Jakub Kahovec created AVRO-1827:
-----------------------------------
Summary: 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: 1.8.0, 1.7.7
Reporter: Jakub Kahovec
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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