HPCC-11138 - Fix TopN binaryInsert regression

Introduced regression in way new binaryInsert was used.
Removing last row, didn't reduce row count and left NULL row in
place. Change so that binaryInsert, optionally drops last row.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>

thorlcr/activities/topn/thtopnslave.cpp

@@ -130,10 +130,7 @@ public:
             {
                 const void *lastRow = sortedRows.query(topNLimit-1);
                 if (compare->docompare(lastRow, row) > 0)
-                {
-                    sortedRows.binaryInsert(row.getClear(), *compare);
-                    OwnedConstThorRow rowToDelete = sortedRows.getClear(topNLimit); // Nth+1, fall out now free.
-                }
+                    sortedRows.binaryInsert(row.getClear(), *compare, true);
                 else // had enough and out of range
                     ;
             }

thorlcr/thorutil/thmem.cpp

@@ -735,7 +735,7 @@ bool CThorExpandingRowArray::appendRows(CThorSpillableRowArray &inRows, bool tak
     return true;
 }
 
-bool CThorExpandingRowArray::binaryInsert(const void *row, ICompare &compare)
+bool CThorExpandingRowArray::binaryInsert(const void *row, ICompare &compare, bool dropLast)
 {
     dbgassertex(NULL != row);
     if (numRows >= maxRows)
@@ -743,7 +743,15 @@ bool CThorExpandingRowArray::binaryInsert(const void *row, ICompare &compare)
         if (!ensure(numRows+1))
             return false;
     }
-    binary_vec_insert_stable(row, rows, numRows++, compare); // takes ownership of row
+    binary_vec_insert_stable(row, rows, numRows, compare); // takes ownership of row
+    if (dropLast)
+    {
+    	// last row falls out, i.e. release last row and don't increment numRows
+    	dbgassertex(numRows); // numRows must be >=1 for dropLast
+    	ReleaseThorRow(rows[numRows]);
+    }
+    else
+    	++numRows;
     return true;
 }
 

thorlcr/thorutil/thmem.hpp

@@ -317,7 +317,7 @@ public:
         rows[numRows++] = row;
         return true;
     }
-    bool binaryInsert(const void *row, ICompare &compare); // NB: takes ownership on success
+    bool binaryInsert(const void *row, ICompare &compare, bool dropLast=false); // NB: takes ownership on success
     inline const void *query(rowidx_t i) const
     {
         if (i>=numRows)