pitrou commented on a change in pull request #6959:
URL: https://github.com/apache/arrow/pull/6959#discussion_r412310009
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File path: cpp/src/arrow/ipc/metadata_internal.cc
##########
@@ -756,10 +737,35 @@ Status FieldFromFlatbuffer(const flatbuf::Field* field,
DictionaryMemo* dictiona
RETURN_NOT_OK(IntFromFlatbuffer(int_data, &index_type));
ARROW_ASSIGN_OR_RAISE(type,
DictionaryType::Make(index_type, type,
encoding->isOrdered()));
- *out = ::arrow::field(field_name, type, field->nullable(), metadata);
- RETURN_NOT_OK(dictionary_memo->AddField(encoding->id(), *out));
- } else {
- *out = ::arrow::field(field_name, type, field->nullable(), metadata);
+ dictionary_id = encoding->id();
+ }
+
+ // 4. Is it an extension type?
+ if (metadata != nullptr) {
+ // Look for extension metadata in custom_metadata field
+ int name_index = metadata->FindKey(kExtensionTypeKeyName);
+ if (name_index != -1) {
+ std::string type_name = metadata->value(name_index);
+ int data_index = metadata->FindKey(kExtensionMetadataKeyName);
+ std::string type_data = data_index == -1 ? "" :
metadata->value(data_index);
+
+ std::shared_ptr<ExtensionType> ext_type = GetExtensionType(type_name);
+ if (ext_type != nullptr) {
+ ARROW_ASSIGN_OR_RAISE(type, ext_type->Deserialize(type, type_data));
+ // Remove the metadata, for faithful roundtripping
+ RETURN_NOT_OK(metadata->DeleteMany({name_index, data_index}));
Review comment:
@wesm Do you opine to this?
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