From 77b52a6a32ff96e2c99695c93d5d8567861bb379 Mon Sep 17 00:00:00 2001
From: Roman Nozdrin <drrtuy@gmail.com>
Date: Wed, 23 May 2018 22:31:21 +0300
Subject: [PATCH] MCOL-1446 CS sorting direction aligned with the server`s.

---
 dbcon/joblist/limitedorderby.cpp | 70 ++++++++++++++++++++++----------
 utils/rowgroup/rowgroup.h        |  9 +++-
 2 files changed, 57 insertions(+), 22 deletions(-)

diff --git a/dbcon/joblist/limitedorderby.cpp b/dbcon/joblist/limitedorderby.cpp
index 4f3366cc6..7da1accfe 100644
--- a/dbcon/joblist/limitedorderby.cpp
+++ b/dbcon/joblist/limitedorderby.cpp
@@ -171,15 +171,18 @@ void LimitedOrderBy::processRow(const rowgroup::Row& row)
     }
 }
 
-
+/*
+ * The f() copies top element from an ordered queue into a row group. It 
+ * does this backwards to syncronise sorting orientation with the server.
+ * The top row from the queue goes last into the returned set.
+ */ 
 void LimitedOrderBy::finalize()
 {
+    queue<RGData> tempQueue;
     if (fRowGroup.getRowCount() > 0)
         fDataQueue.push(fData);
 
-    // MCOL-1052 The removed check effectively disables sorting,
-    // since fStart = 0 if there is no OFFSET;
-    if (true)
+    if (fOrderByQueue.size() > 0)
     {
         uint64_t newSize = fRowsPerRG * fRowGroup.getRowSize();
         fMemSize += newSize;
@@ -190,27 +193,49 @@ void LimitedOrderBy::finalize()
                  << " @" << __FILE__ << ":" << __LINE__;
             throw IDBExcept(fErrorCode);
         }
-
+        
+        uint64_t offset = 0;
+        uint64_t i = 0;
+        list<RGData> tempRGDataList;
+        
+        // Skip first LIMIT rows in the the RowGroup
+        if ( fCount <= fOrderByQueue.size() )
+        {
+            offset = fCount % fRowsPerRG;
+            if(!offset && fCount > 0)
+                offset = fRowsPerRG;
+        }
+        else
+        {
+            offset = fOrderByQueue.size() % fRowsPerRG;
+            if(!offset && fOrderByQueue.size() > 0)
+                offset = fRowsPerRG;
+        }
+        
+        list<RGData>::iterator tempListIter = tempRGDataList.begin();
+        
+        i = 0;
+        uint32_t rSize = fRow0.getSize();
+        uint64_t preLastRowNumb = fRowsPerRG - 1;
         fData.reinit(fRowGroup, fRowsPerRG);
         fRowGroup.setData(&fData);
         fRowGroup.resetRowGroup(0);
-        fRowGroup.getRow(0, &fRow0);
-        queue<RGData> tempQueue;
-        uint64_t i = 0;
-
+        offset = offset != 0 ? offset - 1 : offset;
+        fRowGroup.getRow(offset, &fRow0);
+        
         while ((fOrderByQueue.size() > fStart) && (i++ < fCount))
         {
             const OrderByRow& topRow = fOrderByQueue.top();
             row1.setData(topRow.fData);
             copyRow(row1, &fRow0);
-            //memcpy(fRow0.getData(), topRow.fData, fRow0.getSize());
             fRowGroup.incRowCount();
-            fRow0.nextRow();
+            offset--;
+            fRow0.prevRow(rSize);
             fOrderByQueue.pop();
 
-            if (fRowGroup.getRowCount() >= fRowsPerRG)
+            if(offset == (uint64_t)-1)
             {
-                tempQueue.push(fData);
+                tempRGDataList.push_front(fData);
                 fMemSize += newSize;
 
                 if (!fRm->getMemory(newSize, fSessionMemLimit))
@@ -219,18 +244,21 @@ void LimitedOrderBy::finalize()
                          << " @" << __FILE__ << ":" << __LINE__;
                     throw IDBExcept(fErrorCode);
                 }
-
-                fData.reinit(fRowGroup, fRowsPerRG);
-                //fData.reset(new uint8_t[fRowGroup.getDataSize(fRowsPerRG)]);
+                
+                fData.reinit(fRowGroup, fRowsPerRG);            
                 fRowGroup.setData(&fData);
-                fRowGroup.resetRowGroup(0);
-                fRowGroup.getRow(0, &fRow0);
+                fRowGroup.resetRowGroup(0); // ?
+                fRowGroup.getRow(preLastRowNumb, &fRow0);
+                offset = preLastRowNumb;
             }
         }
-
+        // Push the last/only group into the queue.
         if (fRowGroup.getRowCount() > 0)
-            tempQueue.push(fData);
-
+            tempRGDataList.push_front(fData);   
+        
+        for(tempListIter = tempRGDataList.begin(); tempListIter != tempRGDataList.end(); tempListIter++)        
+            tempQueue.push(*tempListIter);
+        
         fDataQueue = tempQueue;
     }
 }
diff --git a/utils/rowgroup/rowgroup.h b/utils/rowgroup/rowgroup.h
index 896da1f4a..f1fc39dcc 100644
--- a/utils/rowgroup/rowgroup.h
+++ b/utils/rowgroup/rowgroup.h
@@ -355,7 +355,8 @@ public:
     */
     template<int len> void setUintField_offset(uint64_t val, uint32_t offset);
     inline void nextRow(uint32_t size);
-
+    inline void prevRow(uint32_t size, uint64_t number);
+    
     inline void setUintField(uint64_t val, uint32_t colIndex);
     template<int len> void setIntField(int64_t, uint32_t colIndex);
     inline void setIntField(int64_t, uint32_t colIndex);
@@ -896,6 +897,12 @@ inline void Row::nextRow(uint32_t size)
     data += size;
 }
 
+
+inline void Row::prevRow(uint32_t size, uint64_t number = 1)
+{
+    data -= size * number;
+}
+
 template<int len>
 inline void Row::setUintField(uint64_t val, uint32_t colIndex)
 {