Fix null std::optional read issue

Author: alinaliBQ

cpp/src/arrow/flight/sql/odbc/flight_sql/flight_sql_stream_chunk_buffer.cc

@@ -59,37 +59,36 @@ FlightStreamChunkBuffer::FlightStreamChunkBuffer(
     util::ThrowIfNotOK(result.status());
     std::shared_ptr<FlightStreamReader> stream_reader_ptr(std::move(result.ValueOrDie()));
 
-    BlockingQueue<std::optional<
-        std::pair<Result<FlightStreamChunk>, std::shared_ptr<FlightSqlClient>>>>::Supplier
-        supplier = [=] {
-          auto result = stream_reader_ptr->Next();
-          bool is_not_ok = !result.ok();
-          bool is_not_empty = result.ok() && (result.ValueOrDie().data != nullptr);
-
-          // If result is valid, save the temp Flight SQL Client for future stream reader
-          // call. temp_flight_sql_client is intentionally null if the list of endpoint
-          // Locations is empty.
-          // After all data is fetched from reader, the temp client is closed.
-          if (is_not_ok || is_not_empty) {
-            return std::make_optional(
-                std::make_pair(std::move(result), temp_flight_sql_client));
-          } else {
-            return std::optional<
-                std::pair<Result<FlightStreamChunk>, std::shared_ptr<FlightSqlClient>>>{};
-          }
-        };
+    BlockingQueue<std::pair<Result<FlightStreamChunk>,
+                            std::shared_ptr<FlightSqlClient>>>::Supplier supplier = [=] {
+      auto result = stream_reader_ptr->Next();
+      bool is_not_ok = !result.ok();
+      bool is_not_empty = result.ok() && (result.ValueOrDie().data != nullptr);
+
+      // If result is valid, save the temp Flight SQL Client for future stream reader
+      // call. temp_flight_sql_client is intentionally null if the list of endpoint
+      // Locations is empty.
+      // After all data is fetched from reader, the temp client is closed.
+      if (is_not_ok || is_not_empty) {
+        return std::make_optional(
+            std::make_pair(std::move(result), temp_flight_sql_client));
+      } else {
+        return std::optional<
+            std::pair<Result<FlightStreamChunk>, std::shared_ptr<FlightSqlClient>>>{};
+      }
+    };
     queue_.AddProducer(std::move(supplier));
   }
 }
 
 bool FlightStreamChunkBuffer::GetNext(FlightStreamChunk* chunk) {
-  std::optional<std::pair<Result<FlightStreamChunk>, std::shared_ptr<FlightSqlClient>>>
+  std::pair<Result<FlightStreamChunk>, std::shared_ptr<FlightSqlClient>>
       closeable_endpoint_stream_pair;
   if (!queue_.Pop(&closeable_endpoint_stream_pair)) {
     return false;
   }
 
-  Result<FlightStreamChunk> result = closeable_endpoint_stream_pair.value().first;
+  Result<FlightStreamChunk> result = closeable_endpoint_stream_pair.first;
   if (!result.status().ok()) {
     Close();
     throw DriverException(result.status().message());

cpp/src/arrow/flight/sql/odbc/flight_sql/flight_sql_stream_chunk_buffer.h

@@ -31,8 +31,7 @@ using arrow::flight::sql::FlightSqlClient;
 using arrow::flight::sql::odbc::BlockingQueue;
 
 class FlightStreamChunkBuffer {
-  BlockingQueue<std::optional<
-      std::pair<Result<FlightStreamChunk>, std::shared_ptr<FlightSqlClient>>>>
+  BlockingQueue<std::pair<Result<FlightStreamChunk>, std::shared_ptr<FlightSqlClient>>>
       queue_;
 
  public:

cpp/src/arrow/flight/sql/odbc/odbcabstraction/include/odbcabstraction/blocking_queue.h

@@ -58,7 +58,7 @@ class BlockingQueue {
 
         // Only one thread at a time be notified and call supplier
         auto item = supplier();
-        if (!item) break;
+        if (!item.has_value()) break;
 
         Push(*item);
       }