risingwave_common/row/
project.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::hash::Hash;
16
17use super::Row;
18use crate::types::DatumRef;
19
20/// Row for the [`project`](super::RowExt::project) method.
21#[derive(Debug, Clone, Copy)]
22pub struct Project<'i, R> {
23    row: R,
24    indices: &'i [usize],
25}
26
27impl<R: Row> PartialEq for Project<'_, R> {
28    fn eq(&self, other: &Self) -> bool {
29        self.iter().eq(other.iter())
30    }
31}
32impl<R: Row> Eq for Project<'_, R> {}
33
34impl<R: Row> Row for Project<'_, R> {
35    #[inline]
36    fn datum_at(&self, index: usize) -> DatumRef<'_> {
37        // SAFETY: we have checked that `self.indices` are all valid in `new`.
38        unsafe { self.row.datum_at_unchecked(self.indices[index]) }
39    }
40
41    #[inline]
42    unsafe fn datum_at_unchecked(&self, index: usize) -> DatumRef<'_> {
43        unsafe {
44            self.row
45                .datum_at_unchecked(*self.indices.get_unchecked(index))
46        }
47    }
48
49    #[inline]
50    fn len(&self) -> usize {
51        self.indices.len()
52    }
53
54    #[inline]
55    fn iter(&self) -> impl ExactSizeIterator<Item = DatumRef<'_>> {
56        self.indices
57            .iter()
58            // SAFETY: we have checked that `self.indices` are all valid in `new`.
59            .map(|&i| unsafe { self.row.datum_at_unchecked(i) })
60    }
61}
62
63impl<'i, R: Row> Project<'i, R> {
64    pub(crate) fn new(row: R, indices: &'i [usize]) -> Self {
65        if let Some(index) = indices.iter().find(|&&i| i >= row.len()) {
66            panic!(
67                "index {} out of bounds for row of length {}, row {:?}",
68                index,
69                row.len(),
70                row
71            );
72        }
73        Self { row, indices }
74    }
75
76    pub fn row(&self) -> &R {
77        &self.row
78    }
79}
80
81impl<R: Row> Hash for Project<'_, R> {
82    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
83        self.hash_datums_into(state);
84    }
85}
86
87#[cfg(test)]
88mod tests {
89    use super::*;
90    use crate::row::{OwnedRow, RowExt};
91    use crate::types::{ScalarImpl, ScalarRefImpl};
92
93    #[test]
94    fn test_project_row() {
95        let r0 = OwnedRow::new((0..=8).map(|i| Some(ScalarImpl::Int64(i))).collect());
96        let indices = vec![1, 1, 4, 5, 1, 4];
97
98        let r_expected = OwnedRow::new(
99            indices
100                .iter()
101                .map(|&i| Some(ScalarImpl::Int64(i as _)))
102                .collect(),
103        );
104
105        let r = r0.project(&indices);
106        assert_eq!(r.len(), 6);
107        assert!(r.iter().eq(r_expected.iter()));
108
109        for (i, &v) in indices.iter().enumerate() {
110            assert_eq!(r.datum_at(i), Some(ScalarRefImpl::Int64(v as _)));
111        }
112    }
113}
risingwave_common/row/project.rs

risingwave_common/row/
project.rs
