Method mask_sparse_helper

arrow-array/src/array/union_array.rs:571–605

Maps `nulls` to `BitChunk's` and then to `BitChunkIterator's`, then divides `self.type_ids` into exact chunks of 64 values, calling `mask_chunk` for every exact chunk, and `mask_remainder` for the remainder, if any, collecting the result in a `BooleanBuffer`

(
        &self,
        nulls: Vec<(i8, NullBuffer)>,
        mut mask_chunk: impl FnMut(&[i8; 64], &mut [(i8, BitChunkIterator)]) -> u64,
        mask_remainder: impl FnOnce(&[i8], &[(i8, BitChunks)

    /// Maps `nulls` to `BitChunk's` and then to `BitChunkIterator's`, then divides `self.type_ids` into exact chunks of 64 values,
    /// calling `mask_chunk` for every exact chunk, and `mask_remainder` for the remainder, if any, collecting the result in a `BooleanBuffer`
    fn mask_sparse_helper(
        &self,
        nulls: Vec<(i8, NullBuffer)>,
        mut mask_chunk: impl FnMut(&[i8; 64], &mut [(i8, BitChunkIterator)]) -> u64,
        mask_remainder: impl FnOnce(&[i8], &[(i8, BitChunks)]) -> u64,
    ) -> BooleanBuffer {
        let bit_chunks = nulls
            .iter()
            .map(|(type_id, nulls)| (*type_id, nulls.inner().bit_chunks()))
            .collect::<Vec<_>>();

        let mut nulls_masks_iter = bit_chunks
            .iter()
            .map(|(type_id, bit_chunks)| (*type_id, bit_chunks.iter()))
            .collect::<Vec<_>>();

        let chunks_exact = self.type_ids.chunks_exact(64);
        let remainder = chunks_exact.remainder();

        let chunks = chunks_exact.map(|type_ids_chunk| {
            let type_ids_chunk_array = <&[i8; 64]>::try_from(type_ids_chunk).unwrap();

            mask_chunk(type_ids_chunk_array, &mut nulls_masks_iter)
        });

        // SAFETY:
        // chunks is a ChunksExact iterator, which implements TrustedLen, and correctly reports its length
        let mut buffer = unsafe { MutableBuffer::from_trusted_len_iter(chunks) };

        if !remainder.is_empty() {
            buffer.push(mask_remainder(remainder, &bit_chunks));
        }

        BooleanBuffer::new(buffer.into(), 0, self.type_ids.len())
    }

    /// Computes the logical nulls for a sparse or dense union, by gathering individual bits from the null buffer of the selected field
    fn gather_nulls(&self, nulls: Vec<(i8, NullBuffer)>) -> BooleanBuffer {