tustvold commented on code in PR #4707:
URL: https://github.com/apache/arrow-rs/pull/4707#discussion_r1296119815
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arrow-array/src/array/dictionary_array.rs:
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@@ -930,6 +928,64 @@ where
}
}
+/// Returns a [`AnyDictionaryArray`] if `array` is a dictionary
+///
+/// This can be used to efficiently implement kernels for all possible
dictionary
+/// keys without needing to create specialized implementations for each key
type
+pub fn as_any_dictionary_array(array: &dyn Array) -> Option<&dyn
AnyDictionaryArray> {
+ downcast_dictionary_array! {
+ array => Some(array),
+ _ => None
+ }
+}
+
+/// A [`DictionaryArray`] with the key type erased
+///
+/// See [`as_any_dictionary_array`]
+pub trait AnyDictionaryArray: Array {
+ /// Returns the primitive keys of this dictionary as an [`Array`]
+ fn keys(&self) -> &dyn Array;
+
+ /// Returns the values of this dictionary
+ fn values(&self) -> &ArrayRef;
+
+ /// Returns the keys of this dictionary as usize
+ ///
+ /// The values for nulls will be arbitrary, but are guaranteed
+ /// to be in the range `0..self.values.len()`
+ ///
+ /// # Panic
+ ///
+ /// Panics if `values.len() == 0`
+ fn normalized_keys(&self) -> Vec<usize>;
+
+ /// Create a new [`DictionaryArray`] replacing `values` with the new values
+ ///
+ /// See [`DictionaryArray::with_values`]
+ fn with_values(&self, values: ArrayRef) -> ArrayRef;
+}
+
+impl<K: ArrowDictionaryKeyType> AnyDictionaryArray for DictionaryArray<K> {
+ fn keys(&self) -> &dyn Array {
Review Comment:
This will tie in nicely with #4705
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