Added cast to months_days_ns (#900)

src/compute/cast/mod.rs

@@ -290,6 +290,7 @@ pub fn can_cast_types(from_type: &DataType, to_type: &DataType) -> bool {
         (Timestamp(_, _), Date64) => true,
         (Int64, Duration(_)) => true,
         (Duration(_), Int64) => true,
+        (Interval(_), Interval(IntervalUnit::MonthDayNano)) => true,
         (_, _) => false,
     }
 }
@@ -842,6 +843,13 @@ pub fn cast(array: &dyn Array, to_type: &DataType, options: CastOptions) -> Resu
         (Int64, Duration(_)) => primitive_to_same_primitive_dyn::<i64>(array, to_type),
         (Duration(_), Int64) => primitive_to_same_primitive_dyn::<i64>(array, to_type),
 
+        (Interval(IntervalUnit::DayTime), Interval(IntervalUnit::MonthDayNano)) => {
+            primitive_dyn!(array, days_ms_to_months_days_ns)
+        }
+        (Interval(IntervalUnit::YearMonth), Interval(IntervalUnit::MonthDayNano)) => {
+            primitive_dyn!(array, months_to_months_days_ns)
+        }
+
         (_, _) => Err(ArrowError::NotYetImplemented(format!(
             "Casting from {:?} to {:?} not supported",
             from_type, to_type,

src/compute/cast/primitive_to.rs

@@ -2,7 +2,9 @@ use std::hash::Hash;
 
 use num_traits::{AsPrimitive, Float, ToPrimitive};
 
+use crate::datatypes::IntervalUnit;
 use crate::error::Result;
+use crate::types::{days_ms, months_days_ns};
 use crate::{
     array::*,
     bitmap::Bitmap,
@@ -551,3 +553,31 @@ pub fn naive_timestamp_to_utf8<O: Offset>(
         }
     }
 }
+
+#[inline]
+fn days_ms_to_months_days_ns_scalar(from: days_ms) -> months_days_ns {
+    months_days_ns::new(0, from.days(), from.milliseconds() as i64 * 1000)
+}
+
+/// Casts [`days_ms`]s to [`months_days_ns`]. This operation is infalible and lossless.
+pub fn days_ms_to_months_days_ns(from: &PrimitiveArray<days_ms>) -> PrimitiveArray<months_days_ns> {
+    unary(
+        from,
+        days_ms_to_months_days_ns_scalar,
+        DataType::Interval(IntervalUnit::MonthDayNano),
+    )
+}
+
+#[inline]
+fn months_to_months_days_ns_scalar(from: i32) -> months_days_ns {
+    months_days_ns::new(from, 0, 0)
+}
+
+/// Casts months represented as [`i32`]s to [`months_days_ns`]. This operation is infalible and lossless.
+pub fn months_to_months_days_ns(from: &PrimitiveArray<i32>) -> PrimitiveArray<months_days_ns> {
+    unary(
+        from,
+        months_to_months_days_ns_scalar,
+        DataType::Interval(IntervalUnit::MonthDayNano),
+    )
+}

tests/it/compute/cast.rs

@@ -1,7 +1,7 @@
 use arrow2::array::*;
 use arrow2::compute::cast::{can_cast_types, cast, CastOptions};
 use arrow2::datatypes::*;
-use arrow2::types::NativeType;
+use arrow2::types::{days_ms, months_days_ns, NativeType};
 
 #[test]
 fn i32_to_f64() {
@@ -512,6 +512,29 @@ fn date32_to_date64() {
     );
 }
 
+#[test]
+fn days_ms_to_months_days_ns() {
+    test_primitive_to_primitive(
+        &[days_ms::new(1, 1), days_ms::new(1, 2)],
+        DataType::Interval(IntervalUnit::DayTime),
+        &[
+            months_days_ns::new(0, 1, 1000),
+            months_days_ns::new(0, 1, 2000),
+        ],
+        DataType::Interval(IntervalUnit::MonthDayNano),
+    );
+}
+
+#[test]
+fn months_to_months_days_ns() {
+    test_primitive_to_primitive(
+        &[1, 2],
+        DataType::Interval(IntervalUnit::YearMonth),
+        &[months_days_ns::new(1, 0, 0), months_days_ns::new(2, 0, 0)],
+        DataType::Interval(IntervalUnit::MonthDayNano),
+    );
+}
+
 #[test]
 fn date64_to_date32() {
     test_primitive_to_primitive(