risingwave_common/row/
slice.rs

1// Copyright 2025 RisingWave Labs
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use std::ops::{Range, RangeBounds};
16
17use super::Row;
18use crate::types::DatumRef;
19
20/// Row for the [`slice`](super::RowExt::slice) method.
21#[derive(Debug, Clone)]
22pub struct Slice<R> {
23    row: R,
24    range: Range<usize>,
25}
26
27impl<R: Row> PartialEq for Slice<R> {
28    fn eq(&self, other: &Self) -> bool {
29        self.iter().eq(other.iter())
30    }
31}
32impl<R: Row> Eq for Slice<R> {}
33
34impl<R: Row> Row for Slice<R> {
35    #[inline]
36    fn datum_at(&self, index: usize) -> DatumRef<'_> {
37        assert!(index < self.len());
38        // SAFETY: we have checked that `self.indices` are all valid in `new`.
39        unsafe { self.row.datum_at_unchecked(self.range.start + index) }
40    }
41
42    #[inline]
43    unsafe fn datum_at_unchecked(&self, index: usize) -> DatumRef<'_> {
44        unsafe { self.row.datum_at_unchecked(self.range.start + index) }
45    }
46
47    #[inline]
48    fn len(&self) -> usize {
49        self.range.len()
50    }
51
52    #[inline]
53    fn iter(&self) -> impl Iterator<Item = DatumRef<'_>> {
54        self.row
55            .iter()
56            .skip(self.range.start)
57            .take(self.range.len())
58    }
59}
60
61impl<R: Row> Slice<R> {
62    pub(crate) fn new(row: R, range: impl RangeBounds<usize>) -> Self {
63        use std::ops::Bound::*;
64        let start = match range.start_bound() {
65            Included(&i) => i,
66            Excluded(&i) => i + 1,
67            Unbounded => 0,
68        };
69        let end = match range.end_bound() {
70            Included(&i) => i + 1,
71            Excluded(&i) => i,
72            Unbounded => row.len(),
73        };
74        let range = start..end;
75        assert!(range.end <= row.len(), "range out of bounds");
76        Self { row, range }
77    }
78}
79
80#[cfg(test)]
81mod tests {
82    use super::*;
83    use crate::row::{OwnedRow, RowExt};
84    use crate::types::{ScalarImpl, ScalarRefImpl};
85
86    #[test]
87    fn test_slice() {
88        let r0 = OwnedRow::new((0..=8).map(|i| Some(ScalarImpl::Int64(i))).collect());
89        let r_expected = OwnedRow::new((2..4).map(|i| Some(ScalarImpl::Int64(i))).collect());
90
91        let r = r0.slice(2..4);
92        assert_eq!(r.len(), 2);
93        assert!(r.iter().eq(r_expected.iter()));
94
95        for i in 0..2 {
96            assert_eq!(r.datum_at(i), Some(ScalarRefImpl::Int64(i as i64 + 2)));
97        }
98    }
99}
risingwave_common/row/slice.rs

risingwave_common/row/
slice.rs
