refactor: Use Signature::coercible for isnan/iszero (#19604)

## Which issue does this PR close?

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- Part of #14763.

## Rationale for this change

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in the issue then this section is not needed.
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## What changes are included in this PR?

Replace `TypeSignature::Exact` patterns with cleaner APIs:
- `isnan/iszero`: `Signature::coercible` with
`TypeSignatureClass::Float`
- `nanvl`: `Signature::uniform(2, [Float32, Float64])`

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## Are these changes tested?

Yes

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---------

Co-authored-by: Jeffrey Vo <[email protected]>

Author: kumarUjjawal

datafusion/functions/src/math/iszero.rs

@@ -18,12 +18,13 @@
 use std::any::Any;
 use std::sync::Arc;
 
-use arrow::array::{ArrayRef, AsArray, BooleanArray};
-use arrow::datatypes::DataType::{Boolean, Float32, Float64};
-use arrow::datatypes::{DataType, Float32Type, Float64Type};
+use arrow::array::{ArrayRef, ArrowNativeTypeOp, AsArray, BooleanArray};
+use arrow::datatypes::DataType::{Boolean, Float16, Float32, Float64};
+use arrow::datatypes::{DataType, Float16Type, Float32Type, Float64Type};
 
-use datafusion_common::{Result, exec_err};
-use datafusion_expr::TypeSignature::Exact;
+use datafusion_common::types::NativeType;
+use datafusion_common::{Result, ScalarValue, exec_err};
+use datafusion_expr::{Coercion, TypeSignatureClass};
 use datafusion_expr::{
     ColumnarValue, Documentation, ScalarFunctionArgs, ScalarUDFImpl, Signature,
     Volatility,
@@ -59,12 +60,14 @@ impl Default for IsZeroFunc {
 
 impl IsZeroFunc {
     pub fn new() -> Self {
-        use DataType::*;
+        // Accept any numeric type and coerce to float
+        let float = Coercion::new_implicit(
+            TypeSignatureClass::Float,
+            vec![TypeSignatureClass::Numeric],
+            NativeType::Float64,
+        );
         Self {
-            signature: Signature::one_of(
-                vec![Exact(vec![Float32]), Exact(vec![Float64])],
-                Volatility::Immutable,
-            ),
+            signature: Signature::coercible(vec![float], Volatility::Immutable),
         }
     }
 }
@@ -87,6 +90,10 @@ impl ScalarUDFImpl for IsZeroFunc {
     }
 
     fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
+        // Handle NULL input
+        if args.args[0].data_type().is_null() {
+            return Ok(ColumnarValue::Scalar(ScalarValue::Boolean(None)));
+        }
         make_scalar_function(iszero, vec![])(&args.args)
     }
 
@@ -108,6 +115,11 @@ fn iszero(args: &[ArrayRef]) -> Result<ArrayRef> {
             |x| x == 0.0,
         )) as ArrayRef),
 
+        Float16 => Ok(Arc::new(BooleanArray::from_unary(
+            args[0].as_primitive::<Float16Type>(),
+            |x| x.is_zero(),
+        )) as ArrayRef),
+
         other => exec_err!("Unsupported data type {other:?} for function iszero"),
     }
 }

datafusion/functions/src/math/nans.rs

@@ -17,9 +17,10 @@
 
 //! Math function: `isnan()`.
 
-use arrow::datatypes::{DataType, Float32Type, Float64Type};
-use datafusion_common::{Result, exec_err};
-use datafusion_expr::{ColumnarValue, ScalarFunctionArgs, TypeSignature};
+use arrow::datatypes::{DataType, Float16Type, Float32Type, Float64Type};
+use datafusion_common::types::NativeType;
+use datafusion_common::{Result, ScalarValue, exec_err};
+use datafusion_expr::{Coercion, ColumnarValue, ScalarFunctionArgs, TypeSignatureClass};
 
 use arrow::array::{ArrayRef, AsArray, BooleanArray};
 use datafusion_expr::{Documentation, ScalarUDFImpl, Signature, Volatility};
@@ -54,15 +55,14 @@ impl Default for IsNanFunc {
 
 impl IsNanFunc {
     pub fn new() -> Self {
-        use DataType::*;
+        // Accept any numeric type and coerce to float
+        let float = Coercion::new_implicit(
+            TypeSignatureClass::Float,
+            vec![TypeSignatureClass::Numeric],
+            NativeType::Float64,
+        );
         Self {
-            signature: Signature::one_of(
-                vec![
-                    TypeSignature::Exact(vec![Float32]),
-                    TypeSignature::Exact(vec![Float64]),
-                ],
-                Volatility::Immutable,
-            ),
+            signature: Signature::coercible(vec![float], Volatility::Immutable),
         }
     }
 }
@@ -84,6 +84,11 @@ impl ScalarUDFImpl for IsNanFunc {
     }
 
     fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
+        // Handle NULL input
+        if args.args[0].data_type().is_null() {
+            return Ok(ColumnarValue::Scalar(ScalarValue::Boolean(None)));
+        }
+
         let args = ColumnarValue::values_to_arrays(&args.args)?;
 
         let arr: ArrayRef = match args[0].data_type() {
@@ -96,6 +101,11 @@ impl ScalarUDFImpl for IsNanFunc {
                 args[0].as_primitive::<Float32Type>(),
                 f32::is_nan,
             )) as ArrayRef,
+
+            DataType::Float16 => Arc::new(BooleanArray::from_unary(
+                args[0].as_primitive::<Float16Type>(),
+                |x| x.is_nan(),
+            )) as ArrayRef,
             other => {
                 return exec_err!(
                     "Unsupported data type {other:?} for function {}",

datafusion/functions/src/math/nanvl.rs

@@ -20,9 +20,9 @@ use std::sync::Arc;
 
 use crate::utils::make_scalar_function;
 
-use arrow::array::{ArrayRef, AsArray, Float32Array, Float64Array};
-use arrow::datatypes::DataType::{Float32, Float64};
-use arrow::datatypes::{DataType, Float32Type, Float64Type};
+use arrow::array::{ArrayRef, AsArray, Float16Array, Float32Array, Float64Array};
+use arrow::datatypes::DataType::{Float16, Float32, Float64};
+use arrow::datatypes::{DataType, Float16Type, Float32Type, Float64Type};
 use datafusion_common::{DataFusionError, Result, exec_err};
 use datafusion_expr::TypeSignature::Exact;
 use datafusion_expr::{
@@ -66,10 +66,13 @@ impl Default for NanvlFunc {
 
 impl NanvlFunc {
     pub fn new() -> Self {
-        use DataType::*;
         Self {
             signature: Signature::one_of(
-                vec![Exact(vec![Float32, Float32]), Exact(vec![Float64, Float64])],
+                vec![
+                    Exact(vec![Float16, Float16]),
+                    Exact(vec![Float32, Float32]),
+                    Exact(vec![Float64, Float64]),
+                ],
                 Volatility::Immutable,
             ),
         }
@@ -91,6 +94,7 @@ impl ScalarUDFImpl for NanvlFunc {
 
     fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
         match &arg_types[0] {
+            Float16 => Ok(Float16),
             Float32 => Ok(Float32),
             _ => Ok(Float64),
         }
@@ -130,6 +134,19 @@ fn nanvl(args: &[ArrayRef]) -> Result<ArrayRef> {
                 .map(|res| Arc::new(res) as _)
                 .map_err(DataFusionError::from)
         }
+        Float16 => {
+            let compute_nanvl =
+                |x: <Float16Type as arrow::datatypes::ArrowPrimitiveType>::Native,
+                 y: <Float16Type as arrow::datatypes::ArrowPrimitiveType>::Native| {
+                    if x.is_nan() { y } else { x }
+                };
+
+            let x = args[0].as_primitive() as &Float16Array;
+            let y = args[1].as_primitive() as &Float16Array;
+            arrow::compute::binary::<_, _, _, Float16Type>(x, y, compute_nanvl)
+                .map(|res| Arc::new(res) as _)
+                .map_err(DataFusionError::from)
+        }
         other => exec_err!("Unsupported data type {other:?} for function nanvl"),
     }
 }