What is the relation of protobuf message field id and field order?

user_1987788 0
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I want to understand if the messages bellow are compatible from the perspective of protobuf and serialization/deserialization.

message HelloReply {
  string message = 1;
  string personalized_message = 2;
}

message HelloReply {
  string personalized_message = 2;
  string message = 1;
}

Does the order matter for compatibility in any situation?

go message field protocol-buffers
1 Answers

The textual order is largely irrelevant, although it may impact some code generation tooling - but most languages don't care about declaration order, so even that: won't matter. The fields are still defined semantically equivalent - the numbers match the existing meaning (name) and type. It is the number that is the determining feature in identifying a field.

At the protocol level:

  • parsers must allow fields in any order
  • serializers should (but not must) write fields in ascending numerical field order
Marc_Gravell_233540
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