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::sync::Arc;
20
21use arrow::datatypes::DataType::Int64;
22use arrow::datatypes::{DataType, Int64Type};
23
24use datafusion_common::{
25    Result, ScalarValue, exec_err, internal_err, utils::take_function_args,
26};
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 of a non-negative integer. Errors if the argument is negative or the result overflows.",
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 name(&self) -> &str {
68        "factorial"
69    }
70
71    fn signature(&self) -> &Signature {
72        &self.signature
73    }
74
75    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
76        Ok(Int64)
77    }
78
79    fn is_strict(&self) -> bool {
80        true
81    }
82
83    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
84        let [arg] = take_function_args(self.name(), args.args)?;
85
86        match arg {
87            ColumnarValue::Scalar(scalar) => {
88                if scalar.is_null() {
89                    return Ok(ColumnarValue::Scalar(ScalarValue::Int64(None)));
90                }
91
92                match scalar {
93                    ScalarValue::Int64(Some(v)) => {
94                        let result = compute_factorial(v)?;
95                        Ok(ColumnarValue::Scalar(ScalarValue::Int64(Some(result))))
96                    }
97                    _ => {
98                        internal_err!(
99                            "Unexpected data type {:?} for function factorial",
100                            scalar.data_type()
101                        )
102                    }
103                }
104            }
105            ColumnarValue::Array(array) => match array.data_type() {
106                Int64 => {
107                    let result: Int64Array = array
108                        .as_primitive::<Int64Type>()
109                        .try_unary(compute_factorial)?;
110                    Ok(ColumnarValue::Array(Arc::new(result) as ArrayRef))
111                }
112                other => {
113                    internal_err!("Unexpected data type {other:?} for function factorial")
114                }
115            },
116        }
117    }
118
119    fn documentation(&self) -> Option<&Documentation> {
120        self.doc()
121    }
122}
123
124const FACTORIALS: [i64; 21] = [
125    1,
126    1,
127    2,
128    6,
129    24,
130    120,
131    720,
132    5040,
133    40320,
134    362880,
135    3628800,
136    39916800,
137    479001600,
138    6227020800,
139    87178291200,
140    1307674368000,
141    20922789888000,
142    355687428096000,
143    6402373705728000,
144    121645100408832000,
145    2432902008176640000,
146]; // if return type changes, this constant needs to be updated accordingly
147
148fn compute_factorial(n: i64) -> Result<i64> {
149    if n < 0 {
150        exec_err!("factorial of a negative number is undefined")
151    } else if n < FACTORIALS.len() as i64 {
152        Ok(FACTORIALS[n as usize])
153    } else {
154        exec_err!("Overflow happened on FACTORIAL({n})")
155    }
156}
datafusion_functions/math/factorial.rs

datafusion_functions/math/
factorial.rs
