Thanks Mike
Unfortunately it seems that after_transaction_end event executes twice:
right before COMMIT and after after_commit event. Here what I see with
echo=True and some prints:
2016-03-29 07:29:14,799 INFO sqlalchemy.engine.base.Engine INSERT INTO
users (id) VALUES (?)
2016-03-29 07:29:14,799 INFO sqlalchemy.engine.base.Engine (3,)
after_transaction_end
2016-03-29 07:29:14,799 INFO sqlalchemy.engine.base.Engine COMMIT
after_commit
after_transaction_end
2016-03-29 07:29:14,800 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
2016-03-29 07:29:14,800 INFO sqlalchemy.engine.base.Engine INSERT INTO
users (id) VALUES (?)
2016-03-29 07:29:14,800 INFO sqlalchemy.engine.base.Engine (2,)
after_transaction_end
2016-03-29 07:29:14,801 INFO sqlalchemy.engine.base.Engine COMMIT
after_commit
after_transaction_end
Consequently the event in after_commit never executes since token is
already set. Here is the complete code:
from sqlalchemy import Column, Integer, create_engine, event
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
engine = create_engine('sqlite:///:memory:', echo=True)
Session = sessionmaker(bind=engine)
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
Base.metadata.create_all(engine)
sess = Session()
sess.add(User(id=1))
sess.commit()
@event.listens_for(sess, 'after_commit')
def foo(session):
print('after_commit')
if "my_token" not in session.info:
print("never called")
@event.listens_for(sess, "after_transaction_end")
def bar(session, transaction):
print('after_transaction_end')
session.info["my_token"] = True
sess.add(User(id=3))
sess.commit()
sess.add(User(id=2))
sess.commit()
On Tuesday, March 29, 2016 at 1:41:32 AM UTC+3, Mike Bayer wrote:
>
>
>
> On 03/28/2016 03:21 PM, Yegor Roganov wrote:
> > I would like to get what I described in the subject: attach an event
> > listener that will execute once after current transaction's successful
> > commit (analogue to django's on_commit
> > <
> https://docs.djangoproject.com/en/1.9/topics/db/transactions/#django.db.transaction.on_commit>
>
> ).
> > If current transaction rolls back, the event listener(s) should be
> > discarded.
>
> set your own token to disable the event after the transaction ends:
>
> @event.listens_for(sess, 'after_commit')
> def foo(session):
> if "my_token" not in session.info:
> print("do my event")
>
>
> @event.listens_for(sess, "after_transaction_end")
> def bar(session, transaction):
> session.info["my_token"] = True
>
>
>
>
> >
> > I have tried using `event.listens_for(sess, 'after_commit', once=True)`,
> > but probably as expected it will execute the callback if session
> > continues to be used after rollback. Here is a complete source that you
> > can play around with:
> > |
> > from sqlalchemy import Column, Integer, create_engine, event
> > from sqlalchemy.orm import sessionmaker
> > from sqlalchemy.ext.declarative import declarative_base
> >
> >
> > Base = declarative_base()
> >
> > engine = create_engine('sqlite:///:memory:', echo=True)
> >
> > Session = sessionmaker(bind=engine)
> >
> >
> > class User(Base):
> > __tablename__ = 'users'
> >
> > id = Column(Integer, primary_key=True)
> >
> > Base.metadata.create_all(engine)
> >
> > sess = Session()
> >
> > sess.add(User(id=1))
> > sess.commit()
> >
> >
> > @event.listens_for(sess, 'after_commit', once=True)
> > def foo(session):
> > print("shouldn't be called since the transaction will be rolled
> back!")
> >
> > sess.add(User(id=1))
> > try:
> > sess.commit()
> > except:
> > sess.rollback()
> >
> > sess.add(User(id=2))
> > sess.commit() # event callback will be called here
> >
> > |
> >
> > There is also an `after_transaction_end` event, but unfortunately I have
> > not managed to bend it to my needs as well: 1) I haven't found public
> > API to determine the transaction state when the callback executes 2) If
> > an event listener is attached in a subtransaction, the callback will get
> > called when the subransaction commits, while I'd like to the callback to
> > only get called when the 'outermost' transaction commits successfully.
> >
> >
> > Greatly appreciate any help.
> >
> > --
> > You received this message because you are subscribed to the Google
> > Groups "sqlalchemy" group.
> > To unsubscribe from this group and stop receiving emails from it, send
> > an email to sqlalchemy+...@googlegroups.com <javascript:>
> > <mailto:sqlalchemy+unsubscr...@googlegroups.com <javascript:>>.
> > To post to this group, send email to sqlal...@googlegroups.com
> <javascript:>
> > <mailto:sqlal...@googlegroups.com <javascript:>>.
> > Visit this group at https://groups.google.com/group/sqlalchemy.
> > For more options, visit https://groups.google.com/d/optout.
>
--
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sqlalchemy+unsubscr...@googlegroups.com.
To post to this group, send email to sqlalchemy@googlegroups.com.
Visit this group at https://groups.google.com/group/sqlalchemy.
For more options, visit https://groups.google.com/d/optout.
