1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

//! [`ScalarUDFImpl`] definitions for array functions.

use arrow::datatypes::DataType;
use datafusion_common::{plan_err, DataFusionError};
use datafusion_expr::expr::ScalarFunction;
use datafusion_expr::Expr;
use datafusion_expr::{ColumnarValue, ScalarUDFImpl, Signature, Volatility};
use std::any::Any;

// Create static instances of ScalarUDFs for each function
make_udf_function!(ArrayToString,
    array_to_string,
    array delimiter, // arg name
    "converts each element to its text representation.", // doc
    array_to_string_udf // internal function name
);

#[derive(Debug)]
pub(super) struct ArrayToString {
    signature: Signature,
    aliases: Vec<String>,
}

impl ArrayToString {
    pub fn new() -> Self {
        Self {
            signature: Signature::variadic_any(Volatility::Immutable),
            aliases: vec![
                String::from("array_to_string"),
                String::from("list_to_string"),
                String::from("array_join"),
                String::from("list_join"),
            ],
        }
    }
}

impl ScalarUDFImpl for ArrayToString {
    fn as_any(&self) -> &dyn Any {
        self
    }
    fn name(&self) -> &str {
        "array_to_string"
    }

    fn signature(&self) -> &Signature {
        &self.signature
    }

    fn return_type(&self, arg_types: &[DataType]) -> datafusion_common::Result<DataType> {
        use DataType::*;
        Ok(match arg_types[0] {
            List(_) | LargeList(_) | FixedSizeList(_, _) => Utf8,
            _ => {
                return plan_err!("The array_to_string function can only accept List/LargeList/FixedSizeList.");
            }
        })
    }

    fn invoke(&self, args: &[ColumnarValue]) -> datafusion_common::Result<ColumnarValue> {
        let args = ColumnarValue::values_to_arrays(args)?;
        crate::kernels::array_to_string(&args).map(ColumnarValue::Array)
    }

    fn aliases(&self) -> &[String] {
        &self.aliases
    }
}