Edit mvcc read function

mvcc.py

@@ -9,11 +9,18 @@ class MVCC :
         return time.time()
 
     def setTimestampNow(self, key, timestamp, storage : strg) :
-        tempTimestamp = timestamp
-        storage.setdata[key]["timestamp"] = tempTimestamp
+        storage.setdata[key]["timestamp"] = timestamp
 
     def read(self, key, storage : strg) :
-        return storage.setdata[key]["value"]
+        tempTimestamp = self.getTimestampNow()
+        if (storage.setdata[key]["timestamp"] > tempTimestamp) :
+            # rollback transaction
+            
+            # reject operation
+            return False
+        else :
+            self.setTimestampNow(key, tempTimestamp, storage)
+            return True, storage.setdata[key]["value"]
     
     def write(self, key, value, storage : strg) :
         tempTimestamp = self.getTimestampNow()