(arrow-rs) branch main updated: Fix `MutableBuffer::clear` (#9622)

[alamb]

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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 1a169cd638 Fix `MutableBuffer::clear` (#9622)
1a169cd638 is described below

commit 1a169cd638aa4b72ccb4961e37e5014a66308718
Author: Alexander Rafferty <he...@alexanderrafferty.com>
AuthorDate: Wed Apr 1 06:27:16 2026 +1100

    Fix `MutableBuffer::clear` (#9622)
    
    # Which issue does this PR close?
    
    - closes https://github.com/apache/arrow-rs/pull/9593
    
    # Rationale for this change
    
    In a previous PR (#9593), I change instances of `truncate(0)` to
    `clear()`. However, this breaks the test `test_truncate_with_pool` at
    `arrow-buffer/src/buffer/mutable.rs:1357`, due to an inconsistency
    between the implementation of `truncate` and `clear`. This PR fixes that
    test.
    
    # What changes are included in this PR?
    
    This PR copies a section of code related to the `pool` feature present
    in `truncate` but absent in `clear`, fixing the failing unit test.
    
    # Are these changes tested?
    
    Yes.
    
    # Are there any user-facing changes?
    
    No.
---
 arrow-buffer/src/buffer/mutable.rs  | 10 ++++++++--
 arrow-json/src/reader/value_iter.rs |  2 +-
 parquet/tests/geospatial.rs         |  4 ++--
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arrow-buffer/src/buffer/mutable.rs 
b/arrow-buffer/src/buffer/mutable.rs
index 9fc8605061..07ef965cb0 100644
--- a/arrow-buffer/src/buffer/mutable.rs
+++ b/arrow-buffer/src/buffer/mutable.rs
@@ -450,7 +450,13 @@ impl MutableBuffer {
 
     /// Clear all existing data from this buffer.
     pub fn clear(&mut self) {
-        self.len = 0
+        self.len = 0;
+        #[cfg(feature = "pool")]
+        {
+            if let Some(reservation) = 
self.reservation.lock().unwrap().as_mut() {
+                reservation.resize(self.len);
+            }
+        }
     }
 
     /// Returns the data stored in this buffer as a slice.
@@ -1371,7 +1377,7 @@ mod tests {
             assert_eq!(pool.used(), 40);
 
             // Truncate to zero
-            buffer.truncate(0);
+            buffer.clear();
             assert_eq!(buffer.len(), 0);
             assert_eq!(pool.used(), 0);
         }
diff --git a/arrow-json/src/reader/value_iter.rs 
b/arrow-json/src/reader/value_iter.rs
index f70b893f52..ebaba695ad 100644
--- a/arrow-json/src/reader/value_iter.rs
+++ b/arrow-json/src/reader/value_iter.rs
@@ -73,7 +73,7 @@ impl<R: BufRead> Iterator for ValueIter<R> {
         }
 
         loop {
-            self.line_buf.truncate(0);
+            self.line_buf.clear();
             match self.reader.read_line(&mut self.line_buf) {
                 Ok(0) => {
                     // read_line returns 0 when stream reached EOF
diff --git a/parquet/tests/geospatial.rs b/parquet/tests/geospatial.rs
index 4f449df920..fcc93661ed 100644
--- a/parquet/tests/geospatial.rs
+++ b/parquet/tests/geospatial.rs
@@ -380,8 +380,8 @@ mod test {
 
         for i in 0..reader.num_row_groups() {
             let row_group = reader.get_row_group(i).unwrap();
-            values.truncate(0);
-            def_levels.truncate(0);
+            values.clear();
+            def_levels.clear();
 
             let mut row_group_out = writer.next_row_group().unwrap();