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https://issues.apache.org/jira/browse/AVRO-1335?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16649485#comment-16649485
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ASF subversion and git services commented on AVRO-1335:
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Commit 377bc5848d066a851560fb921b6b77996f7d150f in avro's branch
refs/heads/master from [~vimota]
[ https://gitbox.apache.org/repos/asf?p=avro.git;h=377bc58 ]
AVRO-1335: Adds C++ support for default values in schema serialization to json.
> C++ should support field default values
> ---------------------------------------
>
> Key: AVRO-1335
> URL: https://issues.apache.org/jira/browse/AVRO-1335
> Project: Avro
> Issue Type: Improvement
> Components: c++
> Affects Versions: 1.7.4
> Reporter: Bin Guo
> Assignee: Victor Mota
> Priority: Major
> Attachments: AVRO-1335.patch
>
>
> We found that resolvingDecoder could not provide bidirectional compatibility
> between different version of schemas.
> Especially for records, for example:
> {code:title=First schema}
> {
> "type": "record",
> "name": "TestRecord",
> "fields": [
> {
> "name": "MyData",
> "type": {
> "type": "record",
> "name": "SubData",
> "fields": [
> {
> "name": "Version1",
> "type": "string"
> }
> ]
> }
> },
> {
> "name": "OtherData",
> "type": "string"
> }
> ]
> }
> {code}
> {code:title=Second schema}
> {
> "type": "record",
> "name": "TestRecord",
> "fields": [
> {
> "name": "MyData",
> "type": {
> "type": "record",
> "name": "SubData",
> "fields": [
> {
> "name": "Version1",
> "type": "string"
> },
> {
> "name": "Version2",
> "type": "string"
> }
> ]
> }
> },
> {
> "name": "OtherData",
> "type": "string"
> }
> ]
> }
> {code}
> Say, node A knows only the first schema and node B knows the second schema,
> and the second schema has more fields.
> Any data generated by node B can be resolved by first schema 'cause the
> additional field is marked as skipped.
> But data generated by node A can not be resolved by second schema and throws
> an exception *"Don't know how to handle excess fields for reader."*
> This is because data is resolved exactly according to the auto-generated
> codec_traits which trying to read the excess field.
> The problem is we just can not only ignore the excess field in record, since
> the data after the troublesome record also needs to be resolved.
> Actually this problem stucked us for a very long time.
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