datafusion_spark/function/datetime/
monthname.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::sync::Arc;
19
20use arrow::array::{AsArray, StringArray};
21use arrow::compute::{DatePart, date_part};
22use arrow::datatypes::{DataType, Field, FieldRef};
23use datafusion_common::types::{NativeType, logical_date};
24use datafusion_common::utils::take_function_args;
25use datafusion_common::{Result, ScalarValue, internal_err};
26use datafusion_expr::{
27    Coercion, ColumnarValue, ReturnFieldArgs, ScalarFunctionArgs, ScalarUDFImpl,
28    Signature, TypeSignatureClass, Volatility,
29};
30
31const MONTH_NAMES: [&str; 12] = [
32    "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
33];
34
35fn month_number_to_name(month: i32) -> Option<&'static str> {
36    MONTH_NAMES.get((month - 1) as usize).copied()
37}
38
39/// Spark-compatible `monthname` expression.
40/// Returns the three-letter abbreviated month name from a date or timestamp.
41///
42/// <https://spark.apache.org/docs/latest/api/sql/index.html#monthname>
43#[derive(Debug, PartialEq, Eq, Hash)]
44pub struct SparkMonthName {
45    signature: Signature,
46}
47
48impl Default for SparkMonthName {
49    fn default() -> Self {
50        Self::new()
51    }
52}
53
54impl SparkMonthName {
55    pub fn new() -> Self {
56        Self {
57            signature: Signature::coercible(
58                vec![Coercion::new_implicit(
59                    TypeSignatureClass::Native(logical_date()),
60                    vec![TypeSignatureClass::Timestamp],
61                    NativeType::Date,
62                )],
63                Volatility::Immutable,
64            ),
65        }
66    }
67}
68
69impl ScalarUDFImpl for SparkMonthName {
70    fn name(&self) -> &str {
71        "monthname"
72    }
73
74    fn signature(&self) -> &Signature {
75        &self.signature
76    }
77
78    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
79        internal_err!("return_field_from_args should be used instead")
80    }
81
82    fn return_field_from_args(&self, args: ReturnFieldArgs) -> Result<FieldRef> {
83        let nullable = args.arg_fields.iter().any(|f| f.is_nullable());
84        Ok(Arc::new(Field::new(self.name(), DataType::Utf8, nullable)))
85    }
86
87    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
88        let [arg] = take_function_args(self.name(), args.args)?;
89        match arg {
90            ColumnarValue::Scalar(scalar) => {
91                if scalar.is_null() {
92                    return Ok(ColumnarValue::Scalar(ScalarValue::Utf8(None)));
93                }
94                let arr = scalar.to_array_of_size(1)?;
95                let month_arr = date_part(&arr, DatePart::Month)?;
96                let month_val = month_arr
97                    .as_primitive::<arrow::datatypes::Int32Type>()
98                    .value(0);
99                let name = month_number_to_name(month_val).map(|s| s.to_string());
100                Ok(ColumnarValue::Scalar(ScalarValue::Utf8(name)))
101            }
102            ColumnarValue::Array(arr) => {
103                let month_arr = date_part(&arr, DatePart::Month)?;
104                let int_arr = month_arr.as_primitive::<arrow::datatypes::Int32Type>();
105
106                let result: StringArray = int_arr
107                    .iter()
108                    .map(|maybe_month| maybe_month.and_then(month_number_to_name))
109                    .collect();
110
111                Ok(ColumnarValue::Array(Arc::new(result)))
112            }
113        }
114    }
115}
datafusion_spark/function/datetime/monthname.rs

datafusion_spark/function/datetime/
monthname.rs
