How to get the total number of rows with a query "limit" ?

Hi

I would like to paginate the results of a query on several pages. So I
use a query with a limit X offset Y to display X results on a page,
ok.

But for the first page, I need to run the same query with a count(*)
to know how many pages I will get (number total of rows/ X).

The problem is my query is very slow (maybe 5s) because there is much
worch to do, and on the first page, I need to run this query twice
(not exactly, but ...) so the page is very very slow to load.

My question is : is there a function to get the total number of rows
even on a query with "limit" ? Or what could I do else ?

Has anybody an idea ?
Thanks for the help
Krystoffff