On 4/22/23 14:14, Tatsuo Ishii wrote:
I revisited the thread:
https://www.postgresql.org/message-id/flat/CAGMVOdsbtRwE_4%2Bv8zjH1d9xfovDeQAGLkP_B6k69_VoFEgX-A%40mail.gmail.com
and came up with attached POC patch (I used some varibale names
appearing in the Krasiyan Andreev's patch). I really love to have
RESPECT/IGNORE NULLS because I believe they are convenient for
users.
Excellent. I was thinking about picking my version of this patch up
again, but I think this might be better than mine.
I am curious why set_mark is false in the IGNORE version instead of also
being const_offset. Surely the nth non-null in the frame will never go
backwards.
Dealing with marks was the main reason (I think) that my patch was not
accepted.
For FIRST/LAST I am not so excited since there are alternatives
as our document stats,
I disagree with this. The point of having FROM LAST is to avoid
calculating a new window and running a new pass over it.
> so FIRST/LAST are not included in the patch.
I do agree that we can have <null treatment> without <from first or
last> so let's move forward with this and handle the latter later.
Currently in the patch only nth_value is allowed to use RESPECT/IGNORE
NULLS.
This should not be hard coded. It should be a new field in pg_proc
(with a sanity check that it is only true for window functions). That
way custom window functions can implement it.
I think it's not hard to implement it for others (lead, lag,
first_value and last_value).
It doesn't seem like it should be, no.
No document nor test patches are included for now.
I can volunteer to work on these if you want.
Note that RESPECT/IGNORE are not registered as reserved keywords in
this patch (but registered as unreserved keywords). I am not sure if
this is acceptable or not.
For me, this is perfectly okay. Keep them at the lowest level of
reservation as possible.
--
Vik Fearing
