tustvold commented on a change in pull request #1248:
URL: https://github.com/apache/arrow-rs/pull/1248#discussion_r795106504
##########
File path: arrow/src/compute/kernels/filter.rs
##########
@@ -244,6 +419,110 @@ pub fn filter_record_batch(
RecordBatch::try_new(record_batch.schema(), filtered_arrays)
}
+fn filter_null_mask(
+ data: &ArrayData,
+ filter: &BooleanArray,
+ filter_count: usize,
+) -> Option<(usize, Buffer)> {
+ if data.null_count() == 0 {
+ return None;
+ }
+
+ let nulls = filter_bits(data.null_buffer()?, data.offset(), filter,
filter_count);
+ let null_count = filter_count - nulls.count_set_bits();
+
+ if null_count == 0 {
+ return None;
+ }
+
+ Some((null_count, nulls))
+}
+
+fn filter_bits(
+ buffer: &Buffer,
+ offset: usize,
+ filter: &BooleanArray,
+ filter_count: usize,
+) -> Buffer {
+ let src = buffer.as_slice();
+
+ // TODO: Optimise this
+ let mut buf = MutableBuffer::from_len_zeroed(bit_util::ceil(filter_count,
8));
+ let dst = buf.as_slice_mut();
+
+ for (dst_idx, src_idx) in IndexIterator::new(filter).enumerate() {
+ if bit_util::get_bit(src, src_idx + offset) {
+ bit_util::set_bit(dst, dst_idx);
+ }
+ }
+
+ buf.into()
+}
+
+/// `filter` implementation for boolean buffers
+fn filter_boolean(
+ values: &BooleanArray,
+ filter: &BooleanArray,
+ filter_count: usize,
+) -> BooleanArray {
+ let data = values.data();
+ assert_eq!(data.buffers().len(), 1);
+ assert_eq!(data.child_data().len(), 0);
+
+ let values = filter_bits(&data.buffers()[0], data.offset(), filter,
filter_count);
+
+ let mut builder = ArrayDataBuilder::new(DataType::Boolean)
+ .len(filter_count)
+ .add_buffer(values);
+
+ if let Some((null_count, nulls)) = filter_null_mask(data, filter,
filter_count) {
+ builder = builder.null_count(null_count).null_bit_buffer(nulls);
+ }
+
+ let data = builder.build().unwrap(); // TODO: unsafe {
builder.build_unchecked() };
+ BooleanArray::from(data)
+}
+
+/// `filter` implementation for primitive arrays
+fn filter_primitive<T>(
+ values: &PrimitiveArray<T>,
+ filter: &BooleanArray,
+ filter_count: usize,
+) -> PrimitiveArray<T>
+where
+ T: ArrowPrimitiveType,
+{
+ let data = values.data();
+ assert_eq!(data.buffers().len(), 1);
+ assert_eq!(data.child_data().len(), 0);
+
+ let values = data.buffer::<T::Native>(0);
+
+ let mut buffer = MutableBuffer::with_capacity(filter_count *
T::get_byte_width());
+
+ let selectivity_frac = filter_count as f64 / filter.len() as f64;
Review comment:
Credit to @sunchao for the inspiration behind this hybrid approach -
https://github.com/apache/arrow-rs/issues/1191#issuecomment-1023658537
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