Jefffrey commented on code in PR #8912:
URL: https://github.com/apache/arrow-rs/pull/8912#discussion_r2613793286
##########
arrow-cast/src/cast/dictionary.rs:
##########
@@ -28,111 +28,92 @@ pub(crate) fn dictionary_cast<K: ArrowDictionaryKeyType>(
) -> Result<ArrayRef, ArrowError> {
use DataType::*;
- match to_type {
- Dictionary(to_index_type, to_value_type) => {
- 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(),
- )
- })?;
+ let array = array.as_dictionary::<K>();
+ let from_child_type = array.values().data_type();
+ match (from_child_type, to_type) {
+ (_, Dictionary(to_index_type, to_value_type)) => {
+ dictionary_to_dictionary_cast(array, to_index_type, to_value_type,
cast_options)
+ }
+ // `unpack_dictionary` can handle Utf8View/BinaryView types, but
incurs unnecessary data
+ // copy of the value buffer. Fast path which avoids copying underlying
values buffer.
+ // TODO: handle LargeUtf8/LargeBinary -> View (need to check offsets
can fit)
+ // TODO: handle cross types (String -> BinaryView, Binary ->
StringView)
+ // (need to validate utf8?)
+ (Utf8, Utf8View) => view_from_dict_values::<K, Utf8Type,
StringViewType>(
+ array.keys(),
+ array.values().as_string::<i32>(),
+ ),
+ (Binary, BinaryView) => view_from_dict_values::<K, BinaryType,
BinaryViewType>(
+ array.keys(),
+ array.values().as_binary::<i32>(),
+ ),
Review Comment:
Raised for tracking: https://github.com/apache/arrow-rs/issues/8985
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