly as a test dependency.Setup sqlalchemy mappers in test setup and clear them in tear down. This
makes the tests more robust and clears up the global state after. It
caused the tests to fail when other tests in the same run called
clear_mappers.0.4 (2009-01-20)Bugs fixed:Only raise errors in tpc_abort if we have committed.Remove the session id from the SESSION_STATE just before we de-reference the
session (i.e. all work is already successfuly completed). This fixes cases
where the transaction commit failed but SESSION_STATE was already cleared.  In
those cases, the transaction was wedeged as abort would always error.  This
happened on PostgreSQL where invalid SQL was used and the error caught.Call session.flush() unconditionally in tpc_begin.Change error message on session.commit() to be friendlier to non zope users.Feature changes:Support for bulk update and delete with SQLAlchemy 0.5.10.3 (2008-07-29)Bugs fixed:New objects added to a session did not cause a transaction join, so were not
committed at the end of the transaction unless the database was accessed.
SQLAlchemy 0.4.7 or 0.5beta3 now required.Feature changes:For correctness and consistency with ZODB, renamed the function ‘invalidate’
to ‘mark_changed’ and the status ‘invalidated’ to ‘changed’.0.2 (2008-06-28)Feature changes:Updated to support SQLAlchemy 0.5. (0.4.6 is still supported).0.1 (2008-05-15)Initial public release.