title: will mysql5.6 sql statement with limit will use all included partitions
body: <p>My table with 4 partitions, and there is a sql statement with 'limit 10' syntax.</p>
  <p>Use explain statement shows 4 partitions will be used.</p>
  <p>And I want to know, in this situation, if the partition0 match the query result 'limit 10', will it continues to search from other partitions?</p>
  <p>Or is it first to union 4 partitions and then get the matched 10 results。</p>
  <p>If yes, it means that the sql with limit syntax will be the same to the table without partitions,
  if the where clause include all data in the table?</p>