exec: support window frames for window functions in vectorized engine

[yuzefovich]

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[yuzefovich]

@DrewKimball I reopened this issue because the already supported window functions also need to be taught about the window frames (e.g. select rank() over (order by a range 1 preceding) from t; is still currently handled by the rowexec windower).

[DrewKimball]

I see. Sounds good

[DrewKimball]

Oh, actually I think we're good to close this after all once first_value, last_value and nth_value are done. Non-aggregate window functions other than first_value, last_value and nth_value seem to all ignore the window frame:

postgres=# select x, y, rank() over (order by y ROWS BETWEEN 1000 FOLLOWING AND 1000 FOLLOWING) from t;
 x |          y          | rank
---+---------------------+------
 1 |                   1 |    1
 4 |                   1 |    1
 5 |                  20 |    3
 3 | 9223372036854775807 |    4
 2 |                     |    5
(5 rows)

Postgres doesn't really have any documentation for this, but here's a relevant quote from MySql docs:

Standard SQL specifies that window functions that operate on the entire partition should have no frame clause. MySQL permits a frame clause for such functions but ignores it. These functions use the entire partition even if a frame is specified:
CUME_DIST()
DENSE_RANK()
LAG()
LEAD()
NTILE()
PERCENT_RANK()
RANK()
ROW_NUMBER()

[yuzefovich]

Oh yeah, I think you're right. We don't look at the frames for those window functions in the row engine either, and I guess we just unnecessarily prohibited frames for them in the vectorized engine.