pitrou commented on a change in pull request #10606:
URL: https://github.com/apache/arrow/pull/10606#discussion_r660748979
##########
File path: cpp/src/arrow/compute/kernels/vector_selection.cc
##########
@@ -1668,6 +1668,66 @@ struct ListImpl : public Selection<ListImpl<Type>, Type>
{
}
};
+struct DenseUnionImpl : public Selection<DenseUnionImpl, DenseUnionType> {
+ using Base = Selection<DenseUnionImpl, DenseUnionType>;
+ LIFT_BASE_MEMBERS();
+
+ typename TypeTraits<DenseUnionType>::ValueOffsetBuilderType
value_offset_builder;
+ typename TypeTraits<DenseUnionType>::ChildIdBuilderType child_id_builder;
+ std::vector<int8_t> type_codes;
+
+ DenseUnionImpl(KernelContext* ctx, const ExecBatch& batch, int64_t
output_length,
+ Datum* out)
+ : Base(ctx, batch, output_length, out),
+ value_offset_builder(ctx->memory_pool()),
+ child_id_builder(ctx->memory_pool()) {
+ DenseUnionArray typed_values(this->values);
+ type_codes = typed_values.union_type()->type_codes();
+ }
+
+ template <typename Adapter>
+ Status GenerateOutput() {
+ DenseUnionArray typed_values(this->values);
+ Adapter adapter(this);
+ RETURN_NOT_OK(adapter.Generate(
+ [&](int64_t index) {
+ auto child_id = typed_values.child_id(index);
+ child_id_builder.UnsafeAppend(type_codes[child_id]);
+ auto value_offset = typed_values.value_offset(index);
+ value_offset_builder.UnsafeAppend(value_offset);
+ return Status::OK();
+ },
+ // TODO: not able to handle null case
+ VisitNoop));
+ return Status::OK();
+ }
+
+ Status Init() override {
+ RETURN_NOT_OK(child_id_builder.Reserve(output_length));
+ RETURN_NOT_OK(value_offset_builder.Reserve(output_length));
+ return Status::OK();
+ }
+
+ Status Finish() override {
+ std::shared_ptr<Array> child_ids;
+ std::shared_ptr<Array> value_offsets;
+ RETURN_NOT_OK(child_id_builder.Finish(&child_ids));
+ RETURN_NOT_OK(value_offset_builder.Finish(&value_offsets));
+
+ DenseUnionArray typed_values(this->values);
+ auto num_fields = typed_values.num_fields();
+ ArrayVector child_arrays;
+ child_arrays.reserve(num_fields);
+ BufferVector buffers = {nullptr, checked_cast<const
Int8Array&>(*child_ids).values(),
+ checked_cast<const
Int32Array&>(*value_offsets).values()};
+ *out = ArrayData(typed_values.type(), child_ids->length(),
std::move(buffers), 0);
+ for (int i = 0; i < typed_values.num_fields(); i++) {
+ out->child_data.push_back(typed_values.field(i)->data());
Review comment:
Hmm, if I understand correctly, you're reusing the full child arrays
even if only a small fraction of them was taken? If so, this seems wasteful.
I think this can be done otherwise: maintain maps of the original offsets to
the taken offsets, per child. This will admittedly use a lot of temporary
storage (perhaps this can be done one child at a time?), but at least the final
union array will be reasonably compact.
@bkietz What do you think?
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
