[GitHub] [arrow-rs] viirya commented on a change in pull request #1263: wip. Implement DictionaryArray support in eq_dyn

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

viirya commented on a change in pull request #1263:
URL: https://github.com/apache/arrow-rs/pull/1263#discussion_r797889057



##########
File path: arrow/src/compute/kernels/comparison.rs
##########
@@ -2030,12 +2030,93 @@ macro_rules! typed_compares {
     }};
 }
 
+macro_rules! typed_dict_cmp {
+    ($LEFT: expr, $RIGHT: expr, $OP_PRIM: ident, $KT: tt) => {{
+        match ($LEFT.value_type(), $RIGHT.value_type()) {
+            (DataType::Int8, DataType::Int8) => {
+                $OP_PRIM::<$KT, Int8Type>($LEFT, $RIGHT)
+            }
+            (t1, t2) if t1 == t2 => Err(ArrowError::NotYetImplemented(format!(
+                "Comparing dictionary arrays of value type {} is not yet implemented",
+                t1
+            ))),
+            (t1, t2) => Err(ArrowError::CastError(format!(
+                "Cannot compare two dictionary arrays of different value types ({} and {})",
+                t1, t2
+            ))),
+        }
+    }};
+}
+
+macro_rules! typed_dict_compares {
+   // Applies `LEFT OP RIGHT` when `LEFT` and `RIGHT` both are `DictionaryArray`
+    ($LEFT: expr, $RIGHT: expr, $OP_PRIM: ident) => {{
+        match ($LEFT.data_type(), $RIGHT.data_type()) {
+            (DataType::Dictionary(left_key_type, _), DataType::Dictionary(right_key_type, _))=> {
+                match (left_key_type.as_ref(), right_key_type.as_ref()) {
+                    (DataType::Int8, DataType::Int8) => {
+                        let left = as_dictionary_array::<Int8Type>($LEFT);
+                        let right = as_dictionary_array::<Int8Type>($RIGHT);
+                        typed_dict_cmp!(left, right, $OP_PRIM, Int8Type)
+                    }
+                    (t1, t2) if t1 == t2 => Err(ArrowError::NotYetImplemented(format!(
+                        "Comparing dictionary arrays of type {} is not yet implemented",
+                        t1
+                    ))),
+                    (t1, t2) => Err(ArrowError::CastError(format!(
+                        "Cannot compare two dictionary arrays of different key types ({} and {})",
+                        t1, t2
+                    ))),
+                }
+            }
+            (t1, t2) => Err(ArrowError::CastError(format!(
+                "Cannot compare dictionary array with non-dictionary array ({} and {})",
+                t1, t2
+            ))),
+        }
+    }};
+}
+
+/// Perform `left == right` operation on two `DictionaryArray`s.
+/// Only when two arrays are of the same type the comparison will happen otherwise it will err
+/// with a casting error.
+pub fn eq_dict<K, T>(left: &DictionaryArray<K>, right: &DictionaryArray<K>) -> Result<BooleanArray>

Review comment:
       I don't find any `eq` implementation for `DictionaryArray`. Not sure if this is correct approach. cc @alamb 




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