[GitHub] [arrow-rs] alamb commented on a change in pull request #1372: Add benchmark and take_iter_unchecked

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

alamb commented on a change in pull request #1372:
URL: https://github.com/apache/arrow-rs/pull/1372#discussion_r817798695



##########
File path: arrow/src/compute/kernels/comparison.rs
##########
@@ -2214,19 +2214,23 @@ macro_rules! compare_dict_op {
             ));
         }
 
-        let left_iter = $left
-            .values()
-            .as_any()
-            .downcast_ref::<$value_ty>()
-            .unwrap()
-            .take_iter($left.keys_iter());
-
-        let right_iter = $right
-            .values()
-            .as_any()
-            .downcast_ref::<$value_ty>()
-            .unwrap()
-            .take_iter($right.keys_iter());
+        let left_iter = unsafe {

Review comment:
       ```suggestion
           // Safety justification: Since the inputs are valid Arrow arrays, all values are
           // valid indexes into the dictionary (which is verified during construction)
   
           let left_iter = unsafe {
   ```




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