title: How mysql implement mysql_use_result?
body: <p>In my project, I would like to fetch millions of records into client, then I find the memory used in client side is pretty huge(about 1.5G+). Then I find using <code>SSCursor</code> of Mysql would decrease the memory that client use. 
  I have made an experiments using <code>SSCursor</code>, I found that the memory used by client is pretty small , and the memory used by server is also vary too much. So, I am curious how mysql implement <code>mysql_use_result</code>.</p>