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MySQL /G 输出

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MySQL /G 输出

我运行了如下的 mysql 查询

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？行越少，查询速度越快？

答案1

这MySQL 参考手册说：

从 MySQL 5.1.28 开始，EXPLAIN PARTITIONS 输出的行列始终显示表中的记录总数。以前，这是匹配行的数量。（Bug#35745）

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