Function read_mask_batch 

fn read_mask_batch(
    array_reader: &mut dyn ArrayReader,
    mask_cursor: &mut MaskCursor,
    batch_size: usize,
) -> Result<Option<RecordBatch>>

Reads one logical Mask batch, potentially spanning multiple loaded ranges.

Each MaskCursor chunk is safe to decode because it stays within loaded pages. Gaps are crossed with [ArrayReader::skip_records], while decoded arrays and their mask fragments remain buffered. Once batch_size selected rows have accumulated, this consumes the underlying batch and filters it once with the combined mask.