datafusion_functions_nested/
max.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
18//! [`ScalarUDFImpl`] definitions for array_max function.
19use crate::utils::make_scalar_function;
20use arrow::array::{ArrayRef, GenericListArray, OffsetSizeTrait};
21use arrow::datatypes::DataType;
22use arrow::datatypes::DataType::{LargeList, List};
23use datafusion_common::cast::{as_large_list_array, as_list_array};
24use datafusion_common::utils::take_function_args;
25use datafusion_common::Result;
26use datafusion_common::{exec_err, plan_err, ScalarValue};
27use datafusion_doc::Documentation;
28use datafusion_expr::{
29    ColumnarValue, ScalarFunctionArgs, ScalarUDFImpl, Signature, Volatility,
30};
31use datafusion_functions_aggregate::min_max;
32use datafusion_macros::user_doc;
33use itertools::Itertools;
34use std::any::Any;
35
36make_udf_expr_and_func!(
37    ArrayMax,
38    array_max,
39    array,
40    "returns the maximum value in the array.",
41    array_max_udf
42);
43
44#[user_doc(
45    doc_section(label = "Array Functions"),
46    description = "Returns the maximum value in the array.",
47    syntax_example = "array_max(array)",
48    sql_example = r#"```sql
49> select array_max([3,1,4,2]);
50+-----------------------------------------+
51| array_max(List([3,1,4,2]))              |
52+-----------------------------------------+
53| 4                                       |
54+-----------------------------------------+
55```"#,
56    argument(
57        name = "array",
58        description = "Array expression. Can be a constant, column, or function, and any combination of array operators."
59    )
60)]
61#[derive(Debug)]
62pub struct ArrayMax {
63    signature: Signature,
64    aliases: Vec<String>,
65}
66
67impl Default for ArrayMax {
68    fn default() -> Self {
69        Self::new()
70    }
71}
72
73impl ArrayMax {
74    pub fn new() -> Self {
75        Self {
76            signature: Signature::array(Volatility::Immutable),
77            aliases: vec!["list_max".to_string()],
78        }
79    }
80}
81
82impl ScalarUDFImpl for ArrayMax {
83    fn as_any(&self) -> &dyn Any {
84        self
85    }
86
87    fn name(&self) -> &str {
88        "array_max"
89    }
90
91    fn signature(&self) -> &Signature {
92        &self.signature
93    }
94
95    fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
96        let [array] = take_function_args(self.name(), arg_types)?;
97        match array {
98            List(field) | LargeList(field) => Ok(field.data_type().clone()),
99            arg_type => plan_err!("{} does not support type {arg_type}", self.name()),
100        }
101    }
102
103    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
104        make_scalar_function(array_max_inner)(&args.args)
105    }
106
107    fn aliases(&self) -> &[String] {
108        &self.aliases
109    }
110
111    fn documentation(&self) -> Option<&Documentation> {
112        self.doc()
113    }
114}
115
116/// array_max SQL function
117///
118/// There is one argument for array_max as the array.
119/// `array_max(array)`
120///
121/// For example:
122/// > array_max(\[1, 3, 2]) -> 3
123pub fn array_max_inner(args: &[ArrayRef]) -> Result<ArrayRef> {
124    let [array] = take_function_args("array_max", args)?;
125    match array.data_type() {
126        List(_) => general_array_max(as_list_array(array)?),
127        LargeList(_) => general_array_max(as_large_list_array(array)?),
128        arg_type => exec_err!("array_max does not support type: {arg_type}"),
129    }
130}
131
132fn general_array_max<O: OffsetSizeTrait>(
133    array: &GenericListArray<O>,
134) -> Result<ArrayRef> {
135    let null_value = ScalarValue::try_from(array.value_type())?;
136    let result_vec: Vec<ScalarValue> = array
137        .iter()
138        .map(|arr| {
139            arr.as_ref()
140                .map_or_else(|| Ok(null_value.clone()), min_max::max_batch)
141        })
142        .try_collect()?;
143    ScalarValue::iter_to_array(result_vec)
144}
datafusion_functions_nested/max.rs

datafusion_functions_nested/
max.rs
