mapleFU commented on code in PR #6155:
URL: https://github.com/apache/arrow-rs/pull/6155#discussion_r1711413093
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arrow-buffer/src/buffer/null.rs:
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@@ -131,9 +176,20 @@ impl NullBuffer {
}
/// Returns the null count for this [`NullBuffer`]
- #[inline]
pub fn null_count(&self) -> usize {
- self.null_count
+ match &self.null_count {
+ NullCount::Eager(v) => *v,
+ NullCount::Lazy(v) => {
+ let cached_null_count = v.load(Ordering::Acquire);
+ if cached_null_count != UNINITIALIZED_NULL_COUNT {
+ return cached_null_count as usize;
+ }
+
+ let computed_null_count = self.buffer.len() -
self.buffer.count_set_bits();
+ v.store(computed_null_count as i64, Ordering::Release);
Review Comment:
atomic is just a load and store instr? but `count_set_bits()` maybe not
suitable for inline( or it's just __builtin counting zeros)?
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