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::AsArray;
22use arrow::datatypes::DataType::{Float32, Float64};
23use arrow::datatypes::{DataType, Float32Type, Float64Type};
24
25use datafusion_common::utils::take_function_args;
26use datafusion_common::{Result, ScalarValue, internal_err};
27use datafusion_expr::sort_properties::{ExprProperties, SortProperties};
28use datafusion_expr::{
29    ColumnarValue, Documentation, ScalarFunctionArgs, ScalarUDFImpl, Signature,
30    Volatility,
31};
32use datafusion_macros::user_doc;
33
34#[user_doc(
35    doc_section(label = "Math Functions"),
36    description = r#"Returns the sign of a number.
37Negative numbers return `-1`.
38Zero and positive numbers return `1`."#,
39    syntax_example = "signum(numeric_expression)",
40    standard_argument(name = "numeric_expression", prefix = "Numeric"),
41    sql_example = r#"```sql
42> SELECT signum(-42);
43+-------------+
44| signum(-42) |
45+-------------+
46| -1          |
47+-------------+
48```"#
49)]
50#[derive(Debug, PartialEq, Eq, Hash)]
51pub struct SignumFunc {
52    signature: Signature,
53}
54
55impl Default for SignumFunc {
56    fn default() -> Self {
57        SignumFunc::new()
58    }
59}
60
61impl SignumFunc {
62    pub fn new() -> Self {
63        use DataType::*;
64        Self {
65            signature: Signature::uniform(
66                1,
67                vec![Float64, Float32],
68                Volatility::Immutable,
69            ),
70        }
71    }
72}
73
74impl ScalarUDFImpl for SignumFunc {
75    fn as_any(&self) -> &dyn Any {
76        self
77    }
78
79    fn name(&self) -> &str {
80        "signum"
81    }
82
83    fn signature(&self) -> &Signature {
84        &self.signature
85    }
86
87    fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
88        match &arg_types[0] {
89            Float32 => Ok(Float32),
90            _ => Ok(Float64),
91        }
92    }
93
94    fn output_ordering(&self, input: &[ExprProperties]) -> Result<SortProperties> {
95        // Non-decreasing for all real numbers x.
96        Ok(input[0].sort_properties)
97    }
98
99    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
100        let return_type = args.return_type().clone();
101        let [arg] = take_function_args(self.name(), args.args)?;
102
103        match arg {
104            ColumnarValue::Scalar(scalar) => {
105                if scalar.is_null() {
106                    return ColumnarValue::Scalar(ScalarValue::Null)
107                        .cast_to(&return_type, None);
108                }
109
110                match scalar {
111                    ScalarValue::Float64(Some(v)) => {
112                        let result = if v == 0.0 { 0.0 } else { v.signum() };
113                        Ok(ColumnarValue::Scalar(ScalarValue::Float64(Some(result))))
114                    }
115                    ScalarValue::Float32(Some(v)) => {
116                        let result = if v == 0.0 { 0.0 } else { v.signum() };
117                        Ok(ColumnarValue::Scalar(ScalarValue::Float32(Some(result))))
118                    }
119                    _ => {
120                        internal_err!(
121                            "Unexpected scalar type for signum: {:?}",
122                            scalar.data_type()
123                        )
124                    }
125                }
126            }
127            ColumnarValue::Array(array) => match array.data_type() {
128                Float64 => Ok(ColumnarValue::Array(Arc::new(
129                    array.as_primitive::<Float64Type>().unary::<_, Float64Type>(
130                        |x: f64| {
131                            if x == 0.0 { 0.0 } else { x.signum() }
132                        },
133                    ),
134                ))),
135                Float32 => Ok(ColumnarValue::Array(Arc::new(
136                    array.as_primitive::<Float32Type>().unary::<_, Float32Type>(
137                        |x: f32| {
138                            if x == 0.0 { 0.0 } else { x.signum() }
139                        },
140                    ),
141                ))),
142                other => {
143                    internal_err!("Unsupported data type {other:?} for function signum")
144                }
145            },
146        }
147    }
148
149    fn documentation(&self) -> Option<&Documentation> {
150        self.doc()
151    }
152}
153
154#[cfg(test)]
155mod test {
156    use std::sync::Arc;
157
158    use arrow::array::{ArrayRef, Float32Array, Float64Array};
159    use arrow::datatypes::{DataType, Field};
160    use datafusion_common::cast::{as_float32_array, as_float64_array};
161    use datafusion_common::config::ConfigOptions;
162    use datafusion_expr::{ColumnarValue, ScalarFunctionArgs, ScalarUDFImpl};
163
164    use crate::math::signum::SignumFunc;
165
166    #[test]
167    fn test_signum_f32() {
168        let array = Arc::new(Float32Array::from(vec![
169            -1.0,
170            -0.0,
171            0.0,
172            1.0,
173            -0.01,
174            0.01,
175            f32::NAN,
176            f32::INFINITY,
177            f32::NEG_INFINITY,
178        ]));
179        let arg_fields = vec![Field::new("a", DataType::Float32, false).into()];
180        let args = ScalarFunctionArgs {
181            args: vec![ColumnarValue::Array(Arc::clone(&array) as ArrayRef)],
182            arg_fields,
183            number_rows: array.len(),
184            return_field: Field::new("f", DataType::Float32, true).into(),
185            config_options: Arc::new(ConfigOptions::default()),
186        };
187        let result = SignumFunc::new()
188            .invoke_with_args(args)
189            .expect("failed to initialize function signum");
190
191        match result {
192            ColumnarValue::Array(arr) => {
193                let floats = as_float32_array(&arr)
194                    .expect("failed to convert result to a Float32Array");
195
196                assert_eq!(floats.len(), 9);
197                assert_eq!(floats.value(0), -1.0);
198                assert_eq!(floats.value(1), 0.0);
199                assert_eq!(floats.value(2), 0.0);
200                assert_eq!(floats.value(3), 1.0);
201                assert_eq!(floats.value(4), -1.0);
202                assert_eq!(floats.value(5), 1.0);
203                assert!(floats.value(6).is_nan());
204                assert_eq!(floats.value(7), 1.0);
205                assert_eq!(floats.value(8), -1.0);
206            }
207            ColumnarValue::Scalar(_) => {
208                panic!("Expected an array value")
209            }
210        }
211    }
212
213    #[test]
214    fn test_signum_f64() {
215        let array = Arc::new(Float64Array::from(vec![
216            -1.0,
217            -0.0,
218            0.0,
219            1.0,
220            -0.01,
221            0.01,
222            f64::NAN,
223            f64::INFINITY,
224            f64::NEG_INFINITY,
225        ]));
226        let arg_fields = vec![Field::new("a", DataType::Float64, false).into()];
227        let args = ScalarFunctionArgs {
228            args: vec![ColumnarValue::Array(Arc::clone(&array) as ArrayRef)],
229            arg_fields,
230            number_rows: array.len(),
231            return_field: Field::new("f", DataType::Float64, true).into(),
232            config_options: Arc::new(ConfigOptions::default()),
233        };
234        let result = SignumFunc::new()
235            .invoke_with_args(args)
236            .expect("failed to initialize function signum");
237
238        match result {
239            ColumnarValue::Array(arr) => {
240                let floats = as_float64_array(&arr)
241                    .expect("failed to convert result to a Float32Array");
242
243                assert_eq!(floats.len(), 9);
244                assert_eq!(floats.value(0), -1.0);
245                assert_eq!(floats.value(1), 0.0);
246                assert_eq!(floats.value(2), 0.0);
247                assert_eq!(floats.value(3), 1.0);
248                assert_eq!(floats.value(4), -1.0);
249                assert_eq!(floats.value(5), 1.0);
250                assert!(floats.value(6).is_nan());
251                assert_eq!(floats.value(7), 1.0);
252                assert_eq!(floats.value(8), -1.0);
253            }
254            ColumnarValue::Scalar(_) => {
255                panic!("Expected an array value")
256            }
257        }
258    }
259}
datafusion_functions/math/signum.rs

datafusion_functions/math/
signum.rs
