code: Map<String, byte[]> getRowKeyValue(List<IndexExpression> expressions, String primaryKeyName)
      {
          Map<String, byte[]> rowKeys = new HashMap<String, byte[]>();
  
          List<IndexExpression> rowExpressions = new ArrayList<IndexExpression>();
  
          if (expressions != null)
          {
              for (IndexExpression e : expressions)
              {
                  if (primaryKeyName.equals(new String(e.getColumn_name())))
                  {
                      IndexOperator operator = e.op;
                      if (operator.equals(IndexOperator.LTE) || operator.equals(IndexOperator.LT))
                      {
                          rowKeys.put(MAX_, e.getValue());
                          rowExpressions.add(e);
                      }
                      else if (operator.equals(IndexOperator.GTE) || operator.equals(IndexOperator.GT))
                      {
                          rowKeys.put(MIN_, e.getValue());
                          rowExpressions.add(e);
                      }
                      else if (operator.equals(IndexOperator.EQ))
                      {
                          rowKeys.put(MAX_, e.getValue());
                          rowKeys.put(MIN_, e.getValue());
                          rowExpressions.add(e);
                      }
                  }
              }
              expressions.removeAll(rowExpressions);
          }
          return rowKeys;
      }
docs: Returns list of row keys. First element will be min value and second will
  be major value.
  
  @param expressions the expressions
  @param primaryKeyName the primary key name
  @return the row key value