mysql 的诡异现象，CPU 100%，order by 主键提示 sending data

mysql 单表数据量 50万，执行查询一直CPU爆表，按照hash(id) 分表 partitions 10份。
问题依旧出现，新问题出现了 select * from tb where status in(1,2) and type=1 order by id desc limit 1 提示sending data

诡异

MariaDB [db2_zz]> select count(tid) from zz_info where status in(1,2) and c2=12176;
+------------+
| count(tid) |
+------------+
|       4167 |
+------------+
1 row in set (0.01 sec)

MariaDB [db2_zz]> select max(uptime) from zz_info where status in(1,2) and c2=12176;
+-------------+
| max(uptime) |
+-------------+
|  1498126645 |
+-------------+
1 row in set (4.80 sec)

MariaDB [db2_zz]> select max(tid) from zz_info where status in (1,2) and c2=12176;
+----------+
| max(tid) |
+----------+
|  1364323 |
+----------+
1 row in set (0.00 sec)

MariaDB [db2_zz]> SELECT max(tid) FROM `zz_info` WHERE (`status` IN (1, 2)) AND (`d1`='25') LIMIT 1;
+----------+
| max(tid) |
+----------+
|  1636927 |
+----------+
1 row in set (1.59 sec)

字段status 和 d1 都有加单独索引，给 status d1 加复合索引之后，问题改善，但是一用上 order by 主键就不行，sending data。

MariaDB [db2_zz]>  SELECT max(id) FROM `zz_info` WHERE (`status` IN (1, 2)) AND (`d1`='25') LIMIT 1;
+----------+
| max(tid) |
+----------+
|  1636927 |
+----------+
1 row in set (0.11 sec)

猜想

mysql 分表 partition by hash(id) partitions 10 之后用主键排序性能更差，还不如使用索引来排序快，最后只能改为 select max(主键) 加上 符合索引来解决问题。

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