reader_writer_benchmark.patch

diff --git forkSrcPrefix/cpp/src/parquet/arrow/reader_writer_benchmark.cc forkDstPrefix/cpp/src/parquet/arrow/reader_writer_benchmark.cc
index 95c4a659297d93f0927a8f36bb25607b15e5a0fa..d450431eae5133daf24066f8d01701cd34af63c9 100644
--- forkSrcPrefix/cpp/src/parquet/arrow/reader_writer_benchmark.cc
+++ forkDstPrefix/cpp/src/parquet/arrow/reader_writer_benchmark.cc
@@ -15,6 +15,8 @@
 // specific language governing permissions and limitations
 // under the License.
 
+#include <sys/_types/_int64_t.h>
+#include "arrow/io/file.h"
 #include "benchmark/benchmark.h"
 
 #include <array>
@@ -247,6 +249,51 @@ BENCHMARK(BM_WriteBinaryColumn)
     ->Args({50, kInfiniteUniqueValues})
     ->Args({99, kInfiniteUniqueValues});
 
+static void BM_WriteBinaryColumnMultithreaded(::benchmark::State& state) {
+  // hack: load parquet from disk
+  auto pq_file = ::arrow::io::ReadableFile::Open("/Users/bryce/Work/VESA-189/sample.parquet").ValueOrDie();
+  std::unique_ptr<parquet::arrow::FileReader> arrow_reader;
+  EXIT_NOT_OK(arrow::OpenFile(pq_file, ::arrow::default_memory_pool(), &arrow_reader));
+
+  std::shared_ptr<::arrow::Table> table;
+  EXIT_NOT_OK(arrow_reader->ReadTable(&table));
+  //
+
+  std::shared_ptr<WriterProperties> props = default_writer_properties();
+  std::shared_ptr<ArrowWriterProperties> arrow_props =
+      ArrowWriterProperties::Builder().set_use_threads(state.range(0))->build();
+
+  auto batches = ::arrow::TableBatchReader(table).ToRecordBatches().ValueOrDie();
+
+  // Track total bytes written by measuring the output stream
+  int64_t total_bytes = 0;
+
+  while (state.KeepRunning()) {
+    auto output = CreateOutputStream();
+    auto writer = parquet::arrow::FileWriter::Open(*table->schema().get(),
+                                                   ::arrow::default_memory_pool(), output,
+                                                   props, arrow_props)
+                      .ValueOrDie();
+
+    for (auto batch : batches) {
+      EXIT_NOT_OK(writer->WriteRecordBatch(*batch));
+    }
+
+    auto final_buf = output->Finish().ValueOrDie();
+    total_bytes += final_buf->size();
+  }
+
+  state.SetItemsProcessed(table->num_rows() * state.iterations());
+  state.SetBytesProcessed(total_bytes);
+}
+
+BENCHMARK(BM_WriteBinaryColumnMultithreaded)
+    ->ArgNames({"use_threads", "unique_values"})
+    // We vary unique values to trigger the dictionary-encoded (for low-cardinality)
+    // and plain (for high-cardinality) code paths.
+    ->Args({false})
+    ->Args({true});
+
 template <typename T>
 struct Examples {
   static constexpr std::array<T, 2> values() { return {127, 128}; }