[GitHub] [arrow-rs] liukun4515 commented on a change in pull request #1044: support cast signed numeric to decimal

[GitBox <gi...@apache.org>]

liukun4515 commented on a change in pull request #1044:
URL: https://github.com/apache/arrow-rs/pull/1044#discussion_r771765941



##########
File path: arrow/src/compute/kernels/cast.rs
##########
@@ -1837,6 +1906,125 @@ where
 mod tests {
     use super::*;
     use crate::{buffer::Buffer, util::display::array_value_to_string};
+    use num::traits::Pow;
+
+    #[test]
+    fn test_cast_numeric_to_decimal() {
+        let data_types = vec![
+            DataType::Int8,
+            DataType::Int16,
+            DataType::Int32,
+            DataType::Int64,
+            DataType::Float32,
+            DataType::Float64,
+        ];
+        let decimal_type = DataType::Decimal(38, 6);
+        for data_type in data_types {
+            assert!(can_cast_types(&data_type, &decimal_type))
+        }
+        assert!(!can_cast_types(&DataType::UInt64, &decimal_type));
+
+        // test i8 to decimal type
+        let array = Int8Array::from(vec![1, 2, 3, 4, 5]);
+        let array = Arc::new(array) as ArrayRef;
+        let casted_array = cast(&array, &decimal_type).unwrap();
+        let decimal_array = casted_array
+            .as_any()
+            .downcast_ref::<DecimalArray>()
+            .unwrap();
+        assert_eq!(&decimal_type, decimal_array.data_type());
+        for i in 0..array.len() {
+            assert_eq!(
+                10_i128.pow(6) * (i as i128 + 1),
+                decimal_array.value(i as usize)
+            );
+        }
+        // test i8 to decimal type with overflow the result type
+        // the 100 will be converted to 1000_i128, but it is out of range for max value in the precision 3.
+        let array = Int8Array::from(vec![1, 2, 3, 4, 100]);
+        let array = Arc::new(array) as ArrayRef;
+        let casted_array = cast(&array, &DataType::Decimal(3, 1));
+        assert!(casted_array.is_err());
+        assert_eq!("Invalid argument error: The value of 1000 i128 is not compatible with Decimal(3,1)", casted_array.unwrap_err().to_string());
+
+        // test i16 to decimal type
+        let array = Int16Array::from(vec![1, 2, 3, 4, 5]);
+        let array = Arc::new(array) as ArrayRef;
+        let casted_array = cast(&array, &decimal_type).unwrap();
+        let decimal_array = casted_array
+            .as_any()
+            .downcast_ref::<DecimalArray>()
+            .unwrap();
+        assert_eq!(&decimal_type, decimal_array.data_type());
+        for i in 0..array.len() {
+            assert_eq!(
+                10_i128.pow(6) * (i as i128 + 1),
+                decimal_array.value(i as usize)
+            );
+        }
+
+        // test i32 to decimal type
+        let array = Int32Array::from(vec![1, 2, 3, 4, 5]);

Review comment:
       grate suggestion.
   I will try it.




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