Re: BUG #19732: first_value/last_value/nth_value return NULL with EXCLUDE TIES when the current row is outside its f

Hi Andrey,

v2 looks good, I checked first_value, last_value and nth_value
against array_agg for every frame shape, and they all match now.

Maybe one more test

SELECT k, first_value(k) OVER w
FROM (VALUES (0), (1), (1), (1), (2)) t(k)
WINDOW w AS (ORDER BY k ROWS BETWEEN 2 FOLLOWING AND UNBOUNDED FOLLOWING
EXCLUDE TIES);

On Master it report ERROR: cannot fetch row before WindowObject's mark
position

This patch also covers 19731

Thanks,
Shihao