python - sqlalchemy flush() and get inserted id?

Question

I want to do something like this:

f = Foo(bar='x')
session.add(f)
session.flush()

# do additional queries using f.id before commit()
print f.id # should be not None

session.commit()

But f.id is None when I try it. How can I get this to work?

Answer 1

I've just run across the same problem, and after testing I have found that NONE of these answers are sufficient.

Currently, or as of sqlalchemy .6+, there is a very simple solution (I don't know if this exists in prior version, though I imagine it does):

session.refresh()

So, your code would look something like this:

f = Foo(bar=x)
session.add(f)
session.flush()
# At this point, the object f has been pushed to the DB, 
# and has been automatically assigned a unique primary key id

f.id
# is None

session.refresh(f)
# refresh updates given object in the session with its state in the DB
# (and can also only refresh certain attributes - search for documentation)

f.id
# is the automatically assigned primary key ID given in the database.

That's how to do it.