[GitHub] [arrow] wgtmac opened a new issue, #35297: [C++][IPC] Schema deserialization does not preserve metadata of map field

["wgtmac (via GitHub)" <gi...@apache.org>]

wgtmac opened a new issue, #35297:
URL: https://github.com/apache/arrow/issues/35297

   ### Describe the bug, including details regarding any error messages, version, and platform.
   
   The code below does not deal with field metadata like `nullable` and `metadata` of key and item sub-fields of map type.
   
   ```cpp
   Status ConcreteTypeFromFlatbuffer(flatbuf::Type type, const void* type_data,
                                     FieldVector children, std::shared_ptr<DataType>* out) {
     switch (type) {
       case flatbuf::Type::NONE:
         return Status::Invalid("Type metadata cannot be none");
       ...
       case flatbuf::Type::Map:
         if (children.size() != 1) {
           return Status::Invalid("Map must have exactly 1 child field");
         }
         if (children[0]->nullable() || children[0]->type()->id() != Type::STRUCT ||
             children[0]->type()->num_fields() != 2) {
           return Status::Invalid("Map's key-item pairs must be non-nullable structs");
         }
         if (children[0]->type()->field(0)->nullable()) {
           return Status::Invalid("Map's keys must be non-nullable");
         } else {
           auto map = static_cast<const flatbuf::Map*>(type_data);
           *out = std::make_shared<MapType>(children[0]->type()->field(0)->type(),
                                            children[0]->type()->field(1)->type(),
                                            map->keysSorted());
         }
         return Status::OK();
       ...
       default:
         return Status::Invalid("Unrecognized type: " + ToChars(static_cast<int>(type)));
     }
   }
   ```
   
   The issue can be easily reproduced by a roundtrip test of schema serialization with a non-null map item field.
   
   ### Component(s)
   
   C++


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[GitHub] [arrow] wjones127 closed issue #35297: [C++][IPC] Schema deserialization does not preserve metadata of map field

["wjones127 (via GitHub)" <gi...@apache.org>]

wjones127 closed issue #35297: [C++][IPC] Schema deserialization does not preserve metadata of map field
URL: https://github.com/apache/arrow/issues/35297


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