Function findRangeSubtypeDiffFunction

src/backend/commands/typecmds.c:2499–2540

}

static Oid
findRangeSubtypeDiffFunction(List *procname, Oid subtype)
{
	Oid			argList[2];
	Oid			procOid;
	AclResult	aclresult;

	/*
	 * Range subtype diff functions must take two arguments of the subtype,
	 * must return float8, and must be immutable.
	 */
	argList[0] = subtype;
	argList[1] = subtype;

	procOid = LookupFuncName(procname, 2, argList, true);

	if (!OidIsValid(procOid))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_FUNCTION),
				 errmsg("function %s does not exist",
						func_signature_string(procname, 2, NIL, argList))));

	if (get_func_rettype(procOid) != FLOAT8OID)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
				 errmsg("range subtype diff function %s must return type %s",
						func_signature_string(procname, 2, NIL, argList),
						"double precision")));

	if (func_volatile(procOid) != PROVOLATILE_IMMUTABLE)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
				 errmsg("range subtype diff function %s must be immutable",
						func_signature_string(procname, 2, NIL, argList))));

	/* Also, range type's creator must have permission to call function */
	aclresult = pg_proc_aclcheck(procOid, GetUserId(), ACL_EXECUTE);
	if (aclresult != ACLCHECK_OK)
		aclcheck_error(aclresult, OBJECT_FUNCTION, get_func_name(procOid));

	return procOid;
}

/*
 *	AssignTypeArrayOid