add a roundtrip test

cpp/src/parquet/arrow/arrow_reader_writer_test.cc

@@ -4093,6 +4093,62 @@ TEST(TestArrowReaderAdHoc, OldDataPageV2) {
  TryReadDataFile(path);
 }
 
+TEST(TestArrowReaderAdHoc, LegacyTwoLevelList) {
+ // Create schema with a nested list of two-level encoding:
+ constexpr std::string_view kExpectedSchema =
+ "required group field_id=-1 schema {\n"
+ " optional group field_id=-1 nested_list (List) {\n"
+ " repeated group field_id=-1 array (List) {\n"
+ " repeated int32 field_id=-1 array;\n"
+ " }\n"
+ " }\n"
+ "}\n";
+ auto inner_element = PrimitiveNode::Make("array", Repetition::REPEATED, Type::INT32);
+ auto outer_element = GroupNode::Make("array", Repetition::REPEATED, {inner_element},
+ ConvertedType::LIST);
+ auto nested_list = GroupNode::Make("nested_list", Repetition::OPTIONAL, {outer_element},
+ ConvertedType::LIST);
+ auto schema_node = GroupNode::Make("schema", Repetition::REQUIRED, {nested_list});
+
+ // Create a Parquet writer to write values of nested list
+ auto sink = CreateOutputStream();
+ auto file_writer = ParquetFileWriter::Open(
+ sink, std::dynamic_pointer_cast<schema::GroupNode>(schema_node));
+ auto row_group_writer = file_writer->AppendRowGroup();
+ auto int_writer = dynamic_cast<Int32Writer*>(row_group_writer->NextColumn());
+ ASSERT_TRUE(int_writer != nullptr);
+
+ // Directly write a single row of nested list: [[1, 2],[3, 4]]
+ constexpr int64_t kNumValues = 4;
+ std::array<int16_t, kNumValues> rep_levels = {0, 2, 1, 2};
+ std::array<int16_t, kNumValues> def_levels = {3, 3, 3, 3};
+ std::array<int32_t, kNumValues> values = {1, 2, 3, 4};
+ int_writer->WriteBatch(kNumValues, def_levels.data(), rep_levels.data(), values.data());
+ file_writer->Close();
+
+ // Read schema and verify it applies two-level encoding of list type
+ ASSERT_OK_AND_ASSIGN(auto buffer, sink->Finish());
+ auto source = std::make_shared<::arrow::io::BufferReader>(buffer);
+ auto file_reader = ParquetFileReader::Open(source);
+ ASSERT_EQ(kExpectedSchema, file_reader->metadata()->schema()->ToString());
+
+ // Read and verify data
+ std::unique_ptr<FileReader> reader;
+ ASSERT_OK(FileReader::Make(default_memory_pool(), std::move(file_reader), &reader));
+ std::shared_ptr<Table> table;
+ ASSERT_OK(reader->ReadTable(&table));
+
+ auto arrow_inner_element =
+ ::arrow::field("array", ::arrow::int32(), /*nullable=*/false);
+ auto arrow_outer_element =
+ ::arrow::field("array", ::arrow::list(arrow_inner_element), /*nullable=*/false);
+ auto arrow_list = ::arrow::list(arrow_outer_element);
+ auto arrow_schema =
+ ::arrow::schema({::arrow::field("nested_list", arrow_list, /*nullable=*/true)});
+ auto expected_table = ::arrow::TableFromJSON(arrow_schema, {R"([[[[1,2],[3,4]]]])"});
+ ::arrow::AssertTablesEqual(*expected_table, *table);
+}
+
 class TestArrowReaderAdHocSparkAndHvr
  : public ::testing::TestWithParam<
  std::tuple<std::string, std::shared_ptr<DataType>>> {};