Rel8 equivalent of `SELECT *, COUNT(*) OVER () FROM ... LIMIT n`

[evertedsphere]

I have a fairly expensive Rel8 select of the form SELECT * FROM ... LIMIT n OFFSET k. (I'll elide the OFFSET, since it doesn't change anything below.)

In addition to fetching a subset of the rows using a LIMIT, I'd like to also fetch the total number of qualifying rows, which in SQL I would do as follows:

SELECT *, COUNT(*) OVER () 
FROM ... 
LIMIT n

I'm not sure how to do COUNT(*) OVER () in Rel8 in the first place. Window appears to be for window function-based queries, not windows in the WINDOW w AS ... sense, and Partitions can only be used to modify Windows as far as I can tell from the API.

Given that there doesn't seem to be any support for non-MATERIALIZED CTEs either, I'm also not sure how to express this query in the usual alternative manner where one puts the query in a CTE and then selects from it twice (WITH cte AS (...) SELECT * FROM (SELECT count(*) FROM cte) LEFT JOIN (TABLE cte ORDER BY ... LIMIT n) ON true).

Certainly I could do

newQuery = do
  q <- offset 5 $ limit 5 oldQuery
  ct <- countStar oldQuery
  pure (ct, q)

and I suspect this will produce the right output, but I'm not sure it's idiomatic for Rel8.