A server crash with a SQL procedure returning a user-defined type on 14.8
Hello there,
I believe I encountered a bug with the following reproduction steps:
CREATE TYPE typ AS (a INT, b INT); CREATE PROCEDURE p_udt(OUT typ) AS $$
SELECT (1, 2); $$ LANGUAGE SQL; CALL p_udt(NULL);
which results in a server crash on version 14.8:
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: WARNING: terminating
connection because of crash of another server process
DETAIL: The postmaster has commanded this server process to roll back the
current transaction and exit, because another server process exited
abnormally and possibly corrupted shared memory.
HINT: In a moment you should be able to reconnect to the database and
repeat your command.
Failed.
Best,
Yahor Yuzefovich
Yahor Yuzefovich <yahor@cockroachlabs.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