vortex_array/arrays/chunked/compute/
is_constant.rs

1// SPDX-License-Identifier: Apache-2.0
2// SPDX-FileCopyrightText: Copyright the Vortex contributors
3
4use vortex_error::{VortexExpect, VortexResult};
5
6use crate::arrays::{ChunkedArray, ChunkedVTable};
7use crate::compute::{IsConstantKernel, IsConstantKernelAdapter, IsConstantOpts, is_constant_opts};
8use crate::{Array, register_kernel};
9
10impl IsConstantKernel for ChunkedVTable {
11    fn is_constant(
12        &self,
13        array: &ChunkedArray,
14        opts: &IsConstantOpts,
15    ) -> VortexResult<Option<bool>> {
16        let mut chunks = array.non_empty_chunks();
17
18        let first_chunk = chunks
19            .next()
20            .vortex_expect("Must have at least one non-empty chunk");
21
22        match is_constant_opts(first_chunk, opts)? {
23            // Un-determined
24            None => return Ok(None),
25            Some(false) => return Ok(Some(false)),
26            Some(true) => {}
27        }
28
29        let first_value = first_chunk.scalar_at(0)?.into_nullable();
30
31        for chunk in chunks {
32            match is_constant_opts(chunk, opts)? {
33                // Un-determined
34                None => return Ok(None),
35                Some(false) => return Ok(Some(false)),
36                Some(true) => {}
37            }
38
39            if first_value != chunk.scalar_at(0)?.into_nullable() {
40                return Ok(Some(false));
41            }
42        }
43
44        Ok(Some(true))
45    }
46}
47
48register_kernel!(IsConstantKernelAdapter(ChunkedVTable).lift());
49
50#[cfg(test)]
51mod tests {
52    use vortex_buffer::{Buffer, buffer};
53    use vortex_dtype::{DType, Nullability, PType};
54
55    use crate::arrays::ChunkedArray;
56    use crate::{Array, IntoArray};
57
58    #[test]
59    fn empty_chunk_is_constant() {
60        let chunked = ChunkedArray::try_new(
61            vec![
62                Buffer::<u8>::empty().into_array(),
63                Buffer::<u8>::empty().into_array(),
64                buffer![255u8, 255].into_array(),
65                Buffer::<u8>::empty().into_array(),
66                buffer![255u8, 255].into_array(),
67            ],
68            DType::Primitive(PType::U8, Nullability::NonNullable),
69        )
70        .unwrap()
71        .into_array();
72
73        assert!(chunked.statistics().compute_is_constant().unwrap());
74    }
75}
vortex_array/arrays/chunked/compute/is_constant.rs

vortex_array/arrays/chunked/compute/
is_constant.rs
