(arrow-rs) branch main updated: Minor: document why FixedSizeBinary offset is always 0 (#9861)

[alamb]

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The following commit(s) were added to refs/heads/main by this push:
     new 7ad2299e8c Minor: document why FixedSizeBinary offset is always 0 
(#9861)
7ad2299e8c is described below

commit 7ad2299e8cc1be2af4648fa7df412c3338fa3b3c
Author: Andrew Lamb <and...@nerdnetworks.org>
AuthorDate: Fri May 1 08:18:19 2026 -0400

    Minor: document why FixedSizeBinary offset is always 0 (#9861)
    
    # Which issue does this PR close?
    
    - related to https://github.com/apache/arrow-rs/pull/9850
    
    # Rationale for this change
    
    While working on https://github.com/apache/arrow-rs/pull/9850 I noticed
    that FixedSizeBinaryArray::offset always returns zero.
    
    This was confusing to me and so I wanted to document it for future
    readrs
    
    # What changes are included in this PR?
    
    Add some comments
    
    # Are these changes tested?
    
    By CI
    
    # Are there any user-facing changes?
    No, this is internal comments
---
 arrow-array/src/array/fixed_size_binary_array.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arrow-array/src/array/fixed_size_binary_array.rs 
b/arrow-array/src/array/fixed_size_binary_array.rs
index e8272be5d6..39bfc1db4a 100644
--- a/arrow-array/src/array/fixed_size_binary_array.rs
+++ b/arrow-array/src/array/fixed_size_binary_array.rs
@@ -643,6 +643,8 @@ unsafe impl Array for FixedSizeBinaryArray {
     }
 
     fn offset(&self) -> usize {
+        // Slices are normalized by slicing `value_data`/`nulls` directly;
+        // FSB does not retain a separate logical element offset.
         0
     }