add test

Author: jonathanc-n

crates/iceberg/src/transform/bucket.rs

@@ -171,12 +171,12 @@ impl TransformFunction for Bucket {
                 .as_any()
                 .downcast_ref::<arrow_array::Time64NanosecondArray>()
                 .unwrap()
-                .unary(|v| self.bucket_time(v)),
+                .unary(|v| self.bucket_time(v / 1000)),
             DataType::Timestamp(TimeUnit::Nanosecond, _) => input
                 .as_any()
                 .downcast_ref::<arrow_array::TimestampNanosecondArray>()
                 .unwrap()
-                .unary(|v| self.bucket_timestamp(v)),
+                .unary(|v| self.bucket_timestamp(v / 1000)),
             DataType::Utf8 => arrow_array::Int32Array::from_iter(
                 input
                     .as_any()
@@ -263,6 +263,9 @@ impl TransformFunction for Bucket {
 
 #[cfg(test)]
 mod test {
+    use std::sync::Arc;
+
+    use arrow_array::{ArrayRef, Int32Array, TimestampMicrosecondArray, TimestampNanosecondArray};
     use chrono::{DateTime, NaiveDate, NaiveDateTime, NaiveTime};
 
     use super::Bucket;
@@ -939,4 +942,28 @@ mod test {
             Datum::int(79)
         );
     }
+
+    #[test]
+    fn test_transform_timestamp_nanos_and_micros_array_equivalence() {
+        let bucket = Bucket::new(100);
+        let micros_value = 1510871468000000;
+        let nanos_value = micros_value * 1000;
+
+        let micro_array = TimestampMicrosecondArray::from_iter_values(vec![micros_value]);
+        let nano_array = TimestampNanosecondArray::from_iter_values(vec![nanos_value]);
+
+        let transformed_micro: ArrayRef = bucket.transform(Arc::new(micro_array)).unwrap();
+        let transformed_nano: ArrayRef = bucket.transform(Arc::new(nano_array)).unwrap();
+
+        let micro_result = transformed_micro
+            .as_any()
+            .downcast_ref::<Int32Array>()
+            .unwrap();
+        let nano_result = transformed_nano
+            .as_any()
+            .downcast_ref::<Int32Array>()
+            .unwrap();
+
+        assert_eq!(micro_result.value(0), nano_result.value(0));
+    }
 }