datafusion_functions/math/
random.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::Float64Array;
22use arrow::datatypes::DataType;
23use arrow::datatypes::DataType::Float64;
24use rand::{rng, Rng};
25
26use datafusion_common::{internal_err, Result};
27use datafusion_expr::{ColumnarValue, ScalarFunctionArgs};
28use datafusion_expr::{Documentation, ScalarUDFImpl, Signature, Volatility};
29use datafusion_macros::user_doc;
30
31#[user_doc(
32    doc_section(label = "Math Functions"),
33    description = r#"Returns a random float value in the range [0, 1).
34The random seed is unique to each row."#,
35    syntax_example = "random()",
36    sql_example = r#"```sql
37> SELECT random();
38+------------------+
39| random()         |
40+------------------+
41| 0.7389238902938  |
42+------------------+
43```"#
44)]
45#[derive(Debug, PartialEq, Eq, Hash)]
46pub struct RandomFunc {
47    signature: Signature,
48}
49
50impl Default for RandomFunc {
51    fn default() -> Self {
52        RandomFunc::new()
53    }
54}
55
56impl RandomFunc {
57    pub fn new() -> Self {
58        Self {
59            signature: Signature::nullary(Volatility::Volatile),
60        }
61    }
62}
63
64impl ScalarUDFImpl for RandomFunc {
65    fn as_any(&self) -> &dyn Any {
66        self
67    }
68
69    fn name(&self) -> &str {
70        "random"
71    }
72
73    fn signature(&self) -> &Signature {
74        &self.signature
75    }
76
77    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
78        Ok(Float64)
79    }
80
81    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
82        if !args.args.is_empty() {
83            return internal_err!("{} function does not accept arguments", self.name());
84        }
85        let mut rng = rng();
86        let mut values = vec![0.0; args.number_rows];
87        // Equivalent to set each element with rng.random_range(0.0..1.0), but more efficient
88        rng.fill(&mut values[..]);
89        let array = Float64Array::from(values);
90
91        Ok(ColumnarValue::Array(Arc::new(array)))
92    }
93
94    fn documentation(&self) -> Option<&Documentation> {
95        self.doc()
96    }
97}
datafusion_functions/math/random.rs

datafusion_functions/math/
random.rs
