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
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179

use crate::docset::{DocSet, SkipResult};
use crate::query::Scorer;
use crate::DocId;
use crate::Score;

#[derive(Clone, Copy, Debug)]
enum State {
    ExcludeOne(DocId),
    Finished,
}

/// Filters a given `DocSet` by removing the docs from a given `DocSet`.
///
/// The excluding docset has no impact on scoring.
pub struct Exclude<TDocSet, TDocSetExclude> {
    underlying_docset: TDocSet,
    excluding_docset: TDocSetExclude,
    excluding_state: State,
}

impl<TDocSet, TDocSetExclude> Exclude<TDocSet, TDocSetExclude>
where
    TDocSetExclude: DocSet,
{
    /// Creates a new `ExcludeScorer`
    pub fn new(
        underlying_docset: TDocSet,
        mut excluding_docset: TDocSetExclude,
    ) -> Exclude<TDocSet, TDocSetExclude> {
        let state = if excluding_docset.advance() {
            State::ExcludeOne(excluding_docset.doc())
        } else {
            State::Finished
        };
        Exclude {
            underlying_docset,
            excluding_docset,
            excluding_state: state,
        }
    }
}

impl<TDocSet, TDocSetExclude> Exclude<TDocSet, TDocSetExclude>
where
    TDocSet: DocSet,
    TDocSetExclude: DocSet,
{
    /// Returns true iff the doc is not removed.
    ///
    /// The method has to be called with non strictly
    /// increasing `doc`.
    fn accept(&mut self) -> bool {
        let doc = self.underlying_docset.doc();
        match self.excluding_state {
            State::ExcludeOne(excluded_doc) => {
                if doc == excluded_doc {
                    false
                } else if excluded_doc > doc {
                    true
                } else {
                    match self.excluding_docset.skip_next(doc) {
                        SkipResult::OverStep => {
                            self.excluding_state = State::ExcludeOne(self.excluding_docset.doc());
                            true
                        }
                        SkipResult::End => {
                            self.excluding_state = State::Finished;
                            true
                        }
                        SkipResult::Reached => false,
                    }
                }
            }
            State::Finished => true,
        }
    }
}

impl<TDocSet, TDocSetExclude> DocSet for Exclude<TDocSet, TDocSetExclude>
where
    TDocSet: DocSet,
    TDocSetExclude: DocSet,
{
    fn advance(&mut self) -> bool {
        while self.underlying_docset.advance() {
            if self.accept() {
                return true;
            }
        }
        false
    }

    fn skip_next(&mut self, target: DocId) -> SkipResult {
        let underlying_skip_result = self.underlying_docset.skip_next(target);
        if underlying_skip_result == SkipResult::End {
            return SkipResult::End;
        }
        if self.accept() {
            underlying_skip_result
        } else if self.advance() {
            SkipResult::OverStep
        } else {
            SkipResult::End
        }
    }

    fn doc(&self) -> DocId {
        self.underlying_docset.doc()
    }

    /// `.size_hint()` directly returns the size
    /// of the underlying docset without taking in account
    /// the fact that docs might be deleted.
    fn size_hint(&self) -> u32 {
        self.underlying_docset.size_hint()
    }
}

impl<TScorer, TDocSetExclude> Scorer for Exclude<TScorer, TDocSetExclude>
where
    TScorer: Scorer,
    TDocSetExclude: DocSet + 'static,
{
    fn score(&mut self) -> Score {
        self.underlying_docset.score()
    }
}

#[cfg(test)]
mod tests {

    use super::*;
    use crate::postings::tests::test_skip_against_unoptimized;
    use crate::query::VecDocSet;
    use crate::tests::sample_with_seed;

    #[test]
    fn test_exclude() {
        let mut exclude_scorer = Exclude::new(
            VecDocSet::from(vec![1, 2, 5, 8, 10, 15, 24]),
            VecDocSet::from(vec![1, 2, 3, 10, 16, 24]),
        );
        let mut els = vec![];
        while exclude_scorer.advance() {
            els.push(exclude_scorer.doc());
        }
        assert_eq!(els, vec![5, 8, 15]);
    }

    #[test]
    fn test_exclude_skip() {
        test_skip_against_unoptimized(
            || {
                Box::new(Exclude::new(
                    VecDocSet::from(vec![1, 2, 5, 8, 10, 15, 24]),
                    VecDocSet::from(vec![1, 2, 3, 10, 16, 24]),
                ))
            },
            vec![1, 2, 5, 8, 10, 15, 24],
        );
    }

    #[test]
    fn test_exclude_skip_random() {
        let sample_include = sample_with_seed(10_000, 0.1, 1);
        let sample_exclude = sample_with_seed(10_000, 0.05, 2);
        let sample_skip = sample_with_seed(10_000, 0.005, 3);
        test_skip_against_unoptimized(
            || {
                Box::new(Exclude::new(
                    VecDocSet::from(sample_include.clone()),
                    VecDocSet::from(sample_exclude.clone()),
                ))
            },
            sample_skip,
        );
    }

}