using forward_as_tuple in multiple keys based SMJ (#74)

Signed-off-by: Yuan Zhou <yuan.zhou@intel.com>

cpp/src/codegen/arrow_compute/ext/conditioned_merge_join_kernel.cc

@@ -219,12 +219,12 @@ class ConditionedMergeJoinKernel::Impl {
     auto left_tuple_name = left_paramater;
     auto right_tuple_name = right_paramater;
     if (project_output_list[0].size() > 1) {
-      function_define_ss << "auto left_tuple = std::make_tuple(" << left_paramater
+      function_define_ss << "auto left_tuple = std::forward_as_tuple(" << left_paramater
                          << " );" << std::endl;
       left_tuple_name = "left_tuple";
     }
     if (project_output_list[1].size() > 1) {
-      function_define_ss << "auto right_tuple = std::make_tuple(" << right_paramater
+      function_define_ss << "auto right_tuple = std::forward_as_tuple(" << right_paramater
                          << " );" << std::endl;
       right_tuple_name = "right_tuple";
     }
@@ -929,4 +929,4 @@ arrow::Status ConditionedMergeJoinKernel::DoCodeGen(
 }  // namespace extra
 }  // namespace arrowcompute
 }  // namespace codegen
-}  // namespace sparkcolumnarplugin
+}  // namespace sparkcolumnarplugin

cpp/src/codegen/arrow_compute/ext/merge_join_kernel.cc

@@ -1069,7 +1069,7 @@ class ConditionedJoinArraysKernel::Impl {
     std::stringstream ss;
     std::string tuple_str;
     if (multiple_cols) {
-      tuple_str = "std::make_tuple";
+      tuple_str = "std::forward_as_tuple";
     }
     if (multiple_cols) {
       for (int i = 0; i < size; i++) {
@@ -1115,7 +1115,7 @@ class ConditionedJoinArraysKernel::Impl {
         tuple_str += local_tuple;
       }
       tuple_str.erase(tuple_str.end() - 1, tuple_str.end());
-      ss << std::endl << "return {" + tuple_str + "};" << std::endl;
+      ss << std::endl << "return std::forward_as_tuple(" + tuple_str + ");" << std::endl;
     } else {
 
       ss << std::endl << "return it->GetView(segment_len);" << std::endl;