Major Description
Sometimes, filter compares the rank-like window functions with number.
SELECT *, ROW_NUMBER() OVER(ORDER BY a) AS rn FROM Tab1 WHERE rn <= 5
We can create a Limit(5) and push down it as the child of Window.
SELECT *, ROW_NUMBER() OVER(ORDER BY a) AS rn FROM (SELECT * FROM Tab1 ORDER BY a LIMIT 5) t
