[GitHub] [arrow-rs] alamb commented on a change in pull request #984: Add comparison kernels for DictionaryArray

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

alamb commented on a change in pull request #984:
URL: https://github.com/apache/arrow-rs/pull/984#discussion_r760595599



##########
File path: arrow/src/compute/kernels/comparison.rs
##########
@@ -200,6 +201,42 @@ macro_rules! compare_op_scalar_primitive {
     }};
 }
 
+macro_rules! compare_dict_op_scalar {
+    ($left:expr, $right:expr, $op:expr) => {{
+        let null_bit_buffer = $left
+            .data()
+            .null_buffer()
+            .map(|b| b.bit_slice($left.offset(), $left.len()));
+
+        let values = $left
+            .values()
+            .as_any()
+            .downcast_ref::<StringArray>()

Review comment:
       I am very sorry for confusing this conversation with mentioning `dyn_xx_lit`. 
   
   What I was (inarticulately) trying to say was that once you have `eq_dict_scalar` (and you will likely also need `eq_dict_scalar_utf8`) we will end up with several different ways to compare an array to a scalar, depending on the array type
   
   So I was thinking ahead to adding functions like
   
   ```rust
   fn eq_scalar_utf8_dyn(array: dyn &Array, right: &str) -> Boolean {
     // do dispatch to the right kernel based on type of array
   }
   ```
   
   But definitely not for this PR




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