Change LockFreeArray::FindValid from O(n) to O(1).

Author: mbutrovich

src/common/container/lock_free_array.cpp

@@ -73,23 +73,18 @@ ValueType LOCK_FREE_ARRAY_TYPE::FindValid(
     const std::size_t &offset, const ValueType &invalid_value) const {
   LOG_TRACE("Find Valid at %lu", offset);
 
-  std::size_t valid_array_itr = 0;
-  std::size_t array_itr;
-  auto lock_free_array_offset = lock_free_array.size();
-  for (array_itr = 0; array_itr < lock_free_array_offset; array_itr++) {
-    auto value = lock_free_array.at(array_itr);
-    if (value != invalid_value) {
-      // Check offset
-      if (valid_array_itr == offset) {
-        return value;
-      }
-
-      // Update valid value count
-      valid_array_itr++;
-    }
+  ValueType value = invalid_value;
+  if ((lock_free_array.size() > offset)) {
+    value = lock_free_array.at(offset);
+  } else {
+    return invalid_value;
+  }
+  
+  if (value != invalid_value)
+    return value;
+  else {
+    return invalid_value;
   }
-
-  return invalid_value;
 }
 
 template <typename ValueType>

src/concurrency/transaction_context.cpp

@@ -95,10 +95,11 @@ RWType TransactionContext::GetRWType(const ItemPointer &location) {
 void TransactionContext::RecordRead(const ItemPointer &location) {
   PELOTON_ASSERT(rw_set_.count(location) == 0 ||
       (rw_set_[location] != RWType::DELETE && rw_set_[location] != RWType::INS_DEL));
-
-  if (rw_set_.count(location) == 0) {
-    rw_set_[location] = RWType::READ;
+  auto rw_set_it = rw_set_.find(location);
+  if (rw_set_it != rw_set_.end()) {
+    return;
   }
+  rw_set_[location] = RWType::READ;
 }
 
 void TransactionContext::RecordReadOwn(const ItemPointer &location) {

src/storage/data_table.cpp

@@ -1002,7 +1002,7 @@ std::shared_ptr<storage::TileGroup> DataTable::GetTileGroup(
   PELOTON_ASSERT(tile_group_offset < GetTileGroupCount());
 
   auto tile_group_id =
-      tile_groups_.Find(tile_group_offset);
+      tile_groups_.FindValid(tile_group_offset, invalid_tile_group_id);
 
   return GetTileGroupById(tile_group_id);
 }