Can ORM object attributes be computed by a TextClause at add time

[ArsenArsen]

Hi!

For very unfortunate reasons, I have some complex ID assigning logic implemented in SQL.
Can this logic be added to a transient ORM object just before a Session#add?
This roughly looks as follows:

obj = ORMObject()
obj.obj_id = text("1 + 2")
db.session.add(obj)

The above appears to work, but fails to type-check: error: Incompatible types in assignment (expression has type "TextClause", variable has type "SQLCoreOperations[int] | int") [assignment].

Is this supported?

TIA

PS: I realized just a bit ago that I can probably use the query builder rather than a text() clause, and that might type-check, but when I originally asked on Gerrit, I was asked to post a discussion also. Will try to query-build now. (EDIT: could query-build and it type checks.. leaving discussion open just in case as the above seems supported but not properly typed)

[zzzeek]

this pattern is fine, to deal w/ the typing use literal_column() instead of text(), the former is more appropriate for a SQL expression written as textual SQL that resolves to a single value.

[ArsenArsen]

heh, perhaps I oversimplified in the example above.

the real usage was more like text("some_fun(:a, :b)").bindparams(bindparam("a", foo, unique=True), bindparam("b", bar, unique=True)) (which, I then realized, was perfectly possible to implement via the query builder completely without text clauses)

the bindparams made it so that I needed a text clause (AFAICT, I can't bind into a literal)

[zzzeek]

if it's just a function then use func.some_fun("a", "b"), that's a lot easier

[ArsenArsen]

if it's just a function then use func.some_fun("a", "b"), that's a lot easier

yes, I did; I replaced the text clause with a nice query builder invocation that was well-typed, but I've been asked (on gitter) to also open a discussion to evaluate the type error, given that the text clause can't appear to pass the type check but does appear to work

[zzzeek]

the text() thing is usually going to work almost anywhere, but for a column expression the literal_column() is more appropriate. but if you have the bound parameters in there, there's not a good pattern for that right now, maybe text(..).columns(Integer).scalar_subquery()

[ArsenArsen]

this appears to work: text("").columns(foo=Integer()).scalar_subquery()

thanks! (but, yes, I ended up just using func in the end)