Fix : signum function bug when 0.0 input (#11580)

* add signum unit test

* fix: signum function implementation - input zero output zero

* fix: run cargo fmt

* fix: not specified return type is float64

* fix: sqllogictest

Author: getChan

datafusion/functions/src/math/mod.rs

@@ -35,6 +35,7 @@ pub mod pi;
 pub mod power;
 pub mod random;
 pub mod round;
+pub mod signum;
 pub mod trunc;
 
 // Create UDFs
@@ -81,7 +82,7 @@ make_math_unary_udf!(
 );
 make_udf_function!(random::RandomFunc, RANDOM, random);
 make_udf_function!(round::RoundFunc, ROUND, round);
-make_math_unary_udf!(SignumFunc, SIGNUM, signum, signum, super::signum_order);
+make_udf_function!(signum::SignumFunc, SIGNUM, signum);
 make_math_unary_udf!(SinFunc, SIN, sin, sin, super::sin_order);
 make_math_unary_udf!(SinhFunc, SINH, sinh, sinh, super::sinh_order);
 make_math_unary_udf!(SqrtFunc, SQRT, sqrt, sqrt, super::sqrt_order);

datafusion/functions/src/math/monotonicity.rs

@@ -197,11 +197,6 @@ pub fn radians_order(input: &[ExprProperties]) -> Result<SortProperties> {
     Ok(input[0].sort_properties)
 }
 
-/// Non-decreasing for all real numbers x.
-pub fn signum_order(input: &[ExprProperties]) -> Result<SortProperties> {
-    Ok(input[0].sort_properties)
-}
-
 /// Non-decreasing on \[0, π\] and then non-increasing on \[π, 2π\].
 /// This pattern repeats periodically with a period of 2π.
 // TODO: Implement ordering rule of the SIN function.

datafusion/functions/src/math/signum.rs

@@ -0,0 +1,215 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use std::any::Any;
+use std::sync::Arc;
+
+use arrow::array::{ArrayRef, Float32Array, Float64Array};
+use arrow::datatypes::DataType;
+use arrow::datatypes::DataType::{Float32, Float64};
+
+use datafusion_common::{exec_err, DataFusionError, Result};
+use datafusion_expr::sort_properties::{ExprProperties, SortProperties};
+use datafusion_expr::ColumnarValue;
+use datafusion_expr::{ScalarUDFImpl, Signature, Volatility};
+
+use crate::utils::make_scalar_function;
+
+#[derive(Debug)]
+pub struct SignumFunc {
+    signature: Signature,
+}
+
+impl Default for SignumFunc {
+    fn default() -> Self {
+        SignumFunc::new()
+    }
+}
+
+impl SignumFunc {
+    pub fn new() -> Self {
+        use DataType::*;
+        Self {
+            signature: Signature::uniform(
+                1,
+                vec![Float64, Float32],
+                Volatility::Immutable,
+            ),
+        }
+    }
+}
+
+impl ScalarUDFImpl for SignumFunc {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn name(&self) -> &str {
+        "signum"
+    }
+
+    fn signature(&self) -> &Signature {
+        &self.signature
+    }
+
+    fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
+        match &arg_types[0] {
+            Float32 => Ok(Float32),
+            _ => Ok(Float64),
+        }
+    }
+
+    fn output_ordering(&self, input: &[ExprProperties]) -> Result<SortProperties> {
+        // Non-decreasing for all real numbers x.
+        Ok(input[0].sort_properties)
+    }
+
+    fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
+        make_scalar_function(signum, vec![])(args)
+    }
+}
+
+/// signum SQL function
+pub fn signum(args: &[ArrayRef]) -> Result<ArrayRef> {
+    match args[0].data_type() {
+        Float64 => Ok(Arc::new(make_function_scalar_inputs_return_type!(
+            &args[0],
+            "signum",
+            Float64Array,
+            Float64Array,
+            {
+                |x: f64| {
+                    if x == 0_f64 {
+                        0_f64
+                    } else {
+                        x.signum()
+                    }
+                }
+            }
+        )) as ArrayRef),
+
+        Float32 => Ok(Arc::new(make_function_scalar_inputs_return_type!(
+            &args[0],
+            "signum",
+            Float32Array,
+            Float32Array,
+            {
+                |x: f32| {
+                    if x == 0_f32 {
+                        0_f32
+                    } else {
+                        x.signum()
+                    }
+                }
+            }
+        )) as ArrayRef),
+
+        other => exec_err!("Unsupported data type {other:?} for function signum"),
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use std::sync::Arc;
+
+    use arrow::array::{Float32Array, Float64Array};
+
+    use datafusion_common::cast::{as_float32_array, as_float64_array};
+    use datafusion_expr::{ColumnarValue, ScalarUDFImpl};
+
+    use crate::math::signum::SignumFunc;
+
+    #[test]
+    fn test_signum_f32() {
+        let args = [ColumnarValue::Array(Arc::new(Float32Array::from(vec![
+            -1.0,
+            -0.0,
+            0.0,
+            1.0,
+            -0.01,
+            0.01,
+            f32::NAN,
+            f32::INFINITY,
+            f32::NEG_INFINITY,
+        ])))];
+
+        let result = SignumFunc::new()
+            .invoke(&args)
+            .expect("failed to initialize function signum");
+
+        match result {
+            ColumnarValue::Array(arr) => {
+                let floats = as_float32_array(&arr)
+                    .expect("failed to convert result to a Float32Array");
+
+                assert_eq!(floats.len(), 9);
+                assert_eq!(floats.value(0), -1.0);
+                assert_eq!(floats.value(1), 0.0);
+                assert_eq!(floats.value(2), 0.0);
+                assert_eq!(floats.value(3), 1.0);
+                assert_eq!(floats.value(4), -1.0);
+                assert_eq!(floats.value(5), 1.0);
+                assert!(floats.value(6).is_nan());
+                assert_eq!(floats.value(7), 1.0);
+                assert_eq!(floats.value(8), -1.0);
+            }
+            ColumnarValue::Scalar(_) => {
+                panic!("Expected an array value")
+            }
+        }
+    }
+
+    #[test]
+    fn test_signum_f64() {
+        let args = [ColumnarValue::Array(Arc::new(Float64Array::from(vec![
+            -1.0,
+            -0.0,
+            0.0,
+            1.0,
+            -0.01,
+            0.01,
+            f64::NAN,
+            f64::INFINITY,
+            f64::NEG_INFINITY,
+        ])))];
+
+        let result = SignumFunc::new()
+            .invoke(&args)
+            .expect("failed to initialize function signum");
+
+        match result {
+            ColumnarValue::Array(arr) => {
+                let floats = as_float64_array(&arr)
+                    .expect("failed to convert result to a Float32Array");
+
+                assert_eq!(floats.len(), 9);
+                assert_eq!(floats.value(0), -1.0);
+                assert_eq!(floats.value(1), 0.0);
+                assert_eq!(floats.value(2), 0.0);
+                assert_eq!(floats.value(3), 1.0);
+                assert_eq!(floats.value(4), -1.0);
+                assert_eq!(floats.value(5), 1.0);
+                assert!(floats.value(6).is_nan());
+                assert_eq!(floats.value(7), 1.0);
+                assert_eq!(floats.value(8), -1.0);
+            }
+            ColumnarValue::Scalar(_) => {
+                panic!("Expected an array value")
+            }
+        }
+    }
+}

datafusion/sqllogictest/test_files/scalar.slt

@@ -794,7 +794,7 @@ select round(column1, column2) from values (3.14, 2), (3.14, 3), (3.14, 21474836
 query RRR rowsort
 select signum(-2), signum(0), signum(2);
 ----
--1 1 1
+-1 0 1
 
 # signum scalar nulls
 query R rowsort