MyCat 枚举分片设计思考,查询命中条件

Mycat多租户实现的两种方式

MyCat,各种分片规则,仅保证插入的时候分片.表关联,join,查询怎么命中分片条件,还是需要设计.

今天稍微测了一下.

ER 分片,此方式,插入的时候能分片,但是查询的时候不是分片,可能使用其他分片规则,而且关联字段为 主键,也许可以设计出命中规则,但是我们需求是,可横向扩展,而且可控分片

<table name="orderinfo" primaryKey="ID" dataNode="dn1,dn2,dn3" rule="sharding-by-intfile">
    <childTable name="detail" primaryKey="ID"  joinKey="orderNo" parentKey="orderNo"/>
</table>

枚举分片,解决查询分片命中问题
mysql> explain select * from order a left join detail b on a.id = b.orderId where a.sharding_id = 0;
+-----------+----------------------------------------------------------------------------------------------------------------------+
| DATA_NODE | SQL                                                                                                                  |
+-----------+----------------------------------------------------------------------------------------------------------------------+
| dn1       | select * from order a left join detail b on a.id = b.orderId where a.sharding_id = 0 |
+-----------+----------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
两个表,都有枚举分片字段
mysql> explain select * from order a left detail  b on a.id = b.orderId where a.sharding_id and b.sharding_id = 0;
+-----------+----------------------------------------------------------------------------------------------------------------------------------------+
| DATA_NODE | SQL                                                                                                                                    |
+-----------+----------------------------------------------------------------------------------------------------------------------------------------+
| dn1       | select * from order a left detail  b on a.id = b.orderId where a.sharding_id and b.sharding_id = 0 |
+-----------+----------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> 

没有命中条件,造成全盘扫描

mysql> explain select * from order a left join detail b on a.id = b.orderId;
+-----------+----------------------------------------------------------------------------------------------+
| DATA_NODE | SQL                                                                                          |
+-----------+----------------------------------------------------------------------------------------------+
| dn1       | select * from rder a left join detail b on a.id = b.orderId |
| dn2       |  select * from rder a left join detail b on a.id = b.orderId |
| dn3       |  select * from rder a left join detail b on a.id = b.orderId |
+-----------+----------------------------------------------------------------------------------------------+
3 rows in set (0.00 sec)


UPDATE

Database changed
mysql> explain update detail set itemNum='100' where id = 8079
    -> ;
+-----------+--------------------------------------------------------------+
| DATA_NODE | SQL                                                          |
+-----------+--------------------------------------------------------------+
| dn1       |  update detail set itemNum='100' where id = 8079 |
| dn2       |  update detail set itemNum='100' where id = 8079 |
| dn3       |  update detail set itemNum='100' where id = 8079 |
+-----------+--------------------------------------------------------------+
3 rows in set (0.02 sec)

分片字段不能被更新
mysql> explain update detail set itemNum='100',shardingId=0  where id = 8079;
ERROR 1064 (HY000): Sharding column can't be updated DETAIL->SHARDINGID

加上分片字段

mysql> explain update order set itemNum='100' where id = 8079 and shardingId = 0;
+-----------+---------------------------------------------------------------------------------+
| DATA_NODE | SQL                                                                             |
+-----------+---------------------------------------------------------------------------------+
| dn1       | update order set itemNum='100' where id = 8079 and shardingId = 0 |
+-----------+---------------------------------------------------------------------------------+
1 row in set (0.00 sec)


删除,同样全盘扫描
mysql> explain delete detail where id = 8079;
+-----------+--------------------------------------------+
| DATA_NODE | SQL                                        |
+-----------+--------------------------------------------+
| dn1       | delete detail where id = 8079 |
| dn2       | delete detail where id = 8079 |
| dn3       | delete detail where id = 8079 |
+-----------+--------------------------------------------+
3 rows in set (0.00 sec)

强制命中条件
mysql> explain delete detail where id = 8079 and shardingId = 0;
+-----------+---------------------------------------------------------------+
| DATA_NODE | SQL                                                           |
+-----------+---------------------------------------------------------------+
| dn1       | delete detail where id = 8079 and shardingId = 0 |
+-----------+---------------------------------------------------------------+
1 row in set (0.00 sec)

全局表与分配表 inner join 以及 left jion right jion 都可以命中枚举
mysql> explain select * from user a inner join order b where a.id=b.userId and b.shardingId = 0;
+-----------+----------------------------------------------------------------------------------------------------------+
| DATA_NODE | SQL                                                                                                      |
+-----------+----------------------------------------------------------------------------------------------------------+
| dn1       | select * from user a inner join order b where a.id=b.userId and b.shardingId = 0|
+-----------+----------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> explain select * from user a right join order b on a.id =  b.userId where b.shardingId = 0;
+-----------+------------------------------------------------------------------------------------------------------------+
| DATA_NODE | SQL                                                                                                        |
+-----------+------------------------------------------------------------------------------------------------------------+
| dn1       |select * from user a right join order b on a.id =  b.userId where b.shardingId = 0|
+-----------+------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)