if OrderBy list contains the expr that doesn't exist in Select list?

[fzhedu]

T1(a int,b int,c int)
select a from T1 order by b+c;

should wo change the processing strcture?
@wangli1426,@egraldlo
or wo can solve this problen later?

[wangli1426]

In my opinion, it seems that the current processing structure is fine.
The order operator cannot change the schema, but the project operator can. Hence, the generated logical tree to the mentioned query should be like this:

Scan(T1)->Project(a,b,c,b+c)->Order(b+c)->Project(a,b,c)

@fzhedu: Anyhow, this problem can be solved later.