[GitHub] [arrow-rs] liukun4515 commented on a diff in pull request #2649: support `CastOption` for casting numeric

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

liukun4515 commented on code in PR #2649:
URL: https://github.com/apache/arrow-rs/pull/2649#discussion_r963202388


##########
arrow/src/compute/kernels/cast.rs:
##########
@@ -1456,21 +1621,62 @@ where
 }
 
 /// Convert Array into a PrimitiveArray of type, and apply numeric cast
-fn cast_numeric_arrays<FROM, TO>(from: &ArrayRef) -> Result<ArrayRef>
+fn cast_numeric_arrays<FROM, TO>(
+    from: &ArrayRef,
+    cast_options: &CastOptions,
+) -> Result<ArrayRef>
 where
     FROM: ArrowNumericType,
     TO: ArrowNumericType,
     FROM::Native: num::NumCast,
     TO::Native: num::NumCast,
 {
-    Ok(Arc::new(numeric_cast::<FROM, TO>(
-        from.as_any()
-            .downcast_ref::<PrimitiveArray<FROM>>()
-            .unwrap(),
-    )))
+    if cast_options.safe {
+        // If the value can't be casted to the `TO::Native`, return null
+        Ok(Arc::new(numeric_cast::<FROM, TO>(
+            from.as_any()
+                .downcast_ref::<PrimitiveArray<FROM>>()
+                .unwrap(),
+        )))
+    } else {
+        // If the value can't be casted to the `TO::Native`, return error
+        Ok(Arc::new(numeric_cast_with_error::<FROM, TO>(
+            from.as_any()
+                .downcast_ref::<PrimitiveArray<FROM>>()
+                .unwrap(),
+        )?))
+    }
 }
 
-/// Natural cast between numeric types
+// Natural cast between numeric types
+// If the value of T can't be casted to R, will throw error
+fn numeric_cast_with_error<T, R>(from: &PrimitiveArray<T>) -> Result<PrimitiveArray<R>>
+where
+    T: ArrowNumericType,
+    R: ArrowNumericType,
+    T::Native: num::NumCast,
+    R::Native: num::NumCast,
+{
+    let iter = from
+        .iter()
+        .map(|v| match v {
+            None => Ok(None),
+            Some(value) => match num::cast::cast::<T::Native, R::Native>(value) {
+                None => Err(ArrowError::CastError(format!(
+                    "Can't cast value {:?} to type {}",
+                    value,
+                    R::DATA_TYPE
+                ))),
+                Some(v) => Ok(Some(v)),
+            },
+        })
+        .collect::<Result<Vec<Option<R::Native>>>>()?;
+
+    Ok(unsafe { PrimitiveArray::<R>::from_trusted_len_iter(iter) })

Review Comment:
   Do you mean use the `try_from_trusted_len_iter` API for the `MutableBuffer` or `Buffer`?
   Does it can fit this result?
   



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