From 096ef28dde6b1ae43ce89ba2c3a9d98295f2972e Mon Sep 17 00:00:00 2001
From: Alex Qyoun-ae <4062971+MazterQyou@users.noreply.github.com>
Date: Thu, 15 Dec 2022 21:42:47 +0400
Subject: [PATCH] feat: Support casting `Date32` to `Timestamp`

---
 arrow/src/compute/kernels/cast.rs | 40 +++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/arrow/src/compute/kernels/cast.rs b/arrow/src/compute/kernels/cast.rs
index 2fdc807aa48e..49b7e5741df5 100644
--- a/arrow/src/compute/kernels/cast.rs
+++ b/arrow/src/compute/kernels/cast.rs
@@ -229,6 +229,7 @@ pub fn can_cast_types(from_type: &DataType, to_type: &DataType) -> bool {
         (Timestamp(_, _), Int64) => true,
         (Int64, Timestamp(_, _)) => true,
         (Timestamp(_, _), Timestamp(_, _) | Date32 | Date64) => true,
+        (Date32, Timestamp(_, _)) => true,
         // date64 to timestamp might not make sense,
         (Int64, Duration(_)) => true,
         (Duration(_), Int64) => true,
@@ -1161,6 +1162,32 @@ pub fn cast_with_options(
 
             Ok(Arc::new(b.finish()) as ArrayRef)
         }
+        (Date32, Timestamp(to_unit, _)) => {
+            let time_array = Int32Array::from(array.data().clone());
+            let time_array = numeric_cast::<Int32Type, Int64Type>(&time_array);
+            let to_size = time_unit_multiple(to_unit) * SECONDS_IN_DAY;
+            let converted =
+                multiply(&time_array, &Int64Array::from(vec![to_size; array.len()]))?;
+            let array_ref = Arc::new(converted) as ArrayRef;
+            use TimeUnit::*;
+            match to_unit {
+                Second => {
+                    cast_array_data::<TimestampSecondType>(&array_ref, to_type.clone())
+                }
+                Millisecond => cast_array_data::<TimestampMillisecondType>(
+                    &array_ref,
+                    to_type.clone(),
+                ),
+                Microsecond => cast_array_data::<TimestampMicrosecondType>(
+                    &array_ref,
+                    to_type.clone(),
+                ),
+                Nanosecond => cast_array_data::<TimestampNanosecondType>(
+                    &array_ref,
+                    to_type.clone(),
+                ),
+            }
+        }
         (Timestamp(from_unit, _), Date64) => {
             let from_size = time_unit_multiple(from_unit);
             let to_size = MILLISECONDS;
@@ -2970,6 +2997,19 @@ mod tests {
         assert!(c.is_null(2));
     }
 
+    #[test]
+    fn test_cast_date32_to_timestamp() {
+        let a = Date32Array::from(vec![10000, 17890]);
+        let array = Arc::new(a) as ArrayRef;
+        let b = cast(&array, &DataType::Timestamp(TimeUnit::Nanosecond, None)).unwrap();
+        let c = b
+            .as_any()
+            .downcast_ref::<TimestampNanosecondArray>()
+            .unwrap();
+        assert_eq!(864000000000000000, c.value(0));
+        assert_eq!(1545696000000000000, c.value(1));
+    }
+
     #[test]
     fn test_cast_timestamp_to_date64() {
         let a = TimestampMillisecondArray::from_opt_vec(