feat: Implement Spark-compatible CAST from string to timestamp types

core/src/execution/datafusion/expressions/cast.rs

@@ -25,6 +25,7 @@ use std::{
 use crate::errors::{CometError, CometResult};
 use arrow::{
     compute::{cast_with_options, CastOptions},
+    datatypes::TimestampMicrosecondType,
     record_batch::RecordBatch,
     util::display::FormatOptions,
 };
@@ -33,10 +34,12 @@ use arrow_array::{
     Array, ArrayRef, BooleanArray, GenericStringArray, OffsetSizeTrait, PrimitiveArray,
 };
 use arrow_schema::{DataType, Schema};
+use chrono::{TimeZone, Timelike};
 use datafusion::logical_expr::ColumnarValue;
 use datafusion_common::{internal_err, Result as DataFusionResult, ScalarValue};
 use datafusion_physical_expr::PhysicalExpr;
 use num::{traits::CheckedNeg, CheckedSub, Integer, Num};
+use regex::Regex;
 
 use crate::execution::datafusion::expressions::utils::{
     array_with_timezone, down_cast_any_ref, spark_cast,
@@ -86,6 +89,24 @@ macro_rules! cast_utf8_to_int {
     }};
 }
 
+macro_rules! cast_utf8_to_timestamp {
+    ($array:expr, $eval_mode:expr, $array_type:ty, $cast_method:ident) => {{
+        let len = $array.len();
+        let mut cast_array = PrimitiveArray::<$array_type>::builder(len).with_timezone("UTC");
+        for i in 0..len {
+            if $array.is_null(i) {
+                cast_array.append_null()
+            } else if let Ok(Some(cast_value)) = $cast_method($array.value(i).trim(), $eval_mode) {
+                cast_array.append_value(cast_value);
+            } else {
+                cast_array.append_null()
+            }
+        }
+        let result: CometResult<ArrayRef> = Ok(Arc::new(cast_array.finish()) as ArrayRef);
+        result.unwrap()
+    }};
+}
+
 impl Cast {
     pub fn new(
         child: Arc<dyn PhysicalExpr>,
@@ -125,6 +146,9 @@ impl Cast {
             (DataType::LargeUtf8, DataType::Boolean) => {
                 Self::spark_cast_utf8_to_boolean::<i64>(&array, self.eval_mode)?
             }
+            (DataType::Utf8, DataType::Timestamp(_, _)) => {
+                Self::cast_string_to_timestamp(&array, to_type, self.eval_mode)?
+            }
             (
                 DataType::Utf8,
                 DataType::Int8 | DataType::Int16 | DataType::Int32 | DataType::Int64,
@@ -200,6 +224,30 @@ impl Cast {
         Ok(cast_array)
     }
 
+    fn cast_string_to_timestamp(
+        array: &ArrayRef,
+        to_type: &DataType,
+        eval_mode: EvalMode,
+    ) -> CometResult<ArrayRef> {
+        let string_array = array
+            .as_any()
+            .downcast_ref::<GenericStringArray<i32>>()
+            .expect("Expected a string array");
+
+        let cast_array: ArrayRef = match to_type {
+            DataType::Timestamp(_, _) => {
+                cast_utf8_to_timestamp!(
+                    string_array,
+                    eval_mode,
+                    TimestampMicrosecondType,
+                    timestamp_parser
+                )
+            }
+            _ => unreachable!("Invalid data type {:?} in cast from string", to_type),
+        };
+        Ok(cast_array)
+    }
+
     fn spark_cast_utf8_to_boolean<OffsetSize>(
         from: &dyn Array,
         eval_mode: EvalMode,
@@ -510,9 +558,246 @@ impl PhysicalExpr for Cast {
     }
 }
 
+fn timestamp_parser(value: &str, eval_mode: EvalMode) -> CometResult<Option<i64>> {
+    let value = value.trim();
+    if value.is_empty() {
+        return Ok(None);
+    }
+
+    // Define regex patterns and corresponding parsing functions
+    let patterns = &[
+        (
+            Regex::new(r"^\d{4}$").unwrap(),
+            parse_str_to_year_timestamp as fn(&str) -> CometResult<Option<i64>>,
+        ),
+        (
+            Regex::new(r"^\d{4}-\d{2}$").unwrap(),
+            parse_str_to_month_timestamp,
+        ),
+        (
+            Regex::new(r"^\d{4}-\d{2}-\d{2}$").unwrap(),
+            parse_str_to_day_timestamp,
+        ),
+        (
+            Regex::new(r"^\d{4}-\d{2}-\d{2}T\d{1,2}$").unwrap(),
+            parse_str_to_hour_timestamp,
+        ),
+        (
+            Regex::new(r"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}$").unwrap(),
+            parse_str_to_minute_timestamp,
+        ),
+        (
+            Regex::new(r"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}$").unwrap(),
+            parse_str_to_second_timestamp,
+        ),
+        (
+            Regex::new(r"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{1,6}$").unwrap(),
+            parse_str_to_microsecond_timestamp,
+        ),
+        (
+            Regex::new(r"^T\d{1,2}$").unwrap(),
+            parse_str_to_time_only_timestamp,
+        ),
+    ];
+
+    let mut timestamp = None;
+
+    // Iterate through patterns and try matching
+    for (pattern, parse_func) in patterns {
+        if pattern.is_match(value) {
+            timestamp = parse_func(value)?;
+            break;
+        }
+    }
+
+    if timestamp.is_none() {
+        if eval_mode == EvalMode::Ansi {
+            return Err(CometError::CastInvalidValue {
+                value: value.to_string(),
+                from_type: "STRING".to_string(),
+                to_type: "TIMESTAMP".to_string(),
+            });
+        } else {
+            return Ok(None);
+        }
+    }
+    Ok(Some(timestamp.unwrap()))
+}
+
+fn parse_ymd_timestamp(year: i32, month: u32, day: u32) -> CometResult<Option<i64>> {
+    let datetime = chrono::Utc
+        .with_ymd_and_hms(year, month, day, 0, 0, 0)
+        .unwrap()
+        .with_timezone(&chrono::Utc);
+    Ok(Some(datetime.timestamp_micros()))
+}
+
+fn parse_hms_timestamp(
+    year: i32,
+    month: u32,
+    day: u32,
+    hour: u32,
+    minute: u32,
+    second: u32,
+    microsecond: u32,
+) -> CometResult<Option<i64>> {
+    let datetime = chrono::Utc
+        .with_ymd_and_hms(year, month, day, hour, minute, second)
+        .unwrap()
+        .with_timezone(&chrono::Utc)
+        .with_nanosecond(microsecond * 1000);
+    Ok(Some(datetime.unwrap().timestamp_micros()))
+}
+
+fn get_timestamp_values(value: &str, timestamp_type: &str) -> CometResult<Option<i64>> {
+    let values: Vec<_> = value
+        .split(|c| c == 'T' || c == '-' || c == ':' || c == '.')
+        .collect();
+    let year = values[0].parse::<i32>().unwrap_or_default();
+    let month = values.get(1).map_or(1, |m| m.parse::<u32>().unwrap_or(1));
+    let day = values.get(2).map_or(1, |d| d.parse::<u32>().unwrap_or(1));
+    let hour = values.get(3).map_or(0, |h| h.parse::<u32>().unwrap_or(0));
+    let minute = values.get(4).map_or(0, |m| m.parse::<u32>().unwrap_or(0));
+    let second = values.get(5).map_or(0, |s| s.parse::<u32>().unwrap_or(0));
+    let microsecond = values.get(6).map_or(0, |ms| ms.parse::<u32>().unwrap_or(0));
+
+    match timestamp_type {
+        "year" => parse_ymd_timestamp(year, 1, 1),
+        "month" => parse_ymd_timestamp(year, month, 1),
+        "day" => parse_ymd_timestamp(year, month, day),
+        "hour" => parse_hms_timestamp(year, month, day, hour, 0, 0, 0),
+        "minute" => parse_hms_timestamp(year, month, day, hour, minute, 0, 0),
+        "second" => parse_hms_timestamp(year, month, day, hour, minute, second, 0),
+        "microsecond" => parse_hms_timestamp(year, month, day, hour, minute, second, microsecond),
+        _ => Err(CometError::CastInvalidValue {
+            value: value.to_string(),
+            from_type: "STRING".to_string(),
+            to_type: "TIMESTAMP".to_string(),
+        }),
+    }
+}
+
+fn parse_str_to_year_timestamp(value: &str) -> CometResult<Option<i64>> {
+    get_timestamp_values(value, "year")
+}
+
+fn parse_str_to_month_timestamp(value: &str) -> CometResult<Option<i64>> {
+    get_timestamp_values(value, "month")
+}
+
+fn parse_str_to_day_timestamp(value: &str) -> CometResult<Option<i64>> {
+    get_timestamp_values(value, "day")
+}
+
+fn parse_str_to_hour_timestamp(value: &str) -> CometResult<Option<i64>> {
+    get_timestamp_values(value, "hour")
+}
+
+fn parse_str_to_minute_timestamp(value: &str) -> CometResult<Option<i64>> {
+    get_timestamp_values(value, "minute")
+}
+
+fn parse_str_to_second_timestamp(value: &str) -> CometResult<Option<i64>> {
+    get_timestamp_values(value, "second")
+}
+
+fn parse_str_to_microsecond_timestamp(value: &str) -> CometResult<Option<i64>> {
+    get_timestamp_values(value, "microsecond")
+}
+
+fn parse_str_to_time_only_timestamp(value: &str) -> CometResult<Option<i64>> {
+    let values: Vec<&str> = value.split('T').collect();
+    let time_values: Vec<u32> = values[1]
+        .split(':')
+        .map(|v| v.parse::<u32>().unwrap_or(0))
+        .collect();
+
+    let datetime = chrono::Utc::now();
+    let timestamp = datetime
+        .with_hour(time_values.first().copied().unwrap_or_default())
+        .unwrap()
+        .with_minute(*time_values.get(1).unwrap_or(&0))
+        .unwrap()
+        .with_second(*time_values.get(2).unwrap_or(&0))
+        .unwrap()
+        .with_nanosecond(*time_values.get(3).unwrap_or(&0) * 1_000)
+        .unwrap()
+        .to_utc()
+        .timestamp_micros();
+
+    Ok(Some(timestamp))
+}
+
 #[cfg(test)]
-mod test {
-    use super::{cast_string_to_i8, EvalMode};
+mod tests {
+    use super::*;
+    use arrow::datatypes::TimestampMicrosecondType;
+    use arrow_array::StringArray;
+    use arrow_schema::TimeUnit;
+
+    #[test]
+    fn timestamp_parser_test() {
+        // write for all formats
+        assert_eq!(
+            timestamp_parser("2020", EvalMode::Legacy).unwrap(),
+            Some(1577836800000000) // this is in milliseconds
+        );
+        assert_eq!(
+            timestamp_parser("2020-01", EvalMode::Legacy).unwrap(),
+            Some(1577836800000000)
+        );
+        assert_eq!(
+            timestamp_parser("2020-01-01", EvalMode::Legacy).unwrap(),
+            Some(1577836800000000)
+        );
+        assert_eq!(
+            timestamp_parser("2020-01-01T12", EvalMode::Legacy).unwrap(),
+            Some(1577880000000000)
+        );
+        assert_eq!(
+            timestamp_parser("2020-01-01T12:34", EvalMode::Legacy).unwrap(),
+            Some(1577882040000000)
+        );
+        assert_eq!(
+            timestamp_parser("2020-01-01T12:34:56", EvalMode::Legacy).unwrap(),
+            Some(1577882096000000)
+        );
+        assert_eq!(
+            timestamp_parser("2020-01-01T12:34:56.123456", EvalMode::Legacy).unwrap(),
+            Some(1577882096123456)
+        );
+        // assert_eq!(
+        //     timestamp_parser("T2",  EvalMode::Legacy).unwrap(),
+        //     Some(1714356000000000) // this value needs to change everyday.
+        // );
+    }
+
+    #[test]
+    fn test_cast_string_to_timestamp() {
+        let array: ArrayRef = Arc::new(StringArray::from(vec![
+            Some("2020-01-01T12:34:56.123456"),
+            Some("T2"),
+        ]));
+
+        let string_array = array
+            .as_any()
+            .downcast_ref::<GenericStringArray<i32>>()
+            .expect("Expected a string array");
+
+        let eval_mode = EvalMode::Legacy;
+        let result = cast_utf8_to_timestamp!(
+            &string_array,
+            eval_mode,
+            TimestampMicrosecondType,
+            timestamp_parser
+        );
+
+        assert_eq!(
+            result.data_type(),
+            &DataType::Timestamp(TimeUnit::Microsecond, Some("UTC".into()))
+        );
+        assert_eq!(result.len(), 2);
+    }
 
     #[test]
     fn test_cast_string_as_i8() {

spark/src/main/scala/org/apache/comet/serde/QueryPlanSerde.scala

@@ -593,7 +593,13 @@ object QueryPlanSerde extends Logging with ShimQueryPlanSerde {
                 false
               case _ => true
             }
+
             if (supportedCast) {
+              // if Timezone is not UTC, we fallback to Spark
+              if (!timeZoneId.contains("UTC")) {
+                withInfo(expr, s"Unsupported timezone ${timeZoneId} for timestamp cast")
+                None
+              }
               castToProto(timeZoneId, dt, childExpr, evalModeStr)
             } else {
               // no need to call withInfo here since it was called when determining