datafusion_functions/datetime/
current_date.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 arrow::array::timezone::Tz;
19use arrow::datatypes::DataType;
20use arrow::datatypes::DataType::Date32;
21use chrono::{Datelike, NaiveDate, TimeZone};
22
23use datafusion_common::{Result, ScalarValue, internal_err};
24use datafusion_expr::simplify::{ExprSimplifyResult, SimplifyContext};
25use datafusion_expr::{
26    ColumnarValue, Documentation, Expr, ScalarFunctionArgs, ScalarUDFImpl, Signature,
27    Volatility,
28};
29use datafusion_macros::user_doc;
30
31#[user_doc(
32    doc_section(label = "Time and Date Functions"),
33    description = r#"
34Returns the current date in the session time zone.
35
36The `current_date()` return value is determined at query time and will return the same date, no matter when in the query plan the function executes.
37"#,
38    syntax_example = "current_date()",
39    sql_example = r#"```sql
40> SELECT current_date();
41+----------------+
42| current_date() |
43+----------------+
44| 2024-12-23     |
45+----------------+
46
47-- The current date is based on the session time zone (UTC by default)
48> SET datafusion.execution.time_zone = 'Asia/Tokyo';
49> SELECT current_date();
50+----------------+
51| current_date() |
52+----------------+
53| 2024-12-24     |
54+----------------+
55```"#
56)]
57#[derive(Debug, PartialEq, Eq, Hash)]
58pub struct CurrentDateFunc {
59    signature: Signature,
60    aliases: Vec<String>,
61}
62
63impl Default for CurrentDateFunc {
64    fn default() -> Self {
65        Self::new()
66    }
67}
68
69impl CurrentDateFunc {
70    pub fn new() -> Self {
71        Self {
72            signature: Signature::nullary(Volatility::Stable),
73            aliases: vec![String::from("today")],
74        }
75    }
76}
77
78/// Create an implementation of `current_date()` that always returns the
79/// specified current date.
80///
81/// The semantics of `current_date()` require it to return the same value
82/// wherever it appears within a single statement. This value is
83/// chosen during planning time.
84impl ScalarUDFImpl for CurrentDateFunc {
85    fn name(&self) -> &str {
86        "current_date"
87    }
88
89    fn signature(&self) -> &Signature {
90        &self.signature
91    }
92
93    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
94        Ok(Date32)
95    }
96
97    fn invoke_with_args(&self, _args: ScalarFunctionArgs) -> Result<ColumnarValue> {
98        internal_err!(
99            "invoke should not be called on a simplified current_date() function"
100        )
101    }
102
103    fn aliases(&self) -> &[String] {
104        &self.aliases
105    }
106
107    fn simplify(
108        &self,
109        args: Vec<Expr>,
110        info: &SimplifyContext,
111    ) -> Result<ExprSimplifyResult> {
112        let Some(now_ts) = info.query_execution_start_time() else {
113            return Ok(ExprSimplifyResult::Original(args));
114        };
115
116        // Get timezone from config and convert to local time
117        let days = info
118            .config_options()
119            .execution
120            .time_zone
121            .as_ref()
122            .and_then(|tz| tz.parse::<Tz>().ok())
123            .map_or_else(
124                || datetime_to_days(&now_ts),
125                |tz| {
126                    let local_now = tz.from_utc_datetime(&now_ts.naive_utc());
127                    datetime_to_days(&local_now)
128                },
129            );
130        Ok(ExprSimplifyResult::Simplified(Expr::Literal(
131            ScalarValue::Date32(Some(days)),
132            None,
133        )))
134    }
135
136    fn documentation(&self) -> Option<&Documentation> {
137        self.doc()
138    }
139}
140
141/// Converts a DateTime to the number of days since Unix epoch (1970-01-01)
142fn datetime_to_days<T: Datelike>(dt: &T) -> i32 {
143    dt.num_days_from_ce()
144        - NaiveDate::from_ymd_opt(1970, 1, 1)
145            .unwrap()
146            .num_days_from_ce()
147}
datafusion_functions/datetime/current_date.rs

datafusion_functions/datetime/
current_date.rs
