Mike - Thanks for such a great explanation. It is truly appreciated. -Jim
On Fri, Feb 8, 2019 at 4:53 PM Mike Bayer <mike...@zzzcomputing.com> wrote: > changes to attributes are only significant until the next flush > occurs. flushing is described at : > https://docs.sqlalchemy.org/en/latest/orm/session_basics.html#flushing. > When flush() happens, the changes to your attributes are pushed out > to the database, and the history is erased. This is because the > system only supports a "current" a "previous" value, it is only > designed to suit the purposes of session.flush(), which is to show how > the attribute differs from what is known to be in the database (in > this sense it's really not "history", it's just, "whats in the DB > right now?"). > > An important aspect to flushing is that the Session automatically > flushes before each query. This is called autoflush. if you want > to look at things that are affected by the flush occurring, you need > to turn it off. the docs above illustrate you can set > session.autoflush = False, but there is also a context manager that > may be more useful; the above documentation will include the link to > this manager in the next ten minutes, however it looks like: > > with session.no_autoflush: > myobject.foo = bar > session.query(MyObject).all() > inspect(myobject).attrs.foo.history > > direct docs for no_autoflush: > > https://docs.sqlalchemy.org/en/latest/orm/session_api.html?highlight=no_autoflush#sqlalchemy.orm.session.Session.no_autoflush > > > > > > On Fri, Feb 8, 2019 at 3:22 PM Jim S <ato.st...@gmail.com> wrote: > > > > Hi > > > > Newbie here. I think I have a fundamental misunderstanding of either > how session works or you inspect works. My goal is to track changes to my > object. I wrote up this sample to show what I'm having trouble > understanding. > > > > from sqlalchemy import create_engine, inspect > > from sqlalchemy import Column, BigInteger, String, Date, Integer > > from sqlalchemy.ext.declarative import declarative_base > > from sqlalchemy.orm import sessionmaker > > > > from dateutil.relativedelta import * > > > > Base = declarative_base() > > > > > > class SaTest(Base): > > __tablename__ = 'sa_test' > > > > id = Column(BigInteger, primary_key=True) > > name = Column(String(50)) > > dob = Column(Date) > > number_of_children = Column(Integer) > > > > def __repr__(self): > > return self.name > > > > > > engine = create_engine('mysql://mysqluser:mysqlpassword@servername > /databasename') > > Base.metadata.bind = engine > > > > DBSession = sessionmaker(bind=engine) > > session = DBSession() > > > > """ > > # run this the first time to create the data > > jim = SaTest(name='Jim', dob=parse('1971-02-23'), number_of_children=3) > > session.add(jim) > > > > joe = SaTest(name='Joe', dob=parse('1968-06-09'), number_of_children=5) > > session.add(joe) > > > > session.commit() > > """ > > > > jim = session.query(SaTest).filter_by(id=1).one() > > jim.dob = jim.dob + relativedelta(days=+14) > > jim.number_of_children = jim.number_of_children + 1 > > > > #joe = session.query(SaTest).filter_by(id=2).first() <---- if I > uncomment this line, inspect doesn't display the changes in history > > > > insp = inspect(jim) > > > > for attr, attr_state in insp.attrs.items(): > > if attr_state.history.has_changes(): > > print('{}: {}'.format(attr, attr_state.value)) > > print('History: {}\n'.format(attr_state.history)) > > > > > > I've built this based on the example at the bottom of page 107 in the > O'Reilly Essential SQLAlchemy book. > > > > It seems to my that running the second query is somehow invalidating the > inspection of the jim object. I'd really like to understand why, but > haven't been able to find anything to help explain it to me. > > > > Any help would really be appreciated. > > > > -Jim > > > > -- > > SQLAlchemy - > > The Python SQL Toolkit and Object Relational Mapper > > > > http://www.sqlalchemy.org/ > > > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > > --- > > 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. > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to a topic in the > Google Groups "sqlalchemy" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/sqlalchemy/P7iQBRipcXg/unsubscribe. > To unsubscribe from this group and all its topics, 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. > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- 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.
