Function print_function_arguments

src/backend/utils/adt/ruleutils.c:3174–3320

* Common code for pg_get_function_arguments and pg_get_function_result: * append the desired subset of arguments to buf. We print only TABLE * arguments when print_table_args is true, and all the others when it's false. * We print argument defaults only if print_defaults is true. * Function return value is the number of arguments printed. */

 * Function return value is the number of arguments printed.
 */
static int
print_function_arguments(StringInfo buf, HeapTuple proctup,
						 bool print_table_args, bool print_defaults)
{
	Form_pg_proc proc = (Form_pg_proc) GETSTRUCT(proctup);
	int			numargs;
	Oid		   *argtypes;
	char	  **argnames;
	char	   *argmodes;
	int			insertorderbyat = -1;
	int			argsprinted;
	int			inputargno;
	int			nlackdefaults;
	List	   *argdefaults = NIL;
	ListCell   *nextargdefault = NULL;
	int			i;

	numargs = get_func_arg_info(proctup,
								&argtypes, &argnames, &argmodes);

	nlackdefaults = numargs;
	if (print_defaults && proc->pronargdefaults > 0)
	{
		Datum		proargdefaults;
		bool		isnull;

		proargdefaults = SysCacheGetAttr(PROCOID, proctup,
										 Anum_pg_proc_proargdefaults,
										 &isnull);
		if (!isnull)
		{
			char	   *str;

			str = TextDatumGetCString(proargdefaults);
			argdefaults = castNode(List, stringToNode(str));
			pfree(str);
			nextargdefault = list_head(argdefaults);
			/* nlackdefaults counts only *input* arguments lacking defaults */
			nlackdefaults = proc->pronargs - list_length(argdefaults);
		}
	}

	/* Check for special treatment of ordered-set aggregates */
	if (proc->prokind == PROKIND_AGGREGATE)
	{
		HeapTuple	aggtup;
		Form_pg_aggregate agg;

		aggtup = SearchSysCache1(AGGFNOID, proc->oid);
		if (!HeapTupleIsValid(aggtup))
			elog(ERROR, "cache lookup failed for aggregate %u",
				 proc->oid);
		agg = (Form_pg_aggregate) GETSTRUCT(aggtup);
		if (AGGKIND_IS_ORDERED_SET(agg->aggkind))
			insertorderbyat = agg->aggnumdirectargs;
		ReleaseSysCache(aggtup);
	}