datafusion_functions/math/
signum.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
7// with the License.  You may obtain a copy of the License at
8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing,
12// software distributed under the License is distributed on an
13// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18use std::sync::Arc;
19
20use arrow::array::AsArray;
21use arrow::datatypes::DataType::{Float32, Float64};
22use arrow::datatypes::{DataType, Float32Type, Float64Type};
23
24use datafusion_common::utils::take_function_args;
25use datafusion_common::{Result, ScalarValue, internal_err};
26use datafusion_expr::sort_properties::{ExprProperties, SortProperties};
27use datafusion_expr::{
28    ColumnarValue, Documentation, ScalarFunctionArgs, ScalarUDFImpl, Signature,
29    Volatility,
30};
31use datafusion_macros::user_doc;
32
33#[user_doc(
34    doc_section(label = "Math Functions"),
35    description = r#"Returns the sign of a number.
36Negative numbers return `-1`.
37Zero and positive numbers return `1`."#,
38    syntax_example = "signum(numeric_expression)",
39    standard_argument(name = "numeric_expression", prefix = "Numeric"),
40    sql_example = r#"```sql
41> SELECT signum(-42);
42+-------------+
43| signum(-42) |
44+-------------+
45| -1          |
46+-------------+
47```"#
48)]
49#[derive(Debug, PartialEq, Eq, Hash)]
50pub struct SignumFunc {
51    signature: Signature,
52}
53
54impl Default for SignumFunc {
55    fn default() -> Self {
56        SignumFunc::new()
57    }
58}
59
60impl SignumFunc {
61    pub fn new() -> Self {
62        use DataType::*;
63        Self {
64            signature: Signature::uniform(
65                1,
66                vec![Float64, Float32],
67                Volatility::Immutable,
68            ),
69        }
70    }
71}
72
73impl ScalarUDFImpl for SignumFunc {
74    fn name(&self) -> &str {
75        "signum"
76    }
77
78    fn signature(&self) -> &Signature {
79        &self.signature
80    }
81
82    fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
83        match &arg_types[0] {
84            Float32 => Ok(Float32),
85            _ => Ok(Float64),
86        }
87    }
88
89    fn is_strict(&self) -> bool {
90        true
91    }
92
93    fn output_ordering(&self, input: &[ExprProperties]) -> Result<SortProperties> {
94        // Non-decreasing for all real numbers x.
95        Ok(input[0].sort_properties)
96    }
97
98    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
99        let return_type = args.return_type().clone();
100        let [arg] = take_function_args(self.name(), args.args)?;
101
102        match arg {
103            ColumnarValue::Scalar(scalar) => {
104                if scalar.is_null() {
105                    return ColumnarValue::Scalar(ScalarValue::Null)
106                        .cast_to(&return_type, None);
107                }
108
109                match scalar {
110                    ScalarValue::Float64(Some(v)) => {
111                        let result = if v == 0.0 { 0.0 } else { v.signum() };
112                        Ok(ColumnarValue::Scalar(ScalarValue::Float64(Some(result))))
113                    }
114                    ScalarValue::Float32(Some(v)) => {
115                        let result = if v == 0.0 { 0.0 } else { v.signum() };
116                        Ok(ColumnarValue::Scalar(ScalarValue::Float32(Some(result))))
117                    }
118                    _ => {
119                        internal_err!(
120                            "Unexpected scalar type for signum: {:?}",
121                            scalar.data_type()
122                        )
123                    }
124                }
125            }
126            ColumnarValue::Array(array) => match array.data_type() {
127                Float64 => Ok(ColumnarValue::Array(Arc::new(
128                    array.as_primitive::<Float64Type>().unary::<_, Float64Type>(
129                        |x: f64| {
130                            if x == 0.0 { 0.0 } else { x.signum() }
131                        },
132                    ),
133                ))),
134                Float32 => Ok(ColumnarValue::Array(Arc::new(
135                    array.as_primitive::<Float32Type>().unary::<_, Float32Type>(
136                        |x: f32| {
137                            if x == 0.0 { 0.0 } else { x.signum() }
138                        },
139                    ),
140                ))),
141                other => {
142                    internal_err!("Unsupported data type {other:?} for function signum")
143                }
144            },
145        }
146    }
147
148    fn documentation(&self) -> Option<&Documentation> {
149        self.doc()
150    }
151}
152
153#[cfg(test)]
154mod test {
155    use std::sync::Arc;
156
157    use arrow::array::{ArrayRef, Float32Array, Float64Array};
158    use arrow::datatypes::{DataType, Field};
159    use datafusion_common::cast::{as_float32_array, as_float64_array};
160    use datafusion_common::config::ConfigOptions;
161    use datafusion_expr::{ColumnarValue, ScalarFunctionArgs, ScalarUDFImpl};
162
163    use crate::math::signum::SignumFunc;
164
165    #[test]
166    fn test_signum_f32() {
167        let array = Arc::new(Float32Array::from(vec![
168            -1.0,
169            -0.0,
170            0.0,
171            1.0,
172            -0.01,
173            0.01,
174            f32::NAN,
175            f32::INFINITY,
176            f32::NEG_INFINITY,
177        ]));
178        let arg_fields = vec![Field::new("a", DataType::Float32, false).into()];
179        let args = ScalarFunctionArgs {
180            args: vec![ColumnarValue::Array(Arc::clone(&array) as ArrayRef)],
181            arg_fields,
182            number_rows: array.len(),
183            return_field: Field::new("f", DataType::Float32, true).into(),
184            config_options: Arc::new(ConfigOptions::default()),
185        };
186        let result = SignumFunc::new()
187            .invoke_with_args(args)
188            .expect("failed to initialize function signum");
189
190        match result {
191            ColumnarValue::Array(arr) => {
192                let floats = as_float32_array(&arr)
193                    .expect("failed to convert result to a Float32Array");
194
195                assert_eq!(floats.len(), 9);
196                assert_eq!(floats.value(0), -1.0);
197                assert_eq!(floats.value(1), 0.0);
198                assert_eq!(floats.value(2), 0.0);
199                assert_eq!(floats.value(3), 1.0);
200                assert_eq!(floats.value(4), -1.0);
201                assert_eq!(floats.value(5), 1.0);
202                assert!(floats.value(6).is_nan());
203                assert_eq!(floats.value(7), 1.0);
204                assert_eq!(floats.value(8), -1.0);
205            }
206            ColumnarValue::Scalar(_) => {
207                panic!("Expected an array value")
208            }
209        }
210    }
211
212    #[test]
213    fn test_signum_f64() {
214        let array = Arc::new(Float64Array::from(vec![
215            -1.0,
216            -0.0,
217            0.0,
218            1.0,
219            -0.01,
220            0.01,
221            f64::NAN,
222            f64::INFINITY,
223            f64::NEG_INFINITY,
224        ]));
225        let arg_fields = vec![Field::new("a", DataType::Float64, false).into()];
226        let args = ScalarFunctionArgs {
227            args: vec![ColumnarValue::Array(Arc::clone(&array) as ArrayRef)],
228            arg_fields,
229            number_rows: array.len(),
230            return_field: Field::new("f", DataType::Float64, true).into(),
231            config_options: Arc::new(ConfigOptions::default()),
232        };
233        let result = SignumFunc::new()
234            .invoke_with_args(args)
235            .expect("failed to initialize function signum");
236
237        match result {
238            ColumnarValue::Array(arr) => {
239                let floats = as_float64_array(&arr)
240                    .expect("failed to convert result to a Float32Array");
241
242                assert_eq!(floats.len(), 9);
243                assert_eq!(floats.value(0), -1.0);
244                assert_eq!(floats.value(1), 0.0);
245                assert_eq!(floats.value(2), 0.0);
246                assert_eq!(floats.value(3), 1.0);
247                assert_eq!(floats.value(4), -1.0);
248                assert_eq!(floats.value(5), 1.0);
249                assert!(floats.value(6).is_nan());
250                assert_eq!(floats.value(7), 1.0);
251                assert_eq!(floats.value(8), -1.0);
252            }
253            ColumnarValue::Scalar(_) => {
254                panic!("Expected an array value")
255            }
256        }
257    }
258}
datafusion_functions/math/signum.rs

datafusion_functions/math/
signum.rs
