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https://issues.apache.org/jira/browse/AVRO-1335?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16140653#comment-16140653
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ASF GitHub Bot commented on AVRO-1335:
--------------------------------------
GitHub user vimota opened a pull request:
https://github.com/apache/avro/pull/241
AVRO-1335: Adds C++ support for default values in schema serializatio…
…n to json.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/vimota/avro changes
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/avro/pull/241.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #241
----
commit 6c2539769e004c01a0dca5978288ea3072f63e8f
Author: Victor Mota <[email protected]>
Date: 2017-08-20T01:56:03Z
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
> 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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