(arrow-rs) branch main updated: feat: add `reserve` to `Rows` (#9142)

[alamb]

This is an automated email from the ASF dual-hosted git repository.

alamb pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/arrow-rs.git


The following commit(s) were added to refs/heads/main by this push:
     new a7b89073bd feat: add `reserve` to `Rows` (#9142)
a7b89073bd is described below

commit a7b89073bd428e5dafde872201ccda97ccd6bbed
Author: Raz Luvaton <16746759+rluva...@users.noreply.github.com>
AuthorDate: Tue Jan 13 14:15:14 2026 +0200

    feat: add `reserve` to `Rows` (#9142)
    
    # Which issue does this PR close?
    
    N/A
    
    # Rationale for this change
    
    allow to reserve so we can avoid reallocating
    
    # What changes are included in this PR?
    
    added `reserve` function to `Rows` + tests
    
    # Are these changes tested?
    
    yes
    
    # Are there any user-facing changes?
    
    yes
---
 arrow-row/src/lib.rs | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/arrow-row/src/lib.rs b/arrow-row/src/lib.rs
index 4cafbc2748..2f6ffd76d9 100644
--- a/arrow-row/src/lib.rs
+++ b/arrow-row/src/lib.rs
@@ -1130,6 +1130,12 @@ impl Rows {
         self.offsets.push(self.buffer.len())
     }
 
+    /// Reserve capacity for `row_capacity` rows with a total length of 
`data_capacity`
+    pub fn reserve(&mut self, row_capacity: usize, data_capacity: usize) {
+        self.buffer.reserve(data_capacity);
+        self.offsets.reserve(row_capacity);
+    }
+
     /// Returns the row at index `row`
     pub fn row(&self, row: usize) -> Row<'_> {
         assert!(row + 1 < self.offsets.len());
@@ -4283,4 +4289,38 @@ mod tests {
             "{empty_rows_size_with_preallocate_data} should be larger than 
{empty_rows_size_without_preallocate}"
         );
     }
+
+    #[test]
+    fn reserve_should_increase_capacity_to_the_requested_size() {
+        let row_converter = 
RowConverter::new(vec![SortField::new(DataType::UInt8)]).unwrap();
+        let mut empty_rows = row_converter.empty_rows(0, 0);
+        empty_rows.reserve(50, 50);
+        let before_size = empty_rows.size();
+        empty_rows.reserve(50, 50);
+        assert_eq!(
+            empty_rows.size(),
+            before_size,
+            "Size should not change when reserving already reserved space"
+        );
+        empty_rows.reserve(10, 20);
+        assert_eq!(
+            empty_rows.size(),
+            before_size,
+            "Size should not change when already have space for the expected 
reserved data"
+        );
+
+        empty_rows.reserve(100, 20);
+        assert!(
+            empty_rows.size() > before_size,
+            "Size should increase when reserving more space than previously 
reserved"
+        );
+
+        let before_size = empty_rows.size();
+
+        empty_rows.reserve(20, 100);
+        assert!(
+            empty_rows.size() > before_size,
+            "Size should increase when reserving more space than previously 
reserved"
+        );
+    }
 }