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 = r#"current_date()
39    (optional) SET datafusion.execution.time_zone = '+00:00';
40    SELECT current_date();"#,
41    sql_example = r#"```sql
42> SELECT current_date();
43+----------------+
44| current_date() |
45+----------------+
46| 2024-12-23     |
47+----------------+
48
49-- The current date is based on the session time zone (UTC by default)
50> SET datafusion.execution.time_zone = 'Asia/Tokyo';
51> SELECT current_date();
52+----------------+
53| current_date() |
54+----------------+
55| 2024-12-24     |
56+----------------+
57```"#
58)]
59#[derive(Debug, PartialEq, Eq, Hash)]
60pub struct CurrentDateFunc {
61    signature: Signature,
62    aliases: Vec<String>,
63}
64
65impl Default for CurrentDateFunc {
66    fn default() -> Self {
67        Self::new()
68    }
69}
70
71impl CurrentDateFunc {
72    pub fn new() -> Self {
73        Self {
74            signature: Signature::nullary(Volatility::Stable),
75            aliases: vec![String::from("today")],
76        }
77    }
78}
79
80/// Create an implementation of `current_date()` that always returns the
81/// specified current date.
82///
83/// The semantics of `current_date()` require it to return the same value
84/// wherever it appears within a single statement. This value is
85/// chosen during planning time.
86impl ScalarUDFImpl for CurrentDateFunc {
87    fn name(&self) -> &str {
88        "current_date"
89    }
90
91    fn signature(&self) -> &Signature {
92        &self.signature
93    }
94
95    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
96        Ok(Date32)
97    }
98
99    fn invoke_with_args(&self, _args: ScalarFunctionArgs) -> Result<ColumnarValue> {
100        internal_err!(
101            "invoke should not be called on a simplified current_date() function"
102        )
103    }
104
105    fn aliases(&self) -> &[String] {
106        &self.aliases
107    }
108
109    fn simplify(
110        &self,
111        args: Vec<Expr>,
112        info: &SimplifyContext,
113    ) -> Result<ExprSimplifyResult> {
114        let Some(now_ts) = info.query_execution_start_time() else {
115            return Ok(ExprSimplifyResult::Original(args));
116        };
117
118        // Get timezone from config and convert to local time
119        let days = info
120            .config_options()
121            .execution
122            .time_zone
123            .as_ref()
124            .and_then(|tz| tz.parse::<Tz>().ok())
125            .map_or_else(
126                || datetime_to_days(&now_ts),
127                |tz| {
128                    let local_now = tz.from_utc_datetime(&now_ts.naive_utc());
129                    datetime_to_days(&local_now)
130                },
131            );
132        Ok(ExprSimplifyResult::Simplified(Expr::Literal(
133            ScalarValue::Date32(Some(days)),
134            None,
135        )))
136    }
137
138    fn documentation(&self) -> Option<&Documentation> {
139        self.doc()
140    }
141}
142
143/// Converts a DateTime to the number of days since Unix epoch (1970-01-01)
144fn datetime_to_days<T: Datelike>(dt: &T) -> i32 {
145    dt.num_days_from_ce()
146        - NaiveDate::from_ymd_opt(1970, 1, 1)
147            .unwrap()
148            .num_days_from_ce()
149}
datafusion_functions/datetime/current_date.rs

datafusion_functions/datetime/
current_date.rs
