Fix total_byte_size in Parquet row group metadata (#14802)

The `total_byte_size` field in the row group metadata should be "[t]otal byte size of all the uncompressed column data in this row group". cuDF currently populates this field with the _compressed_ size. This PR fixes that and adds a test.

Authors:
  - Ed Seidl (https://github.com/etseidl)
  - Vyas Ramasubramani (https://github.com/vyasr)

Approvers:
  - Vukasin Milovanovic (https://github.com/vuule)
  - Vyas Ramasubramani (https://github.com/vyasr)
  - https://github.com/nvdbaranec

URL: #14802

cpp/src/io/parquet/writer_impl.cu

@@ -2074,7 +2074,7 @@ auto convert_table_to_parquet_data(table_input_metadata& table_meta,
           need_sync = true;
         }
 
-        row_group.total_byte_size += ck.compressed_size;
+        row_group.total_byte_size += ck.bfr_size;
         column_chunk_meta.total_uncompressed_size = ck.bfr_size;
         column_chunk_meta.total_compressed_size   = ck.compressed_size;
       }

cpp/tests/io/parquet_writer_test.cpp

@@ -1401,6 +1401,33 @@ TEST_F(ParquetWriterTest, EmptyMinStringStatistics)
   EXPECT_EQ(max_value, std::string(max_val));
 }
 
+TEST_F(ParquetWriterTest, RowGroupMetadata)
+{
+  using column_type      = int;
+  constexpr int num_rows = 1'000;
+  auto const ones        = thrust::make_constant_iterator(1);
+  auto const col =
+    cudf::test::fixed_width_column_wrapper<column_type>{ones, ones + num_rows, no_nulls()};
+  auto const table = table_view({col});
+
+  auto const filepath = temp_env->get_temp_filepath("RowGroupMetadata.parquet");
+  // force PLAIN encoding to make size calculation easier
+  cudf::io::parquet_writer_options opts =
+    cudf::io::parquet_writer_options::builder(cudf::io::sink_info{filepath}, table)
+      .dictionary_policy(cudf::io::dictionary_policy::NEVER)
+      .compression(cudf::io::compression_type::ZSTD);
+  cudf::io::write_parquet(opts);
+
+  // check row group metadata to make sure total_byte_size is the uncompressed value
+  auto const source = cudf::io::datasource::create(filepath);
+  cudf::io::parquet::detail::FileMetaData fmd;
+  read_footer(source, &fmd);
+
+  ASSERT_GT(fmd.row_groups.size(), 0);
+  EXPECT_GE(fmd.row_groups[0].total_byte_size,
+            static_cast<int64_t>(num_rows * sizeof(column_type)));
+}
+
 // See #14772.
 // zStandard compression cannot currently be used with V2 page headers due to buffer
 // alignment issues.
@@ -1416,6 +1443,7 @@ TEST_F(ParquetWriterTest, ZstdWithV2Header)
   EXPECT_THROW(cudf::io::write_parquet(out_opts), cudf::logic_error);
 }
 
+/////////////////////////////////////////////////////////////
 // custom mem mapped data sink that supports device writes
 template <bool supports_device_writes>
 class custom_test_memmap_sink : public cudf::io::data_sink {