TableOID in description of inlined function

Hi All,

If I have a table

      create table my_table(id int primary key);

and a function

      create function my_function() returns table(id int) stable as $$ select * from my_table $$ language sql;

then Postgres knows that selecting from the function is really just selecting from the table:


But if you prepare the same select statement and ask Postgres for a description of it, then in the response the column "id" will have a TableOID of 0 - even though we know, on some level, that it's going to be selected straight from a table. I started looking at this because sqlc (https://github.com/sqlc-dev/sqlc) uses TableOID to infer the nullability of the column.

Can someone explain how these two things are connected (or aren't)? Perhaps more importantly, is there a workaround?