datafusion_functions/string/
chr.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;
22use arrow::array::GenericStringBuilder;
23use arrow::datatypes::DataType;
24use arrow::datatypes::DataType::Int64;
25use arrow::datatypes::DataType::Utf8;
26
27use crate::utils::make_scalar_function;
28use datafusion_common::cast::as_int64_array;
29use datafusion_common::{exec_err, Result};
30use datafusion_expr::{ColumnarValue, Documentation, Volatility};
31use datafusion_expr::{ScalarFunctionArgs, ScalarUDFImpl, Signature};
32use datafusion_macros::user_doc;
33
34/// Returns the character with the given code. chr(0) is disallowed because text data types cannot store that character.
35/// chr(65) = 'A'
36pub fn chr(args: &[ArrayRef]) -> Result<ArrayRef> {
37    let integer_array = as_int64_array(&args[0])?;
38
39    let mut builder = GenericStringBuilder::<i32>::with_capacity(
40        integer_array.len(),
41        // 1 byte per character, assuming that is the common case
42        integer_array.len(),
43    );
44
45    let mut buf = [0u8; 4];
46
47    for integer in integer_array {
48        match integer {
49            Some(integer) => {
50                if integer == 0 {
51                    return exec_err!("null character not permitted.");
52                } else {
53                    match core::char::from_u32(integer as u32) {
54                        Some(c) => {
55                            builder.append_value(c.encode_utf8(&mut buf));
56                        }
57                        None => {
58                            return exec_err!(
59                                "requested character too large for encoding."
60                            );
61                        }
62                    }
63                }
64            }
65            None => {
66                builder.append_null();
67            }
68        }
69    }
70
71    let result = builder.finish();
72
73    Ok(Arc::new(result) as ArrayRef)
74}
75
76#[user_doc(
77    doc_section(label = "String Functions"),
78    description = "Returns the character with the specified ASCII or Unicode code value.",
79    syntax_example = "chr(expression)",
80    sql_example = r#"```sql
81> select chr(128640);
82+--------------------+
83| chr(Int64(128640)) |
84+--------------------+
85| 🚀                 |
86+--------------------+
87```"#,
88    standard_argument(name = "expression", prefix = "String"),
89    related_udf(name = "ascii")
90)]
91#[derive(Debug)]
92pub struct ChrFunc {
93    signature: Signature,
94}
95
96impl Default for ChrFunc {
97    fn default() -> Self {
98        Self::new()
99    }
100}
101
102impl ChrFunc {
103    pub fn new() -> Self {
104        Self {
105            signature: Signature::uniform(1, vec![Int64], Volatility::Immutable),
106        }
107    }
108}
109
110impl ScalarUDFImpl for ChrFunc {
111    fn as_any(&self) -> &dyn Any {
112        self
113    }
114
115    fn name(&self) -> &str {
116        "chr"
117    }
118
119    fn signature(&self) -> &Signature {
120        &self.signature
121    }
122
123    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
124        Ok(Utf8)
125    }
126
127    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
128        make_scalar_function(chr, vec![])(&args.args)
129    }
130
131    fn documentation(&self) -> Option<&Documentation> {
132        self.doc()
133    }
134}
datafusion_functions/string/chr.rs

datafusion_functions/string/
chr.rs
