From 8f83a6683086de277b87c92510e052ced065ea79 Mon Sep 17 00:00:00 2001
From: Raphael Taylor-Davies <r.taylordavies@googlemail.com>
Date: Thu, 10 Nov 2022 14:53:24 +1300
Subject: [PATCH 1/2] Deprecate Buffer::count_set_bits (#3067)

---
 arrow-buffer/src/buffer/immutable.rs    | 21 +++++++++++----------
 arrow-select/src/filter.rs              |  2 +-
 arrow/src/compute/kernels/arithmetic.rs |  3 ---
 3 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/arrow-buffer/src/buffer/immutable.rs b/arrow-buffer/src/buffer/immutable.rs
index c60d28afc782..afac76c4dd75 100644
--- a/arrow-buffer/src/buffer/immutable.rs
+++ b/arrow-buffer/src/buffer/immutable.rs
@@ -215,6 +215,7 @@ impl Buffer {
     }
 
     /// Returns the number of 1-bits in this buffer.
+    #[deprecated(note = "use count_set_bits_offset instead")]
     pub fn count_set_bits(&self) -> usize {
         let len_in_bits = self.len() * 8;
         // self.offset is already taken into consideration by the bit_chunks implementation
@@ -466,11 +467,11 @@ mod tests {
 
     #[test]
     fn test_count_bits() {
-        assert_eq!(0, Buffer::from(&[0b00000000]).count_set_bits());
-        assert_eq!(8, Buffer::from(&[0b11111111]).count_set_bits());
-        assert_eq!(3, Buffer::from(&[0b00001101]).count_set_bits());
-        assert_eq!(6, Buffer::from(&[0b01001001, 0b01010010]).count_set_bits());
-        assert_eq!(16, Buffer::from(&[0b11111111, 0b11111111]).count_set_bits());
+        assert_eq!(0, Buffer::from(&[0b00000000]).count_set_bits_offset(0, 8));
+        assert_eq!(8, Buffer::from(&[0b11111111]).count_set_bits_offset(0, 8));
+        assert_eq!(3, Buffer::from(&[0b00001101]).count_set_bits_offset(0, 8));
+        assert_eq!(6, Buffer::from(&[0b01001001, 0b01010010]).count_set_bits_offset(0, 16));
+        assert_eq!(16, Buffer::from(&[0b11111111, 0b11111111]).count_set_bits_offset(0, 16));
     }
 
     #[test]
@@ -479,31 +480,31 @@ mod tests {
             0,
             Buffer::from(&[0b11111111, 0b00000000])
                 .slice(1)
-                .count_set_bits()
+                .count_set_bits_offset(0, 8)
         );
         assert_eq!(
             8,
             Buffer::from(&[0b11111111, 0b11111111])
                 .slice_with_length(1, 1)
-                .count_set_bits()
+                .count_set_bits_offset(0, 8)
         );
         assert_eq!(
             3,
             Buffer::from(&[0b11111111, 0b11111111, 0b00001101])
                 .slice(2)
-                .count_set_bits()
+                .count_set_bits_offset(0, 8)
         );
         assert_eq!(
             6,
             Buffer::from(&[0b11111111, 0b01001001, 0b01010010])
                 .slice_with_length(1, 2)
-                .count_set_bits()
+                .count_set_bits_offset(0, 16)
         );
         assert_eq!(
             16,
             Buffer::from(&[0b11111111, 0b11111111, 0b11111111, 0b11111111])
                 .slice(2)
-                .count_set_bits()
+                .count_set_bits_offset(0, 16)
         );
     }
 
diff --git a/arrow-select/src/filter.rs b/arrow-select/src/filter.rs
index 4596afc8791f..f454397647c3 100644
--- a/arrow-select/src/filter.rs
+++ b/arrow-select/src/filter.rs
@@ -413,7 +413,7 @@ fn filter_null_mask(
     let nulls = filter_bits(data.null_buffer()?, data.offset(), predicate);
     // The filtered `nulls` has a length of `predicate.count` bits and
     // therefore the null count is this minus the number of valid bits
-    let null_count = predicate.count - nulls.count_set_bits();
+    let null_count = predicate.count - nulls.count_set_bits_offset(0, predicate.count);
 
     if null_count == 0 {
         return None;
diff --git a/arrow/src/compute/kernels/arithmetic.rs b/arrow/src/compute/kernels/arithmetic.rs
index b310d4fbf8cd..328ce02e4f5d 100644
--- a/arrow/src/compute/kernels/arithmetic.rs
+++ b/arrow/src/compute/kernels/arithmetic.rs
@@ -3059,9 +3059,6 @@ mod tests {
 
         let null_buffer = null_buffer_builder.finish();
 
-        // `count_set_bits` counts 1-bits in entire buffer. Because above `resize` doesn't
-        // actually truncate the buffer, `count_set_bits` still return 3.
-        assert_eq!(null_buffer.count_set_bits(), 3);
         // `count_set_bits_offset` takes len in bits as parameter.
         assert_eq!(null_buffer.count_set_bits_offset(0, 13), 0);
 

From 25a37cf4ffe11d27dba538267de5d37fbe0d4221 Mon Sep 17 00:00:00 2001
From: Raphael Taylor-Davies <r.taylordavies@googlemail.com>
Date: Thu, 10 Nov 2022 15:10:37 +1300
Subject: [PATCH 2/2] Format

---
 arrow-buffer/src/buffer/immutable.rs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arrow-buffer/src/buffer/immutable.rs b/arrow-buffer/src/buffer/immutable.rs
index afac76c4dd75..94bc98678a61 100644
--- a/arrow-buffer/src/buffer/immutable.rs
+++ b/arrow-buffer/src/buffer/immutable.rs
@@ -470,8 +470,14 @@ mod tests {
         assert_eq!(0, Buffer::from(&[0b00000000]).count_set_bits_offset(0, 8));
         assert_eq!(8, Buffer::from(&[0b11111111]).count_set_bits_offset(0, 8));
         assert_eq!(3, Buffer::from(&[0b00001101]).count_set_bits_offset(0, 8));
-        assert_eq!(6, Buffer::from(&[0b01001001, 0b01010010]).count_set_bits_offset(0, 16));
-        assert_eq!(16, Buffer::from(&[0b11111111, 0b11111111]).count_set_bits_offset(0, 16));
+        assert_eq!(
+            6,
+            Buffer::from(&[0b01001001, 0b01010010]).count_set_bits_offset(0, 16)
+        );
+        assert_eq!(
+            16,
+            Buffer::from(&[0b11111111, 0b11111111]).count_set_bits_offset(0, 16)
+        );
     }
 
     #[test]