(arrow-rs) branch main updated: perf(parquet): trim bitmap-backed row selections using 64-bit words (#11639)

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github-merge-queue[bot] 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 781baa4279 perf(parquet): trim bitmap-backed row selections using 64-bit words (#11639)
781baa4279 is described below

commit 781baa42796c5b25c98fa8f0fc7379c16c782df2
Author: Huaijin <ha...@gmail.com>
AuthorDate: Sat Oct 17 08:48:38 2026 +0000

    perf(parquet): trim bitmap-backed row selections using 64-bit words (#11639)
    
    # Which issue does this PR close?
    
    Closes #11640
    
    # Rationale for this change
    
    Trimming a bitmap-backed row selection scans trailing unset bits byte by
    byte. Long tails of skipped rows add unnecessary selection setup
    overhead.
    
    # What changes are included in this PR?
    
    Scan backwards through 64-bit words using `BitChunks`, checking the
    masked remainder first. Use `leading_zeros` to locate the final selected
    row.
    
    This reuses existing handling of bit offsets and padding while
    preserving the fast path for selections that need no trimming.
    
    The implementation was prepared with AI assistance.
    
    # Are these changes tested?
    
    Validated with the existing randomized trim equivalence tests and cursor
    tests covering word boundaries, long zero tails, non-zero bit offsets,
    and set bits outside the logical slice. All 89 selection tests pass.
    
    # Are there any significant user-facing changes?
    
    No.
---
 .../src/arrow/arrow_reader/selection/boolean.rs    | 25 +++++++++-------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/parquet/src/arrow/arrow_reader/selection/boolean.rs b/parquet/src/arrow/arrow_reader/selection/boolean.rs
index e5b698533a..ca21ffe0f4 100644
--- a/parquet/src/arrow/arrow_reader/selection/boolean.rs
+++ b/parquet/src/arrow/arrow_reader/selection/boolean.rs
@@ -250,22 +250,17 @@ pub(super) fn split_off_mask(
     (head, tail)
 }
 
-/// Position of the highest set bit in `mask`, scanning bytes from the end.
+/// Position of the highest set bit in `mask`, scanning words from the end.
 fn last_set_bit_position(mask: &BooleanBuffer) -> Option<usize> {
-    let values = mask.values();
-    let offset = mask.offset();
-    let end = offset + mask.len();
-    for byte_idx in (offset / 8..end.div_ceil(8)).rev() {
-        let byte_start = byte_idx * 8;
-        let mut byte = values[byte_idx];
-        if end - byte_start < 8 {
-            byte &= (1u8 << (end - byte_start)) - 1;
-        }
-        if byte_start < offset {
-            byte &= !((1u8 << (offset - byte_start)) - 1);
-        }
-        if byte != 0 {
-            return Some(byte_start + 7 - byte.leading_zeros() as usize - offset);
+    let chunks = mask.bit_chunks();
+    let remainder = chunks.remainder_bits();
+    if remainder != 0 {
+        return Some(chunks.chunk_len() * 64 + 63 - remainder.leading_zeros() as usize);
+    }
+    for i in (0..chunks.chunk_len()).rev() {
+        let word = chunks.chunk(i);
+        if word != 0 {
+            return Some(i * 64 + 63 - word.leading_zeros() as usize);
         }
     }
     None