tustvold commented on code in PR #4406:
URL: https://github.com/apache/arrow-rs/pull/4406#discussion_r1228184372
##########
arrow-cast/src/cast.rs:
##########
@@ -3466,34 +3466,21 @@ fn unpack_dictionary<K>(
where
K: ArrowDictionaryKeyType,
{
- let dict_array = array
- .as_any()
- .downcast_ref::<DictionaryArray<K>>()
- .ok_or_else(|| {
- ArrowError::ComputeError(
- "Internal Error: Cannot cast dictionary to DictionaryArray of
expected type".to_string(),
- )
- })?;
-
- // attempt to cast the dict values to the target type
- // use the take kernel to expand out the dictionary
+ let dict_array = array.as_dictionary::<K>();
let cast_dict_values = cast_with_options(dict_array.values(), to_type,
cast_options)?;
-
- // Note take requires first casting the indices to u32
- let keys_array: ArrayRef =
- Arc::new(PrimitiveArray::<K>::from(dict_array.keys().to_data()));
- let indices = cast_with_options(&keys_array, &DataType::UInt32,
cast_options)?;
- let u32_indices =
- indices
- .as_any()
- .downcast_ref::<UInt32Array>()
- .ok_or_else(|| {
- ArrowError::ComputeError(
- "Internal Error: Cannot cast dict indices to
UInt32".to_string(),
- )
- })?;
-
- take(cast_dict_values.as_ref(), u32_indices, None)
+ let keys = dict_array.keys();
+ match K::DATA_TYPE {
+ DataType::Int32 => {
Review Comment:
Theoretically we could pass the keys directly to take, this approach avoids
additional codegen, and also appears to be faster for reasons I don't
understand :sweat_smile:
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