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 <to...@benchling.com > <javascript:>> 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 <to...@benchling.com> 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 sqlal...@googlegroups.com. > >> > To post to this group, send email to sqlal...@googlegroups.com. > >> > 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 sqlal...@googlegroups.com <javascript:>. > > To post to this group, send email to sqlal...@googlegroups.com > <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/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. 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