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https://issues.apache.org/jira/browse/AVRO-1827?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15244404#comment-15244404
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Ryan Blue commented on AVRO-1827:
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[~jakub_kahovec], thanks for finding this and fixing it. I agree with you that
this is the correct behavior. The patch looks fine to me (other than one nit:
// should be indented with the comment) but I'd like to see some tests that
define the correct behavior and validate it. Could you add those? Thanks!
> Handling correctly optional fields when converting Protobuf to Avro
> -------------------------------------------------------------------
>
> Key: AVRO-1827
> URL: https://issues.apache.org/jira/browse/AVRO-1827
> Project: Avro
> Issue Type: Improvement
> Affects Versions: 1.7.7, 1.8.0
> Reporter: Jakub Kahovec
> Attachments: AVRO-1827.patch
>
>
> Hello,
> as of the current implementation of converting protobuf files into avro
> format, protobuf optional fields are being given default values in the avro
> schema if not specified explicitly.
> So for instance when the protobuf field is defined as
> {quote}
> optional int64 fieldInt64 = 1;
> {quote}
> in the avro schema it appears as
> {quote}
> "name" : "fieldInt64",
> "type" : "long",
> "default" : 0
> {quote}
> The problem with this implementation is that we are losing information about
> whether the field was present or not in the original protobuf, as when we ask
> for this field's value in avro we will be given the default value.
> What I'm proposing instead is that if the field in the protobuf is defined as
> optional and has no default value then the generated avro schema type will us
> a union comprising the matching type and null type with default value null.
> It is going to look like this:
> {quote}
> "name" : "fieldIn64",
> "type" : [ "null", "long" ],
> "default" : null
> {quote}
> I'm aware that is a breaking change but I think that is the proper way how to
> handle optional fields.
> I've also created a patch which fixes the conversion
> Jakub
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