Re: A server crash with a SQL procedure returning a user-defined type on 14.8

Yahor Yuzefovich <yahor(at)cockroachlabs(dot)com> writes:
> CREATE TYPE typ AS (a INT, b INT); CREATE PROCEDURE p_udt(OUT typ) AS $$
> SELECT (1, 2); $$ LANGUAGE SQL; CALL p_udt(NULL);

Thanks for the report. What seems to be happening is that functions.c
is getting confused as to whether it should return a record containing
a record, or just a record. check_sql_fn_retval explains:

* If the target list has one non-junk entry, and that expression has
* or can be coerced to the declared return type, take it as the
* result. This allows, for example, 'SELECT func2()', where func2
* has the same composite return type as the function that's calling
* it. This provision creates some ambiguity --- maybe the expression
* was meant to be the lone field of the composite result --- but it
* works well enough as long as we don't get too enthusiastic about
* inventing coercions from scalar to composite types.

As far as I know, that is fine for functions. But it's not fine for
procedures: those are marked as returning RECORD if there are any
output parameters at all, and the code for CALL expects that it's
going to get back a record containing one column per output parameter,
so we can't flatten that into a record containing two ints.
This has been busted since we invented procedures, I think.

This is easy to fix if we add a parameter to check_sql_fn_retval
indicating whether we're considering a function or a procedure.
While that's not problematic in HEAD, I'm worried that there might
be external callers of that function in the back branches. I guess
we can use the old trick of making the existing function into a
wrapper in the back branches.

regards, tom lane