RE: Window functions speed

Where's the query? Are you able to run explain analyze so we can see estimates vs actual counts? What version are you using?

Can you share explain analyze before and after the window function? 

I mean, that limit at the top makes me think it is doing a lot less work without the window function, vs examining all candidate rows if we need to count them all. What are you using that count for anyway? Pagination?

Based on the hint here. We looked at the query and found most of the culprits were with a param that forced all accessible records – it should not have been there in most cases. We have removed that for most users and its fine !