justaparth commented on code in PR #40686:
URL: https://github.com/apache/spark/pull/40686#discussion_r1181141599
##########
connector/protobuf/src/main/scala/org/apache/spark/sql/protobuf/ProtobufDeserializer.scala:
##########
@@ -299,6 +298,29 @@ private[sql] class ProtobufDeserializer(
}
}
+ private def getFieldValue(record: DynamicMessage, field: FieldDescriptor):
AnyRef = {
+ // We return a value if one of:
+ // - the field is repeated
+ // - the field is explicitly present in the serialized proto
+ // - the field is proto2 with a default
+ // - field presence is not available and materializeZeroValues is set
+ //
+ // Repeated fields have to be treated separately as they cannot have
`hasField`
+ // called on them. And we only materialize zero values for fields without
presence
+ // information because that flag controls the behavior for those fields in
the ambiguous
+ // case of "unset" or "set to zero value". See the docs in
[[ProtobufOptions]] for more
+ // details.
+ if (
+ field.isRepeated
+ || record.hasField(field)
+ || field.hasDefaultValue
+ || (!field.hasPresence && this.materializeZeroValues)) {
Review Comment:
but, in any case i've actually restructured the comment a bit, i wonder if
its more clear now, do you want to take a look?
##########
connector/protobuf/src/main/scala/org/apache/spark/sql/protobuf/utils/ProtobufOptions.scala:
##########
@@ -46,6 +46,42 @@ private[sql] class ProtobufOptions(
// record has more depth than the allowed value for recursive fields, it
will be truncated
// and corresponding fields are ignored (dropped).
val recursiveFieldMaxDepth: Int =
parameters.getOrElse("recursive.fields.max.depth", "-1").toInt
+
+ // For fields without presence information, there is ambiguity in serialized
protos
Review Comment:
done!
##########
connector/protobuf/src/main/scala/org/apache/spark/sql/protobuf/utils/ProtobufOptions.scala:
##########
@@ -46,6 +46,42 @@ private[sql] class ProtobufOptions(
// record has more depth than the allowed value for recursive fields, it
will be truncated
// and corresponding fields are ignored (dropped).
val recursiveFieldMaxDepth: Int =
parameters.getOrElse("recursive.fields.max.depth", "-1").toInt
+
+ // For fields without presence information, there is ambiguity in serialized
protos
+ // as to whether the field was never written or was written with its zero
value.
+ // This is because such fields are not serialized if they contain their zero
value.
+ // This includes most fields in proto3.
+ // Ref: https://protobuf.dev/programming-guides/field_presence
+ // https://protobuf.dev/programming-guides/field_presence/
+ // #presence-in-tag-value-stream-wire-format-serialization
+ //
+ // By default, this library deserializes both cases as null. However, this
flag can
+ // choose to explicitly deserialize them as the zero value for the type, as
+ // libraries in some other will languages do.
+ //
+ // For example, if we have a proto like
+ // ```
+ // syntax = "proto3";
+ // message Person {
+ // string name = 1;
+ // int64 age = 2;
Review Comment:
👍
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