Clarify if ReadResponse can/should contain duplicates or not

[smolkaj]

Forking off from #476.

The following is a valid read request:

device_id: <ID>
entities {
  table_entry { }  # read all table entries for all tables
}
entities {
  table_entry { }  # read all table entries for all tables
}

Should this read all table entries twice or just a single time? The spec doesn't seem to specify which one we want at the moment.

[jonathan-dilorenzo]

It seems to be allowed, but not required to contain duplicates if there are overlapping requests. This is the relevant paragraph from section 13.3.1:

The P4Runtime server is not required to perform any optimization (e.g. merge two requests in the batch if one is a subset of other). As a result of this, it is possible for the ReadResponse to contain the same entity more than once. If performance is a concern, the P4Runtime client should handle this merging.

[smolkaj]

Thanks for the clarification, closing the issue.