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::any::Any;
19use std::sync::Arc;
20
21use arrow::array::{ArrayRef, AsArray};
22use arrow::datatypes::DataType::{Float32, Float64};
23use arrow::datatypes::{DataType, Float32Type, Float64Type};
24
25use datafusion_common::{exec_err, Result};
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
33use crate::utils::make_scalar_function;
34
35#[user_doc(
36    doc_section(label = "Math Functions"),
37    description = r#"Returns the sign of a number.
38Negative numbers return `-1`.
39Zero and positive numbers return `1`."#,
40    syntax_example = "signum(numeric_expression)",
41    standard_argument(name = "numeric_expression", prefix = "Numeric"),
42    sql_example = r#"```sql
43> SELECT signum(-42);
44+-------------+
45| signum(-42) |
46+-------------+
47| -1          |
48+-------------+
49```"#
50)]
51#[derive(Debug, PartialEq, Eq, Hash)]
52pub struct SignumFunc {
53    signature: Signature,
54}
55
56impl Default for SignumFunc {
57    fn default() -> Self {
58        SignumFunc::new()
59    }
60}
61
62impl SignumFunc {
63    pub fn new() -> Self {
64        use DataType::*;
65        Self {
66            signature: Signature::uniform(
67                1,
68                vec![Float64, Float32],
69                Volatility::Immutable,
70            ),
71        }
72    }
73}
74
75impl ScalarUDFImpl for SignumFunc {
76    fn as_any(&self) -> &dyn Any {
77        self
78    }
79
80    fn name(&self) -> &str {
81        "signum"
82    }
83
84    fn signature(&self) -> &Signature {
85        &self.signature
86    }
87
88    fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
89        match &arg_types[0] {
90            Float32 => Ok(Float32),
91            _ => Ok(Float64),
92        }
93    }
94
95    fn output_ordering(&self, input: &[ExprProperties]) -> Result<SortProperties> {
96        // Non-decreasing for all real numbers x.
97        Ok(input[0].sort_properties)
98    }
99
100    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
101        make_scalar_function(signum, vec![])(&args.args)
102    }
103
104    fn documentation(&self) -> Option<&Documentation> {
105        self.doc()
106    }
107}
108
109/// signum SQL function
110pub fn signum(args: &[ArrayRef]) -> Result<ArrayRef> {
111    match args[0].data_type() {
112        Float64 => Ok(Arc::new(
113            args[0]
114                .as_primitive::<Float64Type>()
115                .unary::<_, Float64Type>(
116                    |x: f64| {
117                        if x == 0_f64 {
118                            0_f64
119                        } else {
120                            x.signum()
121                        }
122                    },
123                ),
124        ) as ArrayRef),
125
126        Float32 => Ok(Arc::new(
127            args[0]
128                .as_primitive::<Float32Type>()
129                .unary::<_, Float32Type>(
130                    |x: f32| {
131                        if x == 0_f32 {
132                            0_f32
133                        } else {
134                            x.signum()
135                        }
136                    },
137                ),
138        ) as ArrayRef),
139
140        other => exec_err!("Unsupported data type {other:?} for function signum"),
141    }
142}
143
144#[cfg(test)]
145mod test {
146    use std::sync::Arc;
147
148    use arrow::array::{ArrayRef, Float32Array, Float64Array};
149    use arrow::datatypes::{DataType, Field};
150    use datafusion_common::cast::{as_float32_array, as_float64_array};
151    use datafusion_common::config::ConfigOptions;
152    use datafusion_expr::{ColumnarValue, ScalarFunctionArgs, ScalarUDFImpl};
153
154    use crate::math::signum::SignumFunc;
155
156    #[test]
157    fn test_signum_f32() {
158        let array = Arc::new(Float32Array::from(vec![
159            -1.0,
160            -0.0,
161            0.0,
162            1.0,
163            -0.01,
164            0.01,
165            f32::NAN,
166            f32::INFINITY,
167            f32::NEG_INFINITY,
168        ]));
169        let arg_fields = vec![Field::new("a", DataType::Float32, false).into()];
170        let args = ScalarFunctionArgs {
171            args: vec![ColumnarValue::Array(Arc::clone(&array) as ArrayRef)],
172            arg_fields,
173            number_rows: array.len(),
174            return_field: Field::new("f", DataType::Float32, true).into(),
175            config_options: Arc::new(ConfigOptions::default()),
176        };
177        let result = SignumFunc::new()
178            .invoke_with_args(args)
179            .expect("failed to initialize function signum");
180
181        match result {
182            ColumnarValue::Array(arr) => {
183                let floats = as_float32_array(&arr)
184                    .expect("failed to convert result to a Float32Array");
185
186                assert_eq!(floats.len(), 9);
187                assert_eq!(floats.value(0), -1.0);
188                assert_eq!(floats.value(1), 0.0);
189                assert_eq!(floats.value(2), 0.0);
190                assert_eq!(floats.value(3), 1.0);
191                assert_eq!(floats.value(4), -1.0);
192                assert_eq!(floats.value(5), 1.0);
193                assert!(floats.value(6).is_nan());
194                assert_eq!(floats.value(7), 1.0);
195                assert_eq!(floats.value(8), -1.0);
196            }
197            ColumnarValue::Scalar(_) => {
198                panic!("Expected an array value")
199            }
200        }
201    }
202
203    #[test]
204    fn test_signum_f64() {
205        let array = Arc::new(Float64Array::from(vec![
206            -1.0,
207            -0.0,
208            0.0,
209            1.0,
210            -0.01,
211            0.01,
212            f64::NAN,
213            f64::INFINITY,
214            f64::NEG_INFINITY,
215        ]));
216        let arg_fields = vec![Field::new("a", DataType::Float64, false).into()];
217        let args = ScalarFunctionArgs {
218            args: vec![ColumnarValue::Array(Arc::clone(&array) as ArrayRef)],
219            arg_fields,
220            number_rows: array.len(),
221            return_field: Field::new("f", DataType::Float64, true).into(),
222            config_options: Arc::new(ConfigOptions::default()),
223        };
224        let result = SignumFunc::new()
225            .invoke_with_args(args)
226            .expect("failed to initialize function signum");
227
228        match result {
229            ColumnarValue::Array(arr) => {
230                let floats = as_float64_array(&arr)
231                    .expect("failed to convert result to a Float32Array");
232
233                assert_eq!(floats.len(), 9);
234                assert_eq!(floats.value(0), -1.0);
235                assert_eq!(floats.value(1), 0.0);
236                assert_eq!(floats.value(2), 0.0);
237                assert_eq!(floats.value(3), 1.0);
238                assert_eq!(floats.value(4), -1.0);
239                assert_eq!(floats.value(5), 1.0);
240                assert!(floats.value(6).is_nan());
241                assert_eq!(floats.value(7), 1.0);
242                assert_eq!(floats.value(8), -1.0);
243            }
244            ColumnarValue::Scalar(_) => {
245                panic!("Expected an array value")
246            }
247        }
248    }
249}
datafusion_functions/math/signum.rs

datafusion_functions/math/
signum.rs
