dmitry-chirkov-dremio commented on code in PR #51647:
URL: https://github.com/apache/arrow/pull/51647#discussion_r4335242847
##########
cpp/src/arrow/util/list_util.cc:
##########
@@ -190,8 +192,78 @@ int64_t SumOfListViewSizes(const ArraySpan& input) {
return sum;
}
+/// \param list_view A LIST_VIEW or LARGE_LIST_VIEW array
+template <typename DestListType, typename SrcListViewType>
+Result<std::shared_ptr<ArrayData>> ListFromListViewImpl(const ArraySpan&
list_view,
+ MemoryPool* pool) {
+ using src_offset_type = typename SrcListViewType::offset_type;
+ using ListBuilderType = typename TypeTraits<DestListType>::BuilderType;
+
+ const auto& list_view_type = checked_cast<const
SrcListViewType&>(*list_view.type);
+ const auto& value_type = list_view_type.value_type();
+ // The value type is carried over, so that callers may cast the child.
+ auto list_type = std::make_shared<DestListType>(value_type);
+
+ ARROW_ASSIGN_OR_RAISE(auto sum_of_sizes, SumOfLogicalListSizes(list_view));
+ ARROW_ASSIGN_OR_RAISE(std::shared_ptr<ArrayBuilder> value_builder,
+ MakeBuilder(value_type, pool));
Review Comment:
This makes casts with extension children fail. A valid
list_view<arrow.bool8> can currently be cast to list<arrow.bool8> or
list<int8>. Both now fail because MakeBuilder does not support extension types.
Let's preserve these casts and add regression tests for both targets.
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