我运行mysql查询如下
在非分区表上
mysql> use test31 Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Database changed mysql> explain partitions SELECT * FROM my_friends WHERE (requestor = '1234567890' OR contact = '1234567890') AND status = 1 ORDER BY request_id DESC LIMIT 0,100\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: my_friends partitions: NULL type: index_merge possible_keys: friend_index,requestor,contact key: friend_index,contact key_len: 17,17 ref: NULL rows: 2 Extra: Using sort_union(friend_index,contact); Using where; Using filesort 1 row in set (0.00 sec) 在分区表上
mysql> explain partitions SELECT * FROM my_friends WHERE (requestor = '1234567890' OR contact = '1234567890') AND status = 1 ORDER BY request_id DESC LIMIT 0,100\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: my_friends partitions: p1_p1sp0,p1_p1sp1,p1_p1sp2,p1_p1sp3,p1_p1sp4,p1_p1sp5,p1_p1sp6,p1_p1sp7,p1_p1sp8,p1_p1sp9,p1_p1sp10,p1_p1sp11,p1_p1sp12,p1_p1sp13,p1_p1sp14,p1_p1sp15,p1_p1sp16,p1_p1sp17,p1_p1sp18,p1_p1sp19,p1_p1sp20,p1_p1sp21,p1_p1sp22,p1_p1sp23,p1_p1sp24,p1_p1sp25,p1_p1sp26,p1_p1sp27,p1_p1sp28,p1_p1sp29 type: index_merge possible_keys: friend_index,requestor,contact key: friend_index,contact key_len: 17,17 ref: NULL rows: 60 Extra: Using sort_union(friend_index,contact); Using where; Using filesort 1 row in set (0.01 sec)
“行”是什么意思？ 更less的行是更快的查询？
MySQL参考手册说：
从MySQL 5.1.28开始，EXPLAIN PARTITIONS输出的rows列总是显示表中的logging总数。 以前，这是匹配行的数量。 （错误＃35745）