feat: to_time function (#19540)

## Which issue does this PR close?

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- Part of #19025.

## Rationale for this change

Previously we needed to create timestamp and then extract the time
component from that.

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in the issue then this section is not needed.
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## What changes are included in this PR?

- Added the function for `to_time`
- Relevant slt test
- Relevant unit tests
- Updated docs

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## Are these changes tested?

- All tests pass

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## Are there any user-facing changes?

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---------

Co-authored-by: Jeffrey Vo <[email protected]>

Author: kumarUjjawal

datafusion/functions/src/datetime/mod.rs

@@ -35,6 +35,7 @@ pub mod planner;
 pub mod to_char;
 pub mod to_date;
 pub mod to_local_time;
+pub mod to_time;
 pub mod to_timestamp;
 pub mod to_unixtime;
 
@@ -50,6 +51,7 @@ make_udf_function!(from_unixtime::FromUnixtimeFunc, from_unixtime);
 make_udf_function!(to_char::ToCharFunc, to_char);
 make_udf_function!(to_date::ToDateFunc, to_date);
 make_udf_function!(to_local_time::ToLocalTimeFunc, to_local_time);
+make_udf_function!(to_time::ToTimeFunc, to_time);
 make_udf_function!(to_unixtime::ToUnixtimeFunc, to_unixtime);
 make_udf_function!(to_timestamp::ToTimestampFunc, to_timestamp);
 make_udf_function!(to_timestamp::ToTimestampSecondsFunc, to_timestamp_seconds);
@@ -110,6 +112,10 @@ pub mod expr_fn {
         to_unixtime,
         "converts a value to seconds since the unix epoch",
         args,
+    ),(
+        to_time,
+        "converts a string and optional formats to a `Time64(Nanoseconds)`",
+        args,
     ),(
         to_timestamp,
         "converts a string and optional formats to a `Timestamp(Nanoseconds, None)`",
@@ -278,6 +284,7 @@ pub fn functions() -> Vec<Arc<ScalarUDF>> {
         to_char(),
         to_date(),
         to_local_time(),
+        to_time(),
         to_unixtime(),
         to_timestamp(),
         to_timestamp_seconds(),

datafusion/functions/src/datetime/to_time.rs

@@ -0,0 +1,252 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use crate::datetime::common::*;
+use arrow::array::builder::PrimitiveBuilder;
+use arrow::array::cast::AsArray;
+use arrow::array::temporal_conversions::time_to_time64ns;
+use arrow::array::types::Time64NanosecondType;
+use arrow::array::{Array, PrimitiveArray, StringArrayType};
+use arrow::datatypes::DataType;
+use arrow::datatypes::DataType::*;
+use chrono::NaiveTime;
+use datafusion_common::{Result, ScalarValue, exec_err};
+use datafusion_expr::{
+    ColumnarValue, Documentation, ScalarUDFImpl, Signature, Volatility,
+};
+use datafusion_macros::user_doc;
+use std::any::Any;
+use std::sync::Arc;
+
+/// Default time formats to try when parsing without an explicit format
+const DEFAULT_TIME_FORMATS: &[&str] = &[
+    "%H:%M:%S%.f", // 12:30:45.123456789
+    "%H:%M:%S",    // 12:30:45
+    "%H:%M",       // 12:30
+];
+
+#[user_doc(
+    doc_section(label = "Time and Date Functions"),
+    description = r"Converts a value to a time (`HH:MM:SS.nnnnnnnnn`).
+Supports strings and timestamps as input.
+Strings are parsed as `HH:MM:SS`, `HH:MM:SS.nnnnnnnnn`, or `HH:MM` if no [Chrono format](https://docs.rs/chrono/latest/chrono/format/strftime/index.html)s are provided.
+Timestamps will have the time portion extracted.
+Returns the corresponding time.
+
+Note: `to_time` returns Time64(Nanosecond), which represents the time of day in nanoseconds since midnight.",
+    syntax_example = "to_time('12:30:45', '%H:%M:%S')",
+    sql_example = r#"```sql
+> select to_time('12:30:45');
++---------------------------+
+| to_time(Utf8("12:30:45")) |
++---------------------------+
+| 12:30:45                  |
++---------------------------+
+> select to_time('12-30-45', '%H-%M-%S');
++--------------------------------------------+
+| to_time(Utf8("12-30-45"),Utf8("%H-%M-%S")) |
++--------------------------------------------+
+| 12:30:45                                   |
++--------------------------------------------+
+> select to_time('2024-01-15 14:30:45'::timestamp);
++--------------------------------------------------+
+| to_time(Utf8("2024-01-15 14:30:45"))             |
++--------------------------------------------------+
+| 14:30:45                                         |
++--------------------------------------------------+
+```
+
+Additional examples can be found [here](https://github.com/apache/datafusion/blob/main/datafusion-examples/examples/builtin_functions/date_time.rs)
+"#,
+    standard_argument(name = "expression", prefix = "String or Timestamp"),
+    argument(
+        name = "format_n",
+        description = r"Optional [Chrono format](https://docs.rs/chrono/latest/chrono/format/strftime/index.html) strings to use to parse the expression. Formats will be tried in the order
+  they appear with the first successful one being returned. If none of the formats successfully parse the expression
+  an error will be returned."
+    )
+)]
+#[derive(Debug, PartialEq, Eq, Hash)]
+pub struct ToTimeFunc {
+    signature: Signature,
+}
+
+impl Default for ToTimeFunc {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl ToTimeFunc {
+    pub fn new() -> Self {
+        Self {
+            signature: Signature::variadic_any(Volatility::Immutable),
+        }
+    }
+}
+
+impl ScalarUDFImpl for ToTimeFunc {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn name(&self) -> &str {
+        "to_time"
+    }
+
+    fn signature(&self) -> &Signature {
+        &self.signature
+    }
+
+    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
+        Ok(Time64(arrow::datatypes::TimeUnit::Nanosecond))
+    }
+
+    fn invoke_with_args(
+        &self,
+        args: datafusion_expr::ScalarFunctionArgs,
+    ) -> Result<ColumnarValue> {
+        let args = args.args;
+        if args.is_empty() {
+            return exec_err!("to_time function requires 1 or more arguments, got 0");
+        }
+
+        // validate that any args after the first one are Utf8
+        if args.len() > 1 {
+            validate_data_types(&args, "to_time")?;
+        }
+
+        match args[0].data_type() {
+            Utf8View | LargeUtf8 | Utf8 => string_to_time(&args),
+            Null => Ok(ColumnarValue::Scalar(ScalarValue::Time64Nanosecond(None))),
+            // Support timestamp input by extracting time portion using Arrow cast
+            Timestamp(_, _) => timestamp_to_time(&args[0]),
+            other => {
+                exec_err!("Unsupported data type {} for function to_time", other)
+            }
+        }
+    }
+
+    fn documentation(&self) -> Option<&Documentation> {
+        self.doc()
+    }
+}
+
+/// Convert string arguments to time (standalone function, not a method on ToTimeFunc)
+fn string_to_time(args: &[ColumnarValue]) -> Result<ColumnarValue> {
+    let formats = collect_formats(args)?;
+
+    match &args[0] {
+        ColumnarValue::Scalar(ScalarValue::Utf8(s))
+        | ColumnarValue::Scalar(ScalarValue::LargeUtf8(s))
+        | ColumnarValue::Scalar(ScalarValue::Utf8View(s)) => {
+            let result = s
+                .as_ref()
+                .map(|s| parse_time_with_formats(s, &formats))
+                .transpose()?;
+            Ok(ColumnarValue::Scalar(ScalarValue::Time64Nanosecond(result)))
+        }
+        ColumnarValue::Array(array) => {
+            let result = match array.data_type() {
+                Utf8 => parse_time_array(&array.as_string::<i32>(), &formats)?,
+                LargeUtf8 => parse_time_array(&array.as_string::<i64>(), &formats)?,
+                Utf8View => parse_time_array(&array.as_string_view(), &formats)?,
+                other => return exec_err!("Unsupported type for to_time: {other}"),
+            };
+            Ok(ColumnarValue::Array(Arc::new(result)))
+        }
+        other => exec_err!("Unsupported argument for to_time: {other:?}"),
+    }
+}
+
+/// Collect format strings from arguments, erroring on non-scalar inputs
+fn collect_formats(args: &[ColumnarValue]) -> Result<Vec<&str>> {
+    if args.len() <= 1 {
+        return Ok(DEFAULT_TIME_FORMATS.to_vec());
+    }
+
+    let mut formats = Vec::with_capacity(args.len() - 1);
+    for (i, arg) in args[1..].iter().enumerate() {
+        match arg {
+            ColumnarValue::Scalar(ScalarValue::Utf8(Some(s)))
+            | ColumnarValue::Scalar(ScalarValue::LargeUtf8(Some(s)))
+            | ColumnarValue::Scalar(ScalarValue::Utf8View(Some(s))) => {
+                formats.push(s.as_str());
+            }
+            ColumnarValue::Scalar(ScalarValue::Utf8(None))
+            | ColumnarValue::Scalar(ScalarValue::LargeUtf8(None))
+            | ColumnarValue::Scalar(ScalarValue::Utf8View(None)) => {
+                // Skip null format strings
+            }
+            ColumnarValue::Array(_) => {
+                return exec_err!(
+                    "to_time format argument {} must be a scalar, not an array",
+                    i + 2 // argument position (1-indexed, +1 for the first arg)
+                );
+            }
+            other => {
+                return exec_err!(
+                    "to_time format argument {} has unsupported type: {:?}",
+                    i + 2,
+                    other.data_type()
+                );
+            }
+        }
+    }
+    Ok(formats)
+}
+
+/// Extract time portion from timestamp using Arrow cast kernel
+fn timestamp_to_time(arg: &ColumnarValue) -> Result<ColumnarValue> {
+    arg.cast_to(&Time64(arrow::datatypes::TimeUnit::Nanosecond), None)
+}
+
+/// Parse time array using the provided formats
+fn parse_time_array<'a, A: StringArrayType<'a>>(
+    array: &A,
+    formats: &[&str],
+) -> Result<PrimitiveArray<Time64NanosecondType>> {
+    let mut builder: PrimitiveBuilder<Time64NanosecondType> =
+        PrimitiveArray::builder(array.len());
+
+    for i in 0..array.len() {
+        if array.is_null(i) {
+            builder.append_null();
+        } else {
+            let s = array.value(i);
+            let nanos = parse_time_with_formats(s, formats)?;
+            builder.append_value(nanos);
+        }
+    }
+
+    Ok(builder.finish())
+}
+
+/// Parse time string using provided formats
+fn parse_time_with_formats(s: &str, formats: &[&str]) -> Result<i64> {
+    for format in formats {
+        if let Ok(time) = NaiveTime::parse_from_str(s, format) {
+            // Use Arrow's time_to_time64ns function instead of custom implementation
+            return Ok(time_to_time64ns(time));
+        }
+    }
+    exec_err!(
+        "Error parsing '{}' as time. Tried formats: {:?}",
+        s,
+        formats
+    )
+}