hyphae 1.0.6

Reactive cells and runtime primitives for rship
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142

//! Count-by plan node implementing [`MapQuery`].
//!
//! `count_by` builds an uncompiled plan node that composes with other
//! [`MapQuery`] operators. Call [`MapQuery::materialize`] to compile a plan
//! into a subscribable [`CellMap`](crate::CellMap).

use std::{hash::Hash, marker::PhantomData, sync::Arc};

use crate::{
    map_query::{MapDiffSink, MapQuery, MapQueryInstall},
    subscription::SubscriptionGuard,
    traits::{
        CellValue,
        collections::internal::diff_runtime::{GroupedOps, install_grouped_runtime_via_query},
    },
};

/// Plan node for [`CountByExt::count_by`].
///
/// Groups source rows by the key produced by `group_key(&source_key,
/// &source_value)` and stores how many rows are in each group.
///
/// Not [`Clone`]: cloning a plan would silently duplicate grouping work;
/// share by materializing once.
pub struct CountByPlan<S, K, V, GK, F>
where
    S: MapQuery<K, V>,
    K: Hash + Eq + CellValue,
    V: CellValue,
    GK: Hash + Eq + CellValue,
    F: Fn(&K, &V) -> GK + Send + Sync + 'static,
{
    pub(crate) source: S,
    pub(crate) group_key: Arc<F>,
    pub(crate) _types: PhantomData<fn() -> (K, V, GK)>,
}

impl<S, K, V, GK, F> MapQueryInstall<GK, usize> for CountByPlan<S, K, V, GK, F>
where
    S: MapQuery<K, V>,
    K: Hash + Eq + CellValue,
    V: CellValue,
    GK: Hash + Eq + CellValue,
    F: Fn(&K, &V) -> GK + Send + Sync + 'static,
{
    fn install(self, sink: MapDiffSink<GK, usize>) -> Vec<SubscriptionGuard> {
        let group_key = self.group_key;
        install_grouped_runtime_via_query::<K, V, GK, usize, usize, S, _, _, _, _, _, _>(
            self.source,
            GroupedOps {
                make_group_key: move |k, v| group_key(k, v),
                on_insert: |group_count: &mut usize, _: &K, _: &V| {
                    *group_count += 1;
                },
                on_update: |_: &mut usize, _: &K, _: &V, _: &V| {},
                on_remove: |group_count: &mut usize, _: &K, _: &V| {
                    *group_count = group_count.saturating_sub(1);
                },
                materialize: |group_count: &usize| *group_count,
                is_empty: |group_count: &usize| *group_count == 0,
                new_group_state: || 0usize,
                _marker: std::marker::PhantomData,
            },
            sink,
        )
    }
}

#[allow(private_bounds)]
impl<S, K, V, GK, F> MapQuery<GK, usize> for CountByPlan<S, K, V, GK, F>
where
    S: MapQuery<K, V>,
    K: Hash + Eq + CellValue,
    V: CellValue,
    GK: Hash + Eq + CellValue,
    F: Fn(&K, &V) -> GK + Send + Sync + 'static,
{
}

/// Count-by operator returning a [`MapQuery`] plan node.
///
/// `count_by` consumes `self` and returns an uncompiled plan node; call
/// [`MapQuery::materialize`] on the result to obtain a subscribable
/// [`CellMap`](crate::CellMap).
pub trait CountByExt<K, V>: MapQuery<K, V>
where
    K: Hash + Eq + CellValue,
    V: CellValue,
{
    /// Groups rows by `group_key(&source_key, &source_value)` and stores how
    /// many rows are in each group.
    ///
    /// `group_key` is called for every source row and its return value
    /// becomes the output map key.
    #[track_caller]
    fn count_by<GK, F>(self, group_key: F) -> CountByPlan<Self, K, V, GK, F>
    where
        GK: Hash + Eq + CellValue,
        F: Fn(&K, &V) -> GK + Send + Sync + 'static,
    {
        CountByPlan {
            source: self,
            group_key: Arc::new(group_key),
            _types: PhantomData,
        }
    }
}

impl<K, V, M> CountByExt<K, V> for M
where
    K: Hash + Eq + CellValue,
    V: CellValue,
    M: MapQuery<K, V>,
{
}

#[cfg(test)]
mod tests {
    use std::sync::mpsc;

    use super::*;
    use crate::{CellMap, MapDiff};

    #[test]
    fn count_by_preserves_upstream_batch_without_extra_emissions() {
        let source = CellMap::<String, i32>::new();
        let counts = source.clone().count_by(|_, v| v.to_string()).materialize();

        let (tx, rx) = mpsc::channel::<MapDiff<String, usize>>();
        let _guard = counts.subscribe_diffs(move |diff| {
            let _ = tx.send(diff.clone());
        });

        source.insert_many(vec![("a".to_string(), 1), ("b".to_string(), 2)]);
        let seen: Vec<_> = rx.try_iter().collect();
        assert_eq!(seen.len(), 2);
        match seen.last().unwrap() {
            MapDiff::Batch { changes } => assert_eq!(changes.len(), 2),
            _ => panic!("expected batch diff from count_by"),
        }
    }
}