write SwitchToSnapShot

storage/include/storage/disk_map.hpp

@@ -53,6 +53,20 @@ class DiskMap : public DataDriverBase {
     res.push_back({data_file_identifier, data_file_path, data_disk_manager});
     return res;
   }
+  void LockDownForCheckOut() override {
+    delete indexer;
+    delete index_bpm;
+    delete index_disk_manager;
+    delete data_storage;
+    delete data_bpm;
+    delete data_disk_manager;
+    indexer = nullptr;
+    index_bpm = nullptr;
+    index_disk_manager = nullptr;
+    data_storage = nullptr;
+    data_bpm = nullptr;
+    data_disk_manager = nullptr;
+  }
   Value Get(const Key &key) {
     size_t data_id;
     if ((data_id = indexer->Get(key)) == kInvalidValueIndex) throw std::runtime_error("Key not found");

storage/include/storage/driver.h

@@ -14,5 +14,6 @@ class DataDriverBase {
   virtual ~DataDriverBase() = default;
   virtual sjtu::vector<FileEntry> ListFiles() = 0;
   virtual void Flush() = 0;
+  virtual void LockDownForCheckOut() = 0;
 };
 #endif  // DRIVER_H