Jefffrey commented on code in PR #20205:
URL: https://github.com/apache/datafusion/pull/20205#discussion_r2793930675
##########
datafusion/functions/src/math/nanvl.rs:
##########
@@ -110,42 +125,54 @@ impl ScalarUDFImpl for NanvlFunc {
}
/// Nanvl SQL function
+///
+/// Only propagates nulls from x:
Review Comment:
This is misleading as we can still propagate nulls from y too (as
highlighted by the 2nd point)
##########
datafusion/functions/src/math/nanvl.rs:
##########
@@ -110,42 +125,54 @@ impl ScalarUDFImpl for NanvlFunc {
}
/// Nanvl SQL function
+///
+/// Only propagates nulls from x:
+/// - x is NULL -> output is NULL
+/// - x is NaN -> output is y (even if y is NULL)
+/// - x is not NaN -> output is x (regardless of y)
fn nanvl(args: &[ArrayRef]) -> Result<ArrayRef> {
match args[0].data_type() {
Float64 => {
- let compute_nanvl = |x: f64, y: f64| {
- if x.is_nan() { y } else { x }
- };
-
- let x = args[0].as_primitive() as &Float64Array;
- let y = args[1].as_primitive() as &Float64Array;
- arrow::compute::binary::<_, _, _, Float64Type>(x, y, compute_nanvl)
- .map(|res| Arc::new(res) as _)
- .map_err(DataFusionError::from)
+ let x = args[0].as_primitive::<Float64Type>();
+ let y = args[1].as_primitive::<Float64Type>();
+ let result: Float64Array = x
+ .iter()
+ .zip(y.iter())
+ .map(|(xv, yv)| match xv {
+ None => None, // x is null -> null
+ Some(xv) if xv.is_nan() => yv, // x is NaN -> y
+ some_xv => some_xv, // x is valid -> x
+ })
Review Comment:
```rust
.map(|(x_value, y_value)| match x_value {
Some(x_value) if x_value.is_nan() => y_value,
_ => x_value,
```
Can keep this simple
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