Bug #1104

Fixed the bug where the sort order of transactions with equal timestamps
 was not stable, i.e. due to the lack of a total order, different merges
 produced different sortings and hence messed up transactions which
 have already been merged.

src/TDB2.cpp

@@ -1024,8 +1024,8 @@ void TDB2::merge (const std::string& mergeFile)
     mods.splice (mods.begin (), rmods);
 
     DEBUG_STR ("sorting taskmod list");
-    mods.sort ();
-    mods_history.sort ();
+    mods.sort (compareTaskmod);
+    mods_history.sort (compareTaskmod);
   }
   else if (rit == r.end ())
   {
@@ -1232,7 +1232,7 @@ void TDB2::merge (const std::string& mergeFile)
     // at this point undo contains the lines up to the branch-off point
     // now we merge mods (new modifications from mergefile)
     // with lmods (part of old undo.data)
-    lmods.sort();
+    lmods.sort(compareTaskmod);
     mods.merge (lmods);
     mods.merge (mods_history);
 

src/Taskmod.cpp

@@ -33,22 +33,38 @@
 #include <assert.h>
 #include <Taskmod.h>
 
+unsigned long Taskmod::curSequenceNumber = 0;
+
+bool compareTaskmod (Taskmod first, Taskmod second)
+{
+  if (first._timestamp == second._timestamp)
+  {
+    return first._sequenceNumber < second._sequenceNumber;
+  }
+  else
+  {
+    return first._timestamp < second._timestamp;
+  }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 Taskmod::Taskmod ()
 {
   _timestamp = 0;
   _bAfterSet = false;
   _bBeforeSet = false;
+  _sequenceNumber = curSequenceNumber++;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 Taskmod::Taskmod (const Taskmod& other)
 {
-  this->_before     = other._before;
-  this->_after      = other._after;
-  this->_timestamp  = other._timestamp;
-  this->_bAfterSet  = other._bAfterSet;
-  this->_bBeforeSet = other._bBeforeSet;
+  this->_before         = other._before;
+  this->_after          = other._after;
+  this->_timestamp      = other._timestamp;
+  this->_bAfterSet      = other._bAfterSet;
+  this->_bBeforeSet     = other._bBeforeSet;
+  this->_sequenceNumber = other._sequenceNumber;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -87,11 +103,12 @@ Taskmod& Taskmod::operator= (const Taskmod& other)
 {
   if (this != &other)
   {
-    this->_before     = other._before;
-    this->_after      = other._after;
-    this->_timestamp  = other._timestamp;
-    this->_bAfterSet  = other._bAfterSet;
-    this->_bBeforeSet = other._bBeforeSet;
+    this->_before         = other._before;
+    this->_after          = other._after;
+    this->_timestamp      = other._timestamp;
+    this->_bAfterSet      = other._bAfterSet;
+    this->_bBeforeSet     = other._bBeforeSet;
+	 this->_sequenceNumber = other._sequenceNumber;
   }
 
   return *this;
@@ -100,9 +117,10 @@ Taskmod& Taskmod::operator= (const Taskmod& other)
 ////////////////////////////////////////////////////////////////////////////////
 void Taskmod::reset (long timestamp)
 {
-  this->_bAfterSet  = false;
-  this->_bBeforeSet = false;
-  this->_timestamp  = timestamp;
+  this->_bAfterSet      = false;
+  this->_bBeforeSet     = false;
+  this->_timestamp      = timestamp;
+  this->_sequenceNumber = curSequenceNumber++;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -177,6 +195,12 @@ void Taskmod::setTimestamp (long timestamp)
   this->_timestamp = timestamp;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+void Taskmod::incSequenceNumber ()
+{
+  this->_sequenceNumber++;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 Task& Taskmod::getAfter ()
 {
@@ -195,6 +219,12 @@ long Taskmod::getTimestamp () const
   return _timestamp;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+unsigned long Taskmod::getSequenceNumber () const
+{
+  return _sequenceNumber;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 std::string Taskmod::getTimeStr () const
 {

src/Taskmod.h

@@ -33,6 +33,8 @@
 #include <Task.h>
 
 class Taskmod {
+  friend bool compareTaskmod (Taskmod first, Taskmod second);
+
 public:
   Taskmod ();
   Taskmod (const Taskmod& other);
@@ -59,11 +61,13 @@ public:
   void setAfter (const Task& after);
   void setBefore (const Task& before);
   void setTimestamp (long timestamp);
+  void incSequenceNumber ();
 
   // getter
   Task& getAfter ();
   Task& getBefore ();
   long getTimestamp () const;
+  unsigned long getSequenceNumber () const;
   std::string getTimeStr () const;
 
 protected:
@@ -72,7 +76,12 @@ protected:
   long _timestamp;
   bool _bAfterSet;
   bool _bBeforeSet;
+  unsigned long _sequenceNumber;
+
+  static unsigned long curSequenceNumber;
 };
 
+bool compareTaskmod (Taskmod first, Taskmod second);
+
 #endif