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new 6ea6c12189 MINOR: add complete lexsort_to_indices usage example
(#11133)
6ea6c12189 is described below
commit 6ea6c12189ed8e5e632fd3280d42f40ac4a7cede
Author: Wilhelm Ågren <[email protected]>
AuthorDate: Tue Sep 22 15:37:28 2026 +0200
MINOR: add complete lexsort_to_indices usage example (#11133)
# Which issue does this PR close?
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enhancements and this helps us generate change logs for our releases.
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No open issue.
# Rationale for this change
<!--
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in the issue then this section is not needed.
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your changes and offer better suggestions for fixes.
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I had issues finding complete examples of sorting a record batch with
multiple columns, and others might encounter the same issue.
It was not clear to me how to lexicographically sort a record batch
using `lexsort_to_indices`. The docs mention converting to row form as a
potentially faster alternative for sorting over many columns, but the
current docs for `lexsort_to_indices` does not show how the row indices
in the returned `UInt32Array` might be used.
# What changes are included in this PR?
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is sometimes worth providing a summary of the individual changes in this
PR.
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Adds an example in the docs for how to use `lexsort_to_indices` together
with `take_record_batch` to sort a `RecordBatch` by multiple cols.
# Are these changes tested?
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Yes, `cargo test -p arrow-ord --doc`
# Are there any user-facing changes?
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Docs only.
---------
Co-authored-by: Andrew Lamb <[email protected]>
---
arrow-ord/src/sort.rs | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/arrow-ord/src/sort.rs b/arrow-ord/src/sort.rs
index c2629245bf..f56c972ae0 100644
--- a/arrow-ord/src/sort.rs
+++ b/arrow-ord/src/sort.rs
@@ -934,6 +934,42 @@ pub fn lexsort(columns: &[SortColumn], limit:
Option<usize>) -> Result<Vec<Array
/// Sort elements lexicographically from a list of `ArrayRef` into an unsigned
integer
/// (`UInt32Array`) of indices.
///
+/// # Example
+///
+/// ```
+/// # use std::sync::Arc;
+/// # use arrow_array::{ArrayRef, UInt32Array, Int32Array, RecordBatch,
StringArray};
+/// # use arrow_ord::sort::{lexsort_to_indices, SortColumn};
+/// # use arrow_select::take::take_record_batch;
+/// // Two columns (a, b). Values (2,x), (1, z), (1(a))
+/// let batch = RecordBatch::try_from_iter(vec![
+/// ("a", Arc::new(Int32Array::from(vec![2, 1, 1])) as ArrayRef),
+/// ("b", Arc::new(StringArray::from(vec!["x", "z", "a"])) as ArrayRef),
+/// ])
+/// .unwrap();
+///
+/// // Configure sort by (a, b)
+/// let sort_columns = vec![
+/// SortColumn {
+/// values: batch.column(0).clone(),
+/// options: None,
+/// },
+/// SortColumn {
+/// values: batch.column(1).clone(),
+/// options: None,
+/// },
+/// ];
+///
+/// // indices of the rows of (a,b), in lexicographic order
+/// let indices = lexsort_to_indices(&sort_columns, None).unwrap();
+/// assert_eq!(&indices, &UInt32Array::from(vec![2, 1, 0]));
+/// // Create new sorted RecordBatch by copying values at indices
+/// let sorted = take_record_batch(&batch, &indices).unwrap();
+///
+/// assert_eq!(sorted.column(0).as_ref(), &Int32Array::from(vec![1, 1, 2]));
+/// assert_eq!(sorted.column(1).as_ref(), &StringArray::from(vec!["a", "z",
"x"]));
+/// ```
+///
/// Note: for multi-column sorts without a limit, using the [row
format](https://docs.rs/arrow-row/latest/arrow_row/)
/// may be significantly faster
pub fn lexsort_to_indices(
