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From Jeff Klukas <>
Subject Evolving a Coder for an added field
Date Fri, 02 Nov 2018 12:43:59 GMT
I'm adding a new lastModifiedMillis field to MatchResult.Metadata [0] which
requires also updating MetadataCoder, but it's not clear to me whether
there are guidelines to follow when evolving a type when that changes the

Is a user allowed to update Beam library versions as part of updating a
pipeline? If so, there could be a situation where an updated pipeline is
reading state that includes Metadata encoded without the new
lastModifiedMillis field, which would cause a CodingException to be thrown.

Is there prior art for evolving a type and its Coder? Should I be defensive
and catch CodingException when attempting to decode the new field,
providing a default value?


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