Function window_first_value

src/backend/utils/adt/windowfuncs.c:406–420

* first_value * return the value of VE evaluated on the first row of the * window frame, per spec. */

 * window frame, per spec.
 */
Datum
window_first_value(PG_FUNCTION_ARGS)
{
	WindowObject winobj = PG_WINDOW_OBJECT();
	Datum		result;
	bool		isnull;

	result = WinGetFuncArgInFrame(winobj, 0,
								  0, WINDOW_SEEK_HEAD, true,
								  &isnull, NULL);
	if (isnull)
		PG_RETURN_NULL();

	PG_RETURN_DATUM(result);
}

/*
 * last_value