Parth Upadhyay created SPARK-43051:
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Summary: Allow materializing zero values when deserializing
protobuf messages
Key: SPARK-43051
URL: https://issues.apache.org/jira/browse/SPARK-43051
Project: Spark
Issue Type: Improvement
Components: Protobuf
Affects Versions: 3.4.0
Reporter: Parth Upadhyay
Currently, when deserializing protobufs using {{{}from_protobuf{}}}, fields
that are not explicitly present in the serialized message are deserialized as
{{null}} in the resulting struct. (In proto3, this also includes fields that
have been explicitly set to their zero value, as it is not distinguishable in
the serialized format.
[https://protobuf.dev/programming-guides/field_presence/])
For example, given a message format like
{code:java}
syntax = "proto3";
message SearchRequest {
string query = 1;
int32 page_number = 2;
int32 result_per_page = 3;
}
{code}
and an example message like
{code:python}
SearchRequest(query = "", page_number = 10)
{code}
the result from calling {{from_protobuf}} on the serialized form of the above
message would be
{code:json}
{"query": null, "page_number": 10, "result_per_page": null}
{code}
In proto3, all fields are considered optional and have default values
([https://protobuf.dev/programming-guides/proto3/#default]), and reader clients
in some languages (e.g. go, scala) will fill in that default value when reading
the protobuf. It could be useful to make this configurable so that zero values
can optionally be materialized if desired.
Concretely, in the example above, we might want to deserialize it instead as
{code:json}
{"query": "", "page_number": 10, "result_per_page": 0}
{code}
In this ticket I propose implementing a way to get the above functionality. In
the linked PR, i've done it by adding an option, {{materializeZeroValues}} that
can be passed to the options map in the {{from_protobuf}} function to enable
this behavior. However i'd love any feedback on if i've understood the problem
correctly and if the implementation makes sense.
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