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https://issues.apache.org/jira/browse/AVRO-1335?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pierre de Freminville updated AVRO-1335:
----------------------------------------
Attachment: AVRO-1335.patch
Included patch fixes issue with default values not being printed out when
serializing the schema. Tests have been added to test this functionnality.
Problem is described in the mail to the user list:
http://mail-archives.apache.org/mod_mbox/avro-user/201504.mbox/%3CDUB130-W77519D4146DB3E05C81951A1E60%40phx.gbl%3E
> 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
> 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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