alamb commented on code in PR #1499:
URL: https://github.com/apache/arrow-rs/pull/1499#discussion_r848538708
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arrow/src/compute/kernels/boolean.rs:
##########
@@ -575,10 +577,242 @@ where
Ok(PrimitiveArray::<T>::from(data))
}
+/// Creates a (mostly) zero-copy slice of the given buffers so that they can
be combined
+/// in the same array with other buffers that start at offset 0.
+/// The only buffers that need an actual copy are booleans (if they are not
byte-aligned)
+/// and list/binary/string offsets because the arrow implementation requires
them to start at 0.
+/// This is useful when a kernel calculates a new validity bitmap but wants to
reuse other buffers.
+fn slice_buffers(
+ buffers: &[Buffer],
+ offset: usize,
+ len: usize,
+ data_type: &DataType,
+ child_data: &[ArrayData],
+) -> (Vec<Buffer>, Vec<ArrayData>) {
+ use std::mem::size_of;
+
+ if offset == 0 {
+ return (buffers.to_vec(), child_data.to_vec());
+ }
+
+ // we only need to do something special to child data in 2 of the match
branches
+ let mut result_child_data = None;
+
+ let result_buffers = match data_type {
+ DataType::Boolean => vec![buffers[0].bit_slice(offset, len)],
+ DataType::Int8 | DataType::UInt8 => {
+ vec![buffers[0].slice(offset * size_of::<u8>())]
+ }
+ DataType::Int16 | DataType::UInt16 | DataType::Float16 => {
+ vec![buffers[0].slice(offset * size_of::<u16>())]
+ }
+ DataType::Int32 | DataType::UInt32 | DataType::Float32 => {
+ vec![buffers[0].slice(offset * size_of::<u32>())]
+ }
+ DataType::Int64 | DataType::UInt64 | DataType::Float64 => {
+ vec![buffers[0].slice(offset * size_of::<u64>())]
+ }
+ DataType::Timestamp(_, _) | DataType::Duration(_) => {
+ vec![buffers[0].slice(offset * size_of::<u64>())]
+ }
+ DataType::Date32 | DataType::Time32(_) => {
+ vec![buffers[0].slice(offset * size_of::<u32>())]
+ }
+ DataType::Date64 | DataType::Time64(_) => {
+ vec![buffers[0].slice(offset * size_of::<u64>())]
+ }
+ DataType::Interval(IntervalUnit::YearMonth) => {
+ vec![buffers[0].slice(offset * size_of::<u32>())]
+ }
+ DataType::Interval(IntervalUnit::DayTime) => {
+ vec![buffers[0].slice(offset * 2 * size_of::<u32>())]
+ }
+ DataType::Interval(IntervalUnit::MonthDayNano) => {
+ vec![buffers[0].slice(offset * (2 * size_of::<u32>() +
size_of::<u64>()))]
+ }
+ DataType::Decimal(_, _) => vec![buffers[0].slice(offset *
size_of::<i128>())],
+ DataType::Dictionary(key_type, _) => match key_type.as_ref() {
+ DataType::Int8 | DataType::UInt8 => {
+ vec![buffers[0].slice(offset * size_of::<u8>())]
+ }
+ DataType::Int16 | DataType::UInt16 => {
+ vec![buffers[0].slice(offset * size_of::<u16>())]
+ }
+ DataType::Int32 | DataType::UInt32 => {
+ vec![buffers[0].slice(offset * size_of::<u32>())]
+ }
+ DataType::Int64 | DataType::UInt64 => {
+ vec![buffers[0].slice(offset * size_of::<u64>())]
+ }
+ _ => unreachable!(),
+ },
+ DataType::List(_) => {
+ // safe because for List the first buffer is guaranteed to contain
i32 offsets
+ let offsets = unsafe { &buffers[0].typed_data()[offset..] };
+ let first_offset = offsets[0] as usize;
+ let last_offset = offsets[len] as usize;
+ let nested_len = last_offset - first_offset;
+
+ // since we calculate a new offset buffer starting from 0 we also
have to slice the child data
+ result_child_data = Some(
+ child_data
+ .iter()
+ .map(|d| d.slice(first_offset, nested_len))
+ .collect(),
+ );
+ vec![offset_buffer_slice::<i32>(offsets, len)]
+ }
+ DataType::LargeList(_) => {
+ // safe because for LargeList the first buffer is guaranteed to
contain i64 offsets
+ let offsets = unsafe { &buffers[0].typed_data()[offset..] };
+ let first_offset = offsets[0] as usize;
+ let last_offset = offsets[len] as usize;
+ let nested_len = last_offset - first_offset;
+ // since we calculate a new offset buffer starting from 0 we also
have to slice the child data
+
+ result_child_data = Some(
+ child_data
+ .iter()
+ .map(|d| d.slice(first_offset, nested_len))
+ .collect(),
+ );
+ vec![offset_buffer_slice::<i64>(offsets, len)]
+ }
+ DataType::Binary | DataType::Utf8 => {
+ // safe because for Binary/Utf8 the first buffer is guaranteed to
contain i32 offsets
+ let offsets = unsafe { &buffers[0].typed_data()[offset..] };
+ let first_offset = offsets[0] as usize;
+ vec![
+ offset_buffer_slice::<i32>(offsets, len),
+ buffers[1].slice(first_offset * size_of::<i32>()),
+ ]
+ }
+ DataType::LargeBinary | DataType::LargeUtf8 => {
+ // safe because for LargeBinary/LargeUtf8 the first buffer is
guaranteed to contain i64 offsets
+ let offsets = unsafe { &buffers[0].typed_data()[offset..] };
+ let first_offset = offsets[0] as usize;
+ vec![
+ offset_buffer_slice::<i64>(offsets, len),
+ buffers[1].slice(first_offset * size_of::<i64>()),
+ ]
+ }
+ DataType::FixedSizeBinary(size) => {
+ vec![buffers[0].slice(offset * (*size as usize))]
+ }
+ DataType::FixedSizeList(_, _size) => {
+ // TODO: should this actually slice the child arrays?
+ vec![]
+ }
+ DataType::Struct(_) => {
+ // TODO: should this actually slice the child arrays?
+ vec![]
+ }
+ DataType::Union(..) => {
+ // TODO: verify this is actually correct
+ if buffers.len() > 1 {
+ // dense union, type ids and offsets
+ vec![
+ buffers[0].slice(offset * size_of::<i8>()),
+ buffers[1].slice(offset * size_of::<u32>()),
+ ]
+ } else {
+ // sparse union with only type ids
+ // should this also slice the child arrays?
+ vec![buffers[0].slice(offset * size_of::<i8>())]
+ }
+ }
+ DataType::Map(_, _) => {
+ // TODO: verify this is actually correct
+ result_child_data =
+ Some(child_data.iter().map(|d| d.slice(offset,
len)).collect());
+ vec![]
+ }
+ DataType::Null => vec![],
+ };
+
+ (
+ result_buffers,
+ result_child_data.unwrap_or_else(|| child_data.to_vec()),
+ )
+}
+
+// ListArray::from(ArrayData) expected offsets to always start at 0 so we
can't simply make a slice of the buffer,
+// but instead have to calculate a new buffer
+fn offset_buffer_slice<T: OffsetSizeTrait>(
+ original_offsets: &[T],
+ array_len: usize,
+) -> Buffer {
+ // offset buffer has 1 element more than the corresponding data buffer
pointing yet another offset for the end of the buffer
+ let len_in_bytes = (array_len + 1) * std::mem::size_of::<T>();
+ let mut offset_buffer =
+ MutableBuffer::new(len_in_bytes).with_bitset(len_in_bytes, false);
+ let offset_slice = unsafe { offset_buffer.typed_data_mut::<T>() };
+ let offset_start = original_offsets[0];
+ offset_slice
+ .iter_mut()
+ .zip(original_offsets.iter())
+ .for_each(|(output, input)| {
+ *output = *input - offset_start;
+ });
+
+ offset_buffer.into()
+}
+
+pub fn nullif_alternative(
+ array: &ArrayRef,
+ condition: &BooleanArray,
+) -> Result<ArrayRef> {
+ if array.len() != condition.len() {
+ return Err(ArrowError::ComputeError(
+ "Inputs to conditional kernels must have the same
length".to_string(),
+ ));
+ }
+
+ let condition_buffer = combine_option_buffers(
+ condition.data().buffers().first(),
+ condition.offset(),
+ condition.data().null_buffer(),
+ condition.offset(),
+ condition.len(),
+ )
+ .map(|b| !&b);
+
+ let result_valid_buffer = combine_option_buffers(
+ condition_buffer.as_ref(),
+ 0,
+ array.data().null_buffer(),
+ array.offset(),
+ condition.len(),
+ );
+
+ let (result_data_buffers, result_child_data) = slice_buffers(
Review Comment:
Perhaps `slice()` belongs on `ArrayData` (which has both the buffers and
datatypes)
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