Size a linked open data set

Hello

In my work, I need to know the number of distinct resources in a dataset.
For example, with dbpedia-fr, I'm trying
select count(distinct ?r) where { ?r ?p ?l }

And I'm always getting a timeout error message
While with
select count(?r) where { ?r ?p ?l }
I'm getting
185404575

Is it a good way to know about such size?

--
Jean-Claude Moissinac