Function scatter

datafusion/physical-expr-common/src/utils.rs:76–102

Scatter `truthy` array by boolean mask. When the mask evaluates `true`, next values of `truthy` are taken, when the mask evaluates `false` values null values are filled. # Arguments `mask` - Boolean values used to determine where to put the `truthy` values `truthy` - All values of this array are to scatter according to `mask` into final result.

(mask: &BooleanArray, truthy: &dyn Array)

/// * `mask` - Boolean values used to determine where to put the `truthy` values
/// * `truthy` - All values of this array are to scatter according to `mask` into final result.
pub fn scatter(mask: &BooleanArray, truthy: &dyn Array) -> Result<ArrayRef> {
    let mask = match mask.null_count() {
        0 => Cow::Borrowed(mask),
        n if n == mask.len() => {
            return Ok(new_null_array(truthy.data_type(), mask.len()));
        }
        _ => Cow::Owned(prep_null_mask_filter(mask)),
    };

    let output_len = mask.len();

    // Fast path: no true values mean all-null object
    if !mask.has_true() {
        return Ok(new_null_array(truthy.data_type(), output_len));
    }

    // Fast path: all true means output = truthy
    if mask.null_count() == 0 && !mask.has_false() {
        return Ok(truthy.slice(0, truthy.len()));
    }

    let count = mask.true_count();
    let selectivity = count as f64 / output_len as f64;
    let mask_buffer = mask.values();

    scatter_array(truthy, mask_buffer, output_len, selectivity)
}

fn scatter_array(
    truthy: &dyn Array,