differential_dogs3/operators/
count.rs

1use timely::dataflow::Scope;
2
3use differential_dataflow::{ExchangeData, VecCollection, Hashable};
4use differential_dataflow::difference::{Semigroup, Monoid, Multiply};
5use differential_dataflow::operators::arrange::Arranged;
6use differential_dataflow::trace::TraceReader;
7
8/// Reports a number of extensions to a stream of prefixes.
9///
10/// This method takes as input a stream of `(prefix, count, index)` triples.
11/// For each triple, it extracts a key using `key_selector`, and finds the
12/// associated count in `arrangement`. If the found count is less than `count`,
13/// the `count` and `index` fields are overwritten with their new values.
14pub fn count<G, Tr, K, R, F, P>(
15    prefixes: &VecCollection<G, (P, usize, usize), R>,
16    arrangement: Arranged<G, Tr>,
17    key_selector: F,
18    index: usize,
19) -> VecCollection<G, (P, usize, usize), R>
20where
21    G: Scope<Timestamp=Tr::Time>,
22    Tr: TraceReader<KeyOwn = K, Time: std::hash::Hash, Diff=isize>+Clone+'static,
23    for<'a> Tr::Diff : Semigroup<Tr::DiffGat<'a>>,
24    K: Hashable + Ord + Default + 'static,
25    R: Monoid+Multiply<Output = R>+ExchangeData,
26    F: Fn(&P)->K+Clone+'static,
27    P: ExchangeData,
28{
29    crate::operators::lookup_map(
30        prefixes,
31        arrangement,
32        move |p: &(P,usize,usize), k: &mut K| { *k = key_selector(&p.0); },
33        move |(p,c,i), r, _, s| {
34            let s = *s as usize;
35            if *c < s { ((p.clone(), *c, *i), r.clone()) }
36            else      { ((p.clone(), s, index), r.clone()) }
37        },
38        Default::default(),
39        Default::default(),
40        Default::default(),
41    )
42}
differential_dogs3/operators/count.rs

differential_dogs3/operators/
count.rs
