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

datafusion_functions/math/
lcm.rs
