datafusion_functions/math/
lcm.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, Int64Array};
22use arrow::datatypes::DataType;
23use arrow::datatypes::DataType::Int64;
24
25use arrow::error::ArrowError;
26use datafusion_common::{arrow_datafusion_err, exec_err, DataFusionError, Result};
27use datafusion_expr::{
28    ColumnarValue, Documentation, ScalarFunctionArgs, ScalarUDFImpl, Signature,
29    Volatility,
30};
31use datafusion_macros::user_doc;
32
33use super::gcd::unsigned_gcd;
34use crate::utils::make_scalar_function;
35
36#[user_doc(
37    doc_section(label = "Math Functions"),
38    description = "Returns the least common multiple of `expression_x` and `expression_y`. Returns 0 if either input is zero.",
39    syntax_example = "lcm(expression_x, expression_y)",
40    sql_example = r#"```sql
41> SELECT lcm(4, 5);
42+----------+
43| lcm(4,5) |
44+----------+
45| 20       |
46+----------+
47```"#,
48    standard_argument(name = "expression_x", prefix = "First numeric"),
49    standard_argument(name = "expression_y", prefix = "Second numeric")
50)]
51#[derive(Debug, PartialEq, Eq, Hash)]
52pub struct LcmFunc {
53    signature: Signature,
54}
55
56impl Default for LcmFunc {
57    fn default() -> Self {
58        LcmFunc::new()
59    }
60}
61
62impl LcmFunc {
63    pub fn new() -> Self {
64        use DataType::*;
65        Self {
66            signature: Signature::uniform(2, vec![Int64], Volatility::Immutable),
67        }
68    }
69}
70
71impl ScalarUDFImpl for LcmFunc {
72    fn as_any(&self) -> &dyn Any {
73        self
74    }
75
76    fn name(&self) -> &str {
77        "lcm"
78    }
79
80    fn signature(&self) -> &Signature {
81        &self.signature
82    }
83
84    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
85        Ok(Int64)
86    }
87
88    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
89        make_scalar_function(lcm, vec![])(&args.args)
90    }
91
92    fn documentation(&self) -> Option<&Documentation> {
93        self.doc()
94    }
95}
96
97/// Lcm SQL function
98fn lcm(args: &[ArrayRef]) -> Result<ArrayRef> {
99    let compute_lcm = |x: i64, y: i64| {
100        if x == 0 || y == 0 {
101            return Ok(0);
102        }
103
104        // lcm(x, y) = |x| * |y| / gcd(|x|, |y|)
105        let a = x.unsigned_abs();
106        let b = y.unsigned_abs();
107        let gcd = unsigned_gcd(a, b);
108        // gcd is not zero since both a and b are not zero, so the division is safe.
109        (a / gcd)
110            .checked_mul(b)
111            .and_then(|v| i64::try_from(v).ok())
112            .ok_or_else(|| {
113                arrow_datafusion_err!(ArrowError::ComputeError(format!(
114                    "Signed integer overflow in LCM({x}, {y})"
115                )))
116            })
117    };
118
119    match args[0].data_type() {
120        Int64 => {
121            let arg1 = downcast_named_arg!(&args[0], "x", Int64Array);
122            let arg2 = downcast_named_arg!(&args[1], "y", Int64Array);
123
124            Ok(arg1
125                .iter()
126                .zip(arg2.iter())
127                .map(|(a1, a2)| match (a1, a2) {
128                    (Some(a1), Some(a2)) => Ok(Some(compute_lcm(a1, a2)?)),
129                    _ => Ok(None),
130                })
131                .collect::<Result<Int64Array>>()
132                .map(Arc::new)? as ArrayRef)
133        }
134        other => exec_err!("Unsupported data type {other:?} for function lcm"),
135    }
136}
137
138#[cfg(test)]
139mod test {
140    use std::sync::Arc;
141
142    use arrow::array::{ArrayRef, Int64Array};
143
144    use datafusion_common::cast::as_int64_array;
145
146    use crate::math::lcm::lcm;
147
148    #[test]
149    fn test_lcm_i64() {
150        let args: Vec<ArrayRef> = vec![
151            Arc::new(Int64Array::from(vec![0, 3, 25, -16])), // x
152            Arc::new(Int64Array::from(vec![0, -2, 15, 8])),  // y
153        ];
154
155        let result = lcm(&args).expect("failed to initialize function lcm");
156        let ints = as_int64_array(&result).expect("failed to initialize function lcm");
157
158        assert_eq!(ints.len(), 4);
159        assert_eq!(ints.value(0), 0);
160        assert_eq!(ints.value(1), 6);
161        assert_eq!(ints.value(2), 75);
162        assert_eq!(ints.value(3), 16);
163    }
164}
datafusion_functions/math/lcm.rs

datafusion_functions/math/
lcm.rs
