doc-gen: migrate scalar functions (datetime) documentation 1/2 (#13920)

* doc-gen: migrate scalar functions (datetime) documentation 1/2

* fix: fix typo and update function docs

---------

Co-authored-by: Cheng-Yuan-Lai <a186235@g,ail.com>

datafusion/functions/src/datetime/current_date.rs

@@ -22,13 +22,21 @@ use arrow::datatypes::DataType::Date32;
 use chrono::{Datelike, NaiveDate};
 
 use datafusion_common::{internal_err, Result, ScalarValue};
-use datafusion_expr::scalar_doc_sections::DOC_SECTION_DATETIME;
 use datafusion_expr::simplify::{ExprSimplifyResult, SimplifyInfo};
 use datafusion_expr::{
     ColumnarValue, Documentation, Expr, ScalarUDFImpl, Signature, Volatility,
 };
-use std::sync::OnceLock;
+use datafusion_macros::user_doc;
 
+#[user_doc(
+    doc_section(label = "Time and Date Functions"),
+    description = r#"
+Returns the current UTC date.
+
+The `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.
+"#,
+    syntax_example = "current_date()"
+)]
 #[derive(Debug)]
 pub struct CurrentDateFunc {
     signature: Signature,
@@ -105,22 +113,6 @@ impl ScalarUDFImpl for CurrentDateFunc {
     }
 
     fn documentation(&self) -> Option<&Documentation> {
-        Some(get_current_date_doc())
+        self.doc()
     }
 }
-
-static DOCUMENTATION: OnceLock<Documentation> = OnceLock::new();
-
-fn get_current_date_doc() -> &'static Documentation {
-    DOCUMENTATION.get_or_init(|| {
-        Documentation::builder(
-            DOC_SECTION_DATETIME,
-            r#"
-Returns the current UTC date.
-
-The `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.
-"#,
-            "current_date()")
-            .build()
-    })
-}

datafusion/functions/src/datetime/current_time.rs

@@ -19,15 +19,23 @@ use arrow::datatypes::DataType;
 use arrow::datatypes::DataType::Time64;
 use arrow::datatypes::TimeUnit::Nanosecond;
 use std::any::Any;
-use std::sync::OnceLock;
 
 use datafusion_common::{internal_err, Result, ScalarValue};
-use datafusion_expr::scalar_doc_sections::DOC_SECTION_DATETIME;
 use datafusion_expr::simplify::{ExprSimplifyResult, SimplifyInfo};
 use datafusion_expr::{
     ColumnarValue, Documentation, Expr, ScalarUDFImpl, Signature, Volatility,
 };
+use datafusion_macros::user_doc;
 
+#[user_doc(
+    doc_section(label = "Time and Date Functions"),
+    description = r#"
+Returns the current UTC time.
+
+The `current_time()` return value is determined at query time and will return the same time, no matter when in the query plan the function executes.
+"#,
+    syntax_example = "current_time()"
+)]
 #[derive(Debug)]
 pub struct CurrentTimeFunc {
     signature: Signature,
@@ -93,22 +101,6 @@ impl ScalarUDFImpl for CurrentTimeFunc {
     }
 
     fn documentation(&self) -> Option<&Documentation> {
-        Some(get_current_time_doc())
+        self.doc()
     }
 }
-
-static DOCUMENTATION: OnceLock<Documentation> = OnceLock::new();
-
-fn get_current_time_doc() -> &'static Documentation {
-    DOCUMENTATION.get_or_init(|| {
-        Documentation::builder(
-            DOC_SECTION_DATETIME,
-            r#"
-Returns the current UTC time.
-
-The `current_time()` return value is determined at query time and will return the same time, no matter when in the query plan the function executes.
-"#,
-            "current_time()")
-            .build()
-    })
-}

datafusion/functions/src/datetime/date_bin.rs

@@ -16,7 +16,7 @@
 // under the License.
 
 use std::any::Any;
-use std::sync::{Arc, OnceLock};
+use std::sync::Arc;
 
 use arrow::array::temporal_conversions::NANOSECONDS;
 use arrow::array::types::{
@@ -37,10 +37,64 @@ use datafusion_expr::TypeSignature::Exact;
 use datafusion_expr::{
     ColumnarValue, Documentation, ScalarUDFImpl, Signature, Volatility, TIMEZONE_WILDCARD,
 };
+use datafusion_macros::user_doc;
 
 use chrono::{DateTime, Datelike, Duration, Months, TimeDelta, Utc};
-use datafusion_expr::scalar_doc_sections::DOC_SECTION_DATETIME;
 
+#[user_doc(
+    doc_section(label = "Time and Date Functions"),
+    description = r#"
+Calculates time intervals and returns the start of the interval nearest to the specified timestamp. Use `date_bin` to downsample time series data by grouping rows into time-based "bins" or "windows" and applying an aggregate or selector function to each window.
+
+For example, if you "bin" or "window" data into 15 minute intervals, an input timestamp of `2023-01-01T18:18:18Z` will be updated to the start time of the 15 minute bin it is in: `2023-01-01T18:15:00Z`.
+"#,
+    syntax_example = "date_bin(interval, expression, origin-timestamp)",
+    sql_example = r#"```sql
+-- Bin the timestamp into 1 day intervals
+> SELECT date_bin(interval '1 day', time) as bin
+FROM VALUES ('2023-01-01T18:18:18Z'), ('2023-01-03T19:00:03Z')  t(time);
++---------------------+
+| bin                 |
++---------------------+
+| 2023-01-01T00:00:00 |
+| 2023-01-03T00:00:00 |
++---------------------+
+2 row(s) fetched.
+
+-- Bin the timestamp into 1 day intervals starting at 3AM on  2023-01-01
+> SELECT date_bin(interval '1 day', time,  '2023-01-01T03:00:00') as bin
+FROM VALUES ('2023-01-01T18:18:18Z'), ('2023-01-03T19:00:03Z')  t(time);
++---------------------+
+| bin                 |
++---------------------+
+| 2023-01-01T03:00:00 |
+| 2023-01-03T03:00:00 |
++---------------------+
+2 row(s) fetched.
+```"#,
+    argument(name = "interval", description = "Bin interval."),
+    argument(
+        name = "expression",
+        description = "Time expression to operate on. Can be a constant, column, or function."
+    ),
+    argument(
+        name = "origin-timestamp",
+        description = r#"Optional. Starting point used to determine bin boundaries. If not specified defaults 1970-01-01T00:00:00Z (the UNIX epoch in UTC). The following intervals are supported:
+
+    - nanoseconds
+    - microseconds
+    - milliseconds
+    - seconds
+    - minutes
+    - hours
+    - days
+    - weeks
+    - months
+    - years
+    - century
+"#
+    )
+)]
 #[derive(Debug)]
 pub struct DateBinFunc {
     signature: Signature,
@@ -169,68 +223,10 @@ impl ScalarUDFImpl for DateBinFunc {
         }
     }
     fn documentation(&self) -> Option<&Documentation> {
-        Some(get_date_bin_doc())
+        self.doc()
     }
 }
 
-static DOCUMENTATION: OnceLock<Documentation> = OnceLock::new();
-
-fn get_date_bin_doc() -> &'static Documentation {
-    DOCUMENTATION.get_or_init(|| {
-        Documentation::builder(
-            DOC_SECTION_DATETIME,
-            r#"
-Calculates time intervals and returns the start of the interval nearest to the specified timestamp. Use `date_bin` to downsample time series data by grouping rows into time-based "bins" or "windows" and applying an aggregate or selector function to each window.
-
-For example, if you "bin" or "window" data into 15 minute intervals, an input timestamp of `2023-01-01T18:18:18Z` will be updated to the start time of the 15 minute bin it is in: `2023-01-01T18:15:00Z`.
-"#,
-            "date_bin(interval, expression, origin-timestamp)")
-            .with_sql_example(r#"```sql
--- Bin the timestamp into 1 day intervals
-> SELECT date_bin(interval '1 day', time) as bin
-FROM VALUES ('2023-01-01T18:18:18Z'), ('2023-01-03T19:00:03Z')  t(time);
-+---------------------+
-| bin                 |
-+---------------------+
-| 2023-01-01T00:00:00 |
-| 2023-01-03T00:00:00 |
-+---------------------+
-2 row(s) fetched.
-
--- Bin the timestamp into 1 day intervals starting at 3AM on  2023-01-01
-> SELECT date_bin(interval '1 day', time,  '2023-01-01T03:00:00') as bin
-FROM VALUES ('2023-01-01T18:18:18Z'), ('2023-01-03T19:00:03Z')  t(time);
-+---------------------+
-| bin                 |
-+---------------------+
-| 2023-01-01T03:00:00 |
-| 2023-01-03T03:00:00 |
-+---------------------+
-2 row(s) fetched.
-```
-"#)
-            .with_argument("interval", "Bin interval.")
-            .with_argument("expression", "Time expression to operate on. Can be a constant, column, or function.")
-            .with_argument("origin-timestamp", "Optional. Starting point used to determine bin boundaries. If not specified defaults 1970-01-01T00:00:00Z (the UNIX epoch in UTC).
-
-The following intervals are supported:
-
-- nanoseconds
-- microseconds
-- milliseconds
-- seconds
-- minutes
-- hours
-- days
-- weeks
-- months
-- years
-- century
-")
-            .build()
-    })
-}
-
 enum Interval {
     Nanoseconds(i64),
     Months(i64),

datafusion/functions/src/datetime/date_part.rs

@@ -17,7 +17,7 @@
 
 use std::any::Any;
 use std::str::FromStr;
-use std::sync::{Arc, OnceLock};
+use std::sync::Arc;
 
 use arrow::array::{Array, ArrayRef, Float64Array, Int32Array};
 use arrow::compute::kernels::cast_utils::IntervalUnit;
@@ -41,11 +41,42 @@ use datafusion_common::{
     ExprSchema, Result, ScalarValue,
 };
 use datafusion_expr::{
-    scalar_doc_sections::DOC_SECTION_DATETIME, ColumnarValue, Documentation, Expr,
-    ScalarUDFImpl, Signature, TypeSignature, Volatility,
+    ColumnarValue, Documentation, Expr, ScalarUDFImpl, Signature, TypeSignature,
+    Volatility,
 };
 use datafusion_expr_common::signature::TypeSignatureClass;
-
+use datafusion_macros::user_doc;
+
+#[user_doc(
+    doc_section(label = "Time and Date Functions"),
+    description = "Returns the specified part of the date as an integer.",
+    syntax_example = "date_part(part, expression)",
+    alternative_syntax = "extract(field FROM source)",
+    argument(
+        name = "part",
+        description = r#"Part of the date to return. The following date parts are supported:
+        
+    - year
+    - quarter (emits value in inclusive range [1, 4] based on which quartile of the year the date is in)
+    - month
+    - week (week of the year)
+    - day (day of the month)
+    - hour
+    - minute
+    - second
+    - millisecond
+    - microsecond
+    - nanosecond
+    - dow (day of the week)
+    - doy (day of the year)
+    - epoch (seconds since Unix epoch)
+"#
+    ),
+    argument(
+        name = "expression",
+        description = "Time expression to operate on. Can be a constant, column, or function."
+    )
+)]
 #[derive(Debug)]
 pub struct DatePartFunc {
     signature: Signature,
@@ -190,7 +221,7 @@ impl ScalarUDFImpl for DatePartFunc {
         &self.aliases
     }
     fn documentation(&self) -> Option<&Documentation> {
-        Some(get_date_part_doc())
+        self.doc()
     }
 }
 
@@ -206,43 +237,6 @@ fn part_normalization(part: &str) -> &str {
         .unwrap_or(part)
 }
 
-static DOCUMENTATION: OnceLock<Documentation> = OnceLock::new();
-
-fn get_date_part_doc() -> &'static Documentation {
-    DOCUMENTATION.get_or_init(|| {
-        Documentation::builder(
-            DOC_SECTION_DATETIME,
-            "Returns the specified part of the date as an integer.",
-            "date_part(part, expression)")
-            .with_argument(
-                "part",
-                r#"Part of the date to return. The following date parts are supported:
-
-    - year
-    - quarter (emits value in inclusive range [1, 4] based on which quartile of the year the date is in)
-    - month
-    - week (week of the year)
-    - day (day of the month)
-    - hour
-    - minute
-    - second
-    - millisecond
-    - microsecond
-    - nanosecond
-    - dow (day of the week)
-    - doy (day of the year)
-    - epoch (seconds since Unix epoch)
-"#,
-            )
-            .with_argument(
-                "expression",
-                "Time expression to operate on. Can be a constant, column, or function.",
-            )
-            .with_alternative_syntax("extract(field FROM source)")
-            .build()
-    })
-}
-
 /// Invoke [`date_part`] on an `array` (e.g. Timestamp) and convert the
 /// result to a total number of seconds, milliseconds, microseconds or
 /// nanoseconds