Function nullif

arrow-select/src/nullif.rs:44–112

Returns a new array with the same values and the validity bit to false where the corresponding element of `right` is true. This can be used to implement SQL `NULLIF` # Example ``` # use arrow_array::{Int32Array, BooleanArray}; # use arrow_array::cast::AsArray; # use arrow_array::types::Int32Type; # use arrow_select::nullif::nullif; // input is [null, 8, 1, 9] let a = Int32Array::from(vec![None,

(left: &dyn Array, right: &BooleanArray)

/// assert_eq!(nulled.as_primitive(), &Int32Array::from(vec![None, None, Some(1), Some(9)]));
/// ```
pub fn nullif(left: &dyn Array, right: &BooleanArray) -> Result<ArrayRef, ArrowError> {
    let left_data = left.to_data();

    if left_data.len() != right.len() {
        return Err(ArrowError::ComputeError(
            "Cannot perform comparison operation on arrays of different length".to_string(),
        ));
    }
    let len = left_data.len();

    if len == 0 || left_data.data_type() == &DataType::Null {
        return Ok(make_array(left_data));
    }

    // left=0 (null)   right=null       output bitmap=null
    // left=0          right=1          output bitmap=null
    // left=1 (set)    right=null       output bitmap=set   (passthrough)
    // left=1          right=1 & comp=true    output bitmap=null
    // left=1          right=1 & comp=false   output bitmap=set
    //
    // Thus: result = left null bitmap & (!right_values | !right_bitmap)
    //              OR left null bitmap & !(right_values & right_bitmap)

    // Compute right_values & right_bitmap
    let right = match right.nulls() {
        Some(nulls) => right.values() & nulls.inner(),
        None => right.values().clone(),
    };

    // Compute left null bitmap & !right

    let (combined, null_count) = match left_data.nulls() {
        Some(left) => {
            let mut valid_count = 0;
            let b = bitwise_bin_op_helper(
                left.buffer(),
                left.offset(),
                right.inner(),
                right.offset(),
                len,
                |l, r| {
                    let t = l & !r;
                    valid_count += t.count_ones() as usize;
                    t
                },
            );
            (b, len - valid_count)
        }
        None => {
            let mut null_count = 0;
            let buffer = bitwise_unary_op_helper(right.inner(), right.offset(), len, |b| {
                let t = !b;
                null_count += t.count_zeros() as usize;
                t
            });
            (buffer, null_count)
        }
    };