[GitHub] [arrow] mqy commented on a change in pull request #9193: ARROW-11239: [Rust] Show some unit test failures

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

mqy commented on a change in pull request #9193:
URL: https://github.com/apache/arrow/pull/9193#discussion_r558885348



##########
File path: rust/arrow/src/array/data.rs
##########
@@ -219,17 +219,15 @@ impl ArrayData {
     ///
     /// Panics if `offset + length > self.len()`.
     pub fn slice(&self, offset: usize, length: usize) -> ArrayData {
-        assert!((offset + length) <= self.len());
-
-        let mut new_data = self.clone();
-
-        new_data.len = length;
-        new_data.offset = offset + self.offset;
-
-        new_data.null_count =
-            count_nulls(new_data.null_buffer(), new_data.offset, new_data.len);
+        self.copy_range(offset, length)
+    }
 
-        new_data
+    fn copy_range(&self, offset: usize, length: usize) -> ArrayData {
+        assert!((offset + length) <= self.len());
+        let arrays = vec![self];

Review comment:
       > Possible performance speedup
   Totally wrong, the benchmark of `array_slice` shows 4x - 11x regression.




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