On Thu, 19 Aug 2021 at 00:20, Andy Fan <zhihui.fan1...@gmail.com> wrote: > In the current master, the result is: > > empno | salary | c | dr > -------+--------+---+---- > 8 | 6000 | 4 | 1
> In the patched version， the result is: > > empno | salary | c | dr > -------+--------+---+---- > 8 | 6000 | 1 | 1 Thanks for taking it for a spin. That's a bit unfortunate. I don't immediately see how to fix it other than to restrict the optimisation to only apply when there's a single WindowClause. It might be possible to relax it further and only apply if it's the final window clause to be evaluated, but in those cases, the savings are likely to be much less anyway as some previous WindowAgg will have exhausted all rows from its subplan. Likely restricting it to only working if there's 1 WindowClause would be fine as for the people using row_number() for a top-N type query, there's most likely only going to be 1 WindowClause. Anyway, I'll take a few more days to think about it before posting a fix. David
