datafusion_functions/math/
factorial.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 arrow::array::{ArrayRef, AsArray, Int64Array};
19use std::any::Any;
20use std::sync::Arc;
21
22use arrow::datatypes::DataType::Int64;
23use arrow::datatypes::{DataType, Int64Type};
24
25use crate::utils::make_scalar_function;
26use datafusion_common::{Result, exec_err};
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 = "Factorial. Returns 1 if value is less than 2.",
36    syntax_example = "factorial(numeric_expression)",
37    sql_example = r#"```sql
38> SELECT factorial(5);
39+---------------+
40| factorial(5)  |
41+---------------+
42| 120           |
43+---------------+
44```"#,
45    standard_argument(name = "numeric_expression", prefix = "Numeric")
46)]
47#[derive(Debug, PartialEq, Eq, Hash)]
48pub struct FactorialFunc {
49    signature: Signature,
50}
51
52impl Default for FactorialFunc {
53    fn default() -> Self {
54        FactorialFunc::new()
55    }
56}
57
58impl FactorialFunc {
59    pub fn new() -> Self {
60        Self {
61            signature: Signature::uniform(1, vec![Int64], Volatility::Immutable),
62        }
63    }
64}
65
66impl ScalarUDFImpl for FactorialFunc {
67    fn as_any(&self) -> &dyn Any {
68        self
69    }
70
71    fn name(&self) -> &str {
72        "factorial"
73    }
74
75    fn signature(&self) -> &Signature {
76        &self.signature
77    }
78
79    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
80        Ok(Int64)
81    }
82
83    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
84        make_scalar_function(factorial, vec![])(&args.args)
85    }
86
87    fn documentation(&self) -> Option<&Documentation> {
88        self.doc()
89    }
90}
91
92const FACTORIALS: [i64; 21] = [
93    1,
94    1,
95    2,
96    6,
97    24,
98    120,
99    720,
100    5040,
101    40320,
102    362880,
103    3628800,
104    39916800,
105    479001600,
106    6227020800,
107    87178291200,
108    1307674368000,
109    20922789888000,
110    355687428096000,
111    6402373705728000,
112    121645100408832000,
113    2432902008176640000,
114]; // if return type changes, this constant needs to be updated accordingly
115
116/// Factorial SQL function
117fn factorial(args: &[ArrayRef]) -> Result<ArrayRef> {
118    match args[0].data_type() {
119        Int64 => {
120            let result: Int64Array =
121                args[0].as_primitive::<Int64Type>().try_unary(|a| {
122                    if a < 0 {
123                        Ok(1)
124                    } else if a < FACTORIALS.len() as i64 {
125                        Ok(FACTORIALS[a as usize])
126                    } else {
127                        exec_err!("Overflow happened on FACTORIAL({a})")
128                    }
129                })?;
130            Ok(Arc::new(result) as ArrayRef)
131        }
132        other => exec_err!("Unsupported data type {other:?} for function factorial."),
133    }
134}
135
136#[cfg(test)]
137mod test {
138    use super::*;
139    use datafusion_common::cast::as_int64_array;
140
141    #[test]
142    fn test_factorial_i64() {
143        let args: Vec<ArrayRef> = vec![
144            Arc::new(Int64Array::from(vec![0, 1, 2, 4, 20, -1])), // input
145        ];
146
147        let result = factorial(&args).expect("failed to initialize function factorial");
148        let ints =
149            as_int64_array(&result).expect("failed to initialize function factorial");
150
151        let expected = Int64Array::from(vec![1, 1, 2, 24, 2432902008176640000, 1]);
152
153        assert_eq!(ints, &expected);
154    }
155
156    #[test]
157    fn test_overflow() {
158        let args: Vec<ArrayRef> = vec![
159            Arc::new(Int64Array::from(vec![21])), // input
160        ];
161
162        let result = factorial(&args);
163        assert!(result.is_err());
164    }
165}
datafusion_functions/math/factorial.rs

datafusion_functions/math/
factorial.rs
