tustvold commented on code in PR #4609: URL: https://github.com/apache/arrow-rs/pull/4609#discussion_r1280274878
########## arrow-ord/src/rank.rs: ########## @@ -0,0 +1,193 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +use arrow_array::cast::AsArray; +use arrow_array::types::*; +use arrow_array::{downcast_primitive_array, Array, ArrowNativeTypeOp, GenericByteArray}; +use arrow_buffer::NullBuffer; +use arrow_schema::{ArrowError, DataType, SortOptions}; +use std::cmp::Ordering; + +/// Assigns a rank to each value in `array` based on its position in the sorted order +/// +/// Where values are equal, they will be assigned the highest of their ranks, +/// leaving gaps in the overall rank assignment +/// +/// ``` +/// # use arrow_array::StringArray; +/// # use arrow_ord::rank::rank; +/// let array = StringArray::from(vec![Some("foo"), None, Some("foo"), None, Some("bar")]); +/// let ranks = rank(&array, None).unwrap(); +/// assert_eq!(ranks, &[5, 2, 5, 2, 3]); +/// ``` +pub fn rank( + array: &dyn Array, + options: Option<SortOptions>, +) -> Result<Vec<u32>, ArrowError> { + let options = options.unwrap_or_default(); + let ranks = downcast_primitive_array! { + array => primitive_rank(array.values(), array.nulls(), options), + DataType::Utf8 => bytes_rank(array.as_bytes::<Utf8Type>(), options), + DataType::LargeUtf8 => bytes_rank(array.as_bytes::<LargeUtf8Type>(), options), + DataType::Binary => bytes_rank(array.as_bytes::<BinaryType>(), options), + DataType::LargeBinary => bytes_rank(array.as_bytes::<LargeBinaryType>(), options), + d => return Err(ArrowError::ComputeError(format!("{d:?} not supported in rank"))) + }; + Ok(ranks) +} + +fn primitive_rank<T: ArrowNativeTypeOp>( + values: &[T], + nulls: Option<&NullBuffer>, + options: SortOptions, +) -> Vec<u32> { + let len: u32 = values.len().try_into().unwrap(); + let to_sort = match nulls.filter(|n| n.null_count() > 0) { + Some(n) => n + .valid_indices() + .map(|idx| (values[idx], idx as u32)) + .collect(), + None => values.iter().copied().zip(0..len).collect(), + }; + rank_impl(values.len(), to_sort, options, T::compare, T::is_eq) +} + +fn bytes_rank<T: ByteArrayType>( + array: &GenericByteArray<T>, + options: SortOptions, +) -> Vec<u32> { + let to_sort: Vec<(&[u8], u32)> = match array.nulls().filter(|n| n.null_count() > 0) { + Some(n) => n + .valid_indices() + .map(|idx| (array.value(idx).as_ref(), idx as u32)) + .collect(), + None => (0..array.len()) + .map(|idx| (array.value(idx).as_ref(), idx as u32)) + .collect(), + }; + rank_impl(array.len(), to_sort, options, Ord::cmp, PartialEq::eq) +} + +fn rank_impl<T, C, E>( + len: usize, + mut valid: Vec<(T, u32)>, + options: SortOptions, + compare: C, + eq: E, +) -> Vec<u32> +where + T: Copy, + C: Fn(T, T) -> Ordering, + E: Fn(T, T) -> bool, +{ + // We can use an unstable sort as we combine equal values later + valid.sort_unstable_by(|a, b| compare(a.0, b.0)); + if options.descending { + valid.reverse(); + } + + let (mut valid_rank, null_rank) = match options.nulls_first { + true => (len as u32, (len - valid.len()) as u32), + false => (valid.len() as u32, len as u32), + }; + + let mut out: Vec<_> = vec![null_rank; len]; + if let Some(v) = valid.last() { + out[v.1 as usize] = valid_rank; + } + + let mut count = 1; // Number of values in rank + for w in valid.windows(2).rev() { + match eq(w[0].0, w[1].0) { + true => { + count += 1; + out[w[0].1 as usize] = valid_rank; + } + false => { + valid_rank -= count; + count = 1; + out[w[0].1 as usize] = valid_rank + } + } + } + + out +} + +#[cfg(test)] +mod tests { + use super::*; + use arrow_array::*; + + #[test] + fn test_primitive() { + let descending = SortOptions { + descending: true, + nulls_first: true, + }; + + let nulls_last = SortOptions { + descending: false, + nulls_first: false, + }; + + let nulls_last_descending = SortOptions { + descending: true, + nulls_first: false, + }; + + let a = Int32Array::from(vec![Some(1), Some(1), None, Some(3), Some(3), Some(4)]); + let res = rank(&a, None).unwrap(); + assert_eq!(res, &[3, 3, 1, 5, 5, 6]); + + let res = rank(&a, Some(descending)).unwrap(); + assert_eq!(res, &[6, 6, 1, 4, 4, 2]); + + let res = rank(&a, Some(nulls_last)).unwrap(); + assert_eq!(res, &[2, 2, 6, 4, 4, 5]); + + let res = rank(&a, Some(nulls_last_descending)).unwrap(); + assert_eq!(res, &[5, 5, 6, 3, 3, 1]); + + // Test with non-zero null values + let nulls = NullBuffer::from(vec![true, true, false, true, false, false]); + let a = Int32Array::new(vec![1, 4, 3, 4, 5, 5].into(), Some(nulls)); + let res = rank(&a, None).unwrap(); + assert_eq!(res, &[4, 6, 3, 6, 3, 3]); + } + + #[test] + fn test_bytes() { Review Comment: They all fit into the category of byte arrays, they're `GenericByteArray` under the hood -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
