Function extract_list_values

datafusion/functions-nested/src/lambda_utils.rs:104–126

Extracts flat list values, handling all fast-path short-circuits. - All-null input → `EarlyReturn(null scalar)` - All sublists empty and non-null → `EarlyReturn(default empty-list scalar)` - Otherwise → `Values(flat_values)`

(
    list_array: &ArrayRef,
    return_type: &DataType,
)

/// - All sublists empty and non-null → `EarlyReturn(default empty-list scalar)`
/// - Otherwise → `Values(flat_values)`
pub(crate) fn extract_list_values(
    list_array: &ArrayRef,
    return_type: &DataType,
) -> Result<ListValuesResult> {
    if list_array.null_count() == list_array.len() {
        return Ok(ListValuesResult::EarlyReturn(ColumnarValue::Scalar(
            ScalarValue::try_new_null(return_type)?,
        )));
    }

    let values = list_values(list_array)?;

    if values.is_empty()
        && list_array.null_count() == 0
        && matches!(return_type, DataType::List(_) | DataType::LargeList(_))
    {
        return Ok(ListValuesResult::EarlyReturn(ColumnarValue::Scalar(
            ScalarValue::new_default(return_type)?,
        )));
    }

    Ok(ListValuesResult::Values(values))
}

#[cfg(test)]
pub(crate) mod test_utils {