Function compact_lane_input 

fn compact_lane_input(
    timestamps: &TimestampMillisecondArray,
    values: &dyn Array,
    valid: &[bool],
    prefix: &[usize],
    bounds: &[(usize, usize)],
    selections: &[Option<SampleLane>],
    lane: SampleLane,
    name: &str,
) -> Result<Vec<ColumnarValue>>

Filters null placeholders from one sample lane and remaps its selected windows. Windows assigned to the other lane become empty.