code: private List<Row> getRows(String tableName, String columnName, Integer id)
     {
        List<Row> result;
        List<Row> table = m_tables.get(tableName);
        if (table == null)
        {
           result = Collections.<Row> emptyList();
        }
        else
        {
           if (columnName == null)
           {
              result = table;
           }
           else
           {
              result = new LinkedList<Row>();
              for (Row row : table)
              {
                 if (NumberHelper.equals(id, row.getInteger(columnName)))
                 {
                    result.add(row);
                 }
              }
           }
        }
        return result;
     }
docs: Filters a list of rows from the named table. If a column name and a value
  are supplied, then use this to filter the rows. If no column name is
  supplied, then return all rows.
  
  @param tableName table name
  @param columnName filter column name
  @param id filter column value
  @return filtered list of rows