[Sqlalchemy-tickets] Issue #3083: clarify filter_by() (non-)interaction with select_from() (zzzeek/sqlalchemy)

[Sebastian B. <iss...@bi...>]

New issue 3083: clarify filter_by() (non-)interaction with select_from()
https://bitbucket.org/zzzeek/sqlalchemy/issue/3083/clarify-filter_by-non-interaction-with

Sebastian Bank:

When using `filter_by` to simplify `filter` expressions

    session.query(User).filter(User.id == 1)
    session.query(User).filter_by(id=1)

where `filter_by` applies to the last join entity

    session.query(User).join(user_group).filter(user_group.c.group_id == 5)
    session.query(User).join(user_group).filter_by(group_id=5)
	
I stumbled on the fact that it does not follow a `select_from` (which I expected intuitively):

    session.query(User).select_from(user_group).filter(user_group.c.group_id == 5).join(User)
    session.query(User).select_from(user_group).filter_by(group_id=5).join(User)

The second one fails. In my concrete case, the primary entity actually had an attribute with the same name. Hence, I ended up with the wrong filter condition (discovering that much later).

Maybe a hint in the documentation of `filter_by` and/or `select_from` could help so that others don't make the same mistake.

In the long run, I might also suggest to change this behaviour.