fixed mvcc hints bug

mvcc/record.hpp

@@ -92,6 +92,12 @@ public:
     template <class U>
     bool committed(U& hints, const Id& id, const tx::Transaction& t)
     {
+        // you certainly can't see the transaction with id greater than yours
+        // as that means it started after this transaction and if it committed,
+        // it committed after this transaction had started.
+        if(id > t.id)
+            return false;
+
         auto hint_bits = hints.load();
 
         // if hints are set, return if xid is committed

mvcc/version_list.hpp

@@ -17,6 +17,7 @@ class VersionList : public LazyGC<VersionList<T>>
 
 public:
     using uptr = std::unique_ptr<VersionList<T>>;
+    using item_t = T;
 
     class Accessor
     {
@@ -72,7 +73,7 @@ public:
 
         const Id& id() const
         {
-            return vlist.identifier;
+            return vlist.id;
         }
 
     private:
@@ -80,14 +81,14 @@ public:
         VersionList<T>& vlist;
     };
 
-    VersionList() = default;
+    VersionList(Id id) : id(id) {}
     VersionList(const VersionList&) = delete;
 
     /* @brief Move constructs the version list
      * Note: use only at the beginning of the "other's" lifecycle since this
      * constructor doesn't move the RecordLock, but only the head pointer
      */
-    VersionList(VersionList&& other)
+    VersionList(VersionList&& other) : id(other.id)
     {
         this->head = other.head.load();
         this->identifier = other.id();
@@ -130,22 +131,12 @@ public:
 
     }
 
-    const Id& id() const
-    {
-        return identifier;
-    }
-
-    void id(const Id& identifier)
-    {
-        this->identifier = identifier;
-    }
+    const Id id;
 
 private:
     std::atomic<T*> head {nullptr};
     RecordLock lock;
 
-    Id identifier;
-
     //static Recycler recycler;
 
     T* find(const tx::Transaction& t)
@@ -172,8 +163,6 @@ private:
     {
         assert(head == nullptr);
 
-        // this->id = id;
-
         // create a first version of the record
         // TODO replace 'new' with something better
         auto v1 = new T();