Recursive Structures in protobuffers

[pbjson]

Hello,

Has anyone seen the following structure in protobuffer?


message KeyValue{

 required string key=1;
 optional string  value=2;
 optional KeyValue key_value=10;

}

this is a circular reference and how would you resolve this if you have convert this to a flat structure of primitives for eg: to be converted to a hive schema.

eg: keyvalue<key:string,value string, key_value:string>

Has anyone come across such a situation and any better way to do this?

Thanks in advance.

[Marc Gravell]

Protobuf supports recursive schemes - but note that each object is separate (it is a tree, not a graph). For example, descriptor.proto includes the self-referential "DescriptorProto" (which is a "message" in language terms)

// Describes a message type.

message DescriptorProto {

optional string name = 1;

repeated FieldDescriptorProto field = 2;

repeated FieldDescriptorProto extension = 6;

repeated DescriptorProto nested_type = 3;

repeated EnumDescriptorProto enum_type = 4;

message ExtensionRange {

optional int32 start = 1;

optional int32 end = 2;

}

repeated ExtensionRange extension_range = 5;

optional MessageOptions options = 7;

}

Marc

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