icexelloss commented on code in PR #34627:
URL: https://github.com/apache/arrow/pull/34627#discussion_r1149428898
##########
cpp/src/arrow/engine/substrait/expression_internal.cc:
##########
@@ -138,6 +138,77 @@ std::string EnumToString(int value, const
google::protobuf::EnumDescriptor* desc
return value_desc->name();
}
+Result<compute::Expression> FromProto(const
substrait::Expression::ReferenceSegment* ref,
+ const ExtensionSet& ext_set,
+ const ConversionOptions&
conversion_options,
+ std::optional<compute::Expression>
in_expr) {
+ auto in_ref = ref;
+ auto& out = in_expr;
+ while (ref != nullptr) {
+ switch (ref->reference_type_case()) {
+ case substrait::Expression::ReferenceSegment::kStructField: {
+ auto index = ref->struct_field().field();
+ if (!out) {
+ // Root StructField (column selection)
+ out = compute::field_ref(FieldRef(index));
+ } else if (auto out_ref = out->field_ref()) {
+ // Nested StructFields on the root (selection of struct-typed column
+ // combined with selecting struct fields)
+ out = compute::field_ref(FieldRef(*out_ref, index));
+ } else if (out->call() && out->call()->function_name ==
"struct_field") {
+ // Nested StructFields on top of an arbitrary expression
+ auto* field_options =
+
checked_cast<compute::StructFieldOptions*>(out->call()->options.get());
+ field_options->field_ref =
FieldRef(std::move(field_options->field_ref), index);
+ } else {
+ // First StructField on top of an arbitrary expression
+ out = compute::call("struct_field", {std::move(*out)},
+ arrow::compute::StructFieldOptions({index}));
+ }
+
+ // Segment handled, continue with child segment (if any)
+ if (ref->struct_field().has_child()) {
+ ref = &ref->struct_field().child();
+ } else {
+ ref = nullptr;
+ }
+ break;
+ }
+ case substrait::Expression::ReferenceSegment::kListElement: {
+ if (!out) {
+ // Root ListField (illegal)
+ return Status::Invalid(
+ "substrait::ListElement cannot take a Relation as an argument");
+ }
+
+ // ListField on top of an arbitrary expression
+ out = compute::call(
Review Comment:
don't need to support
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