Use a single Iterator instance for Cuckoohash

Author: poojanilangekar

src/concurrency/timestamp_ordering_transaction_manager.cpp

@@ -775,20 +775,19 @@ ResultType TimestampOrderingTransactionManager::CommitTransaction(
     gc_object_set->emplace_back(database_oid, table_oid, index_oid);
   }
 
+  // Call the GetIterator() function to explicitly lock the cuckoohash
+  // and initilaize the iterator
+  auto rw_set_lt = rw_set.GetConstIterator();
+
   oid_t database_id = 0;
   if (static_cast<StatsType>(settings::SettingsManager::GetInt(settings::SettingId::stats_mode)) !=
       StatsType::INVALID) {
     if (!rw_set.IsEmpty()) {
-      auto rw_set_iterator = rw_set.GetConstIterator();
-      const auto tile_group_id = rw_set_iterator.begin()->first.block;
+      const auto tile_group_id = rw_set_lt.begin()->first.block;
       database_id = manager.GetTileGroup(tile_group_id)->GetDatabaseId();
     }
   }
 
-  // Call the GetIterator() function to explicitly lock the cuckoohash
-  // and initilaize the iterator
-  auto rw_set_lt = rw_set.GetConstIterator();
-
   // install everything.
   // 1. install a new version for update operations;
   // 2. install an empty version for delete operations;
@@ -952,20 +951,20 @@ ResultType TimestampOrderingTransactionManager::AbortTransaction(
     gc_object_set->emplace_back(database_oid, table_oid, index_oid);
   }
 
+
+  // Call the GetIterator() function to explicitly lock the cuckoohash
+  // and initilaize the iterator
+  auto rw_set_lt = rw_set.GetConstIterator();
+
   oid_t database_id = 0;
   if (static_cast<StatsType>(settings::SettingsManager::GetInt(settings::SettingId::stats_mode)) !=
       StatsType::INVALID) {
     if (!rw_set.IsEmpty()) {
-      auto rw_set_iterator = rw_set.GetConstIterator();
-      const auto tile_group_id = rw_set_iterator.begin()->first.block;
+      const auto tile_group_id = rw_set_lt.begin()->first.block;
       database_id = manager.GetTileGroup(tile_group_id)->GetDatabaseId();
     }
   }
 
-  // Call the GetIterator() function to explicitly lock the cuckoohash
-  // and initilaize the iterator
-  auto rw_set_lt = rw_set.GetConstIterator();
-
   // Iterate through each item pointer in the read write set
   // TODO: This might be inefficient since we will have to get the
   // tile_group_header for each entry. Check if this needs to be consolidated