Ohh I see thanks for the help! And just to confirm on the onupdate front, is it not possible to return the current value of the object being updated? It's ok to emit an extraneous update if the value doesn't change.
On Wednesday, May 15, 2019 at 5:30:06 PM UTC-7, Mike Bayer wrote: > > On Wed, May 15, 2019 at 6:10 PM Tony Cao <[email protected] > <javascript:>> wrote: > > > > I mean query.update(). > > > > Ah our goal was to make it so the update in question happened > automatically without the developer having to explicitly specify it - in > that case both obj.attr = x and obj_class.query.update({obj.attr: x}) > should both trigger an update to obj.attr_modified. That's why I initially > asked about onupdate, as it is triggered for both cases. > > > for query.update() you can use the before_compile_update() and modify > the context.values dictionary in place to affect the UPDATE statement > generated by query.update(). See > > https://docs.sqlalchemy.org/en/13/orm/events.html?highlight=before_compile_update#sqlalchemy.orm.events.QueryEvents.before_compile_update. > > > Additional detail regarding .values will be up within 30 minutes. > > > > > > > > On Wednesday, May 15, 2019 at 2:38:19 PM UTC-7, Mike Bayer wrote: > >> > >> Bulk query updates, you mean, query.update() ? Or > >> session.bulk_update_mappings() ? In both cases you are > >> programatically providing the VALUES clause, so you know from your own > >> data what the UPDATE statement will be. > >> > >> > >> > >> On Wed, May 15, 2019 at 4:14 PM Tony Cao <[email protected]> wrote: > >> > > >> > Ah but it also looks like the before_update event isn't triggered > when doing bulk query updates, which we'd like to also update on. Is there > a way to track those? > >> > > >> > On Wednesday, May 15, 2019 at 10:38:24 AM UTC-7, Mike Bayer wrote: > >> >> > >> >> you can inspect() the object and look at > inspect(obj).attrs['some_attr'].history > >> >> > >> >> > https://docs.sqlalchemy.org/en/13/orm/internals.html#sqlalchemy.orm.state.AttributeState > > >> >> > >> >> > >> >> On Wed, May 15, 2019 at 1:14 PM Tony Cao <[email protected]> > wrote: > >> >> > > >> >> > Hi, > >> >> > > >> >> > Thanks for the response! I also tried looking into before_update, > but is there a recommended way to figure out what columns are being updated > from that event? I had found this post ( > https://stackoverflow.com/questions/15642286/how-can-i-get-a-sqlalchemy-orm-objects-previous-state-after-a-db-update) > > that suggests looking at the history of the attribute state - is there a > better way? > >> >> > > >> >> > On Wednesday, May 15, 2019 at 7:55:44 AM UTC-7, Mike Bayer wrote: > >> >> >> > >> >> >> On Mon, May 13, 2019 at 4:18 PM Tony Cao <[email protected]> > wrote: > >> >> >> > > >> >> >> > Hi all, > >> >> >> > > >> >> >> > Is there way to use Column.onupdate conditionally? For example, > say I have: > >> >> >> > > >> >> >> > class A(Base): > >> >> >> > foo = Column(String) > >> >> >> > bar = Column(String) > >> >> >> > foo_updated = Column(DateTime, onupdate=update_fn) # Should > only update when foo is updated > >> >> >> > > >> >> >> > def update_fn(context): > >> >> >> > if ...: # How can I check if only foo was updated? > >> >> >> > return datetime.now() > >> >> >> > else: > >> >> >> > return ... # How can I say to not update? > >> >> >> > > >> >> >> > Is there a way to define update_fn to only update foo_updated > when foo changes? I can look at context.get_current_parameters() to see > what columns are being used in the compiled statement, but it doesn't > explicitly say which columns are the ones actually being updated; for > example, if I have > >> >> >> > > >> >> >> > A.query.filter(A.bar == 'test').update({A.foo: 'new'}, > synchronize_session=False) > >> >> >> > > >> >> >> > then context.get_current_parameters will return a dict with > keys for both 'bar' and 'foo', although it looks like it suffixes the > filter param with a '_1' - is that something I can rely on to know if a > column is used as a filter instead of an update? And beyond that, is there > a way I can specify to not update the column? > >> >> >> > > >> >> >> > Alternatively, is there another approach recommended to doing > this? > >> >> >> > >> >> >> the most common way is to use the ORM level before_update event: > >> >> >> > >> >> >> > https://docs.sqlalchemy.org/en/13/orm/events.html?highlight=before_update#sqlalchemy.orm.events.MapperEvents.before_update > > >> >> >> > >> >> >> there's also before_execute() at the Core level, but before the > UPDATE > >> >> >> statement is even written, e.g. at the ORM level, is the best > way. > >> >> >> Once you are in the onupdate Python function, you have to return > a > >> >> >> value, as this occurs well after the UPDATE statement has been > >> >> >> compiled. > >> >> >> > >> >> >> > >> >> >> > >> >> >> > >> >> >> > > >> >> >> > Thanks! > >> >> >> > > >> >> >> > -- > >> >> >> > 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 [email protected]. > >> >> >> > To post to this group, send email to [email protected]. > > >> >> >> > Visit this group at https://groups.google.com/group/sqlalchemy. > > >> >> >> > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/b66e89c9-6618-4600-9381-182fa101f5b6%40googlegroups.com. > > > >> >> >> > 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 [email protected]. > >> >> > To post to this group, send email to [email protected]. > >> >> > Visit this group at https://groups.google.com/group/sqlalchemy. > >> >> > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/f13c4205-1df5-49c5-8c91-3c97cd8d9b05%40googlegroups.com. > > > >> >> > 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 [email protected]. > >> > To post to this group, send email to [email protected]. > >> > Visit this group at https://groups.google.com/group/sqlalchemy. > >> > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/38b1162d-1204-41b7-9649-3938775eeef8%40googlegroups.com. > > > >> > 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 [email protected] <javascript:>. > > To post to this group, send email to [email protected] > <javascript:>. > > Visit this group at https://groups.google.com/group/sqlalchemy. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/6dfe0cd9-c55c-486a-94b0-85eb222bdb55%40googlegroups.com. > > > > 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/sqlalchemy. To view this discussion on the web visit https://groups.google.com/d/msgid/sqlalchemy/1151a938-bcce-4d16-ba18-d2e489af7af3%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
