Efficient way to get size of a graph?

[KonradHoeffner]

Is counting the iterator graph.triples().count() the correct way to get the size of a graph or is there another way?
Right now I only load very small turtle files but I'm worried that when users of my application load let's say a 500 MB Turtle file, that Rust manually going through each item in the iterator may cause a delay, or is that not an issue?

[pchampin]

If you are writing generic code, where the only thing you know about graph is that it implements the Graph trait, then:

• If you need an exact count, yes, graph.triples().count() is the way to go.
• If you can make do with an estimation, graph.triples().size_hint() will be cheaper.

The rationale is that the Graph trait might be implemented by types that can not cheaply determine the exact number of triples.

If, on the other hand, you know the precise type of graph, then you might have other options:

• for all graphs in sophia::inmem (FastGraph, LightGraph), the result of graph.triples().size_hint() will always be strictly accurate (min=max).
• Vec<T> and HashSet<T> implement Graph if T implements Triple; obviously, with those, you can use their len() method.