mysql数据库分区及测试

1、 测试数据库是否支持分区

mysql可以通过下面语句判断是否支持分区：

SHOW VARIABLES LIKE '%partition%';

如果输出：have_partitioning   YES 表示支持分区。

或者通过：SHOW PLUGINS;

显示所有插件，如果有partition ACTIVE STORAGE ENGINE GPL 插件则表明支持分区

2、 创建测试表格

3、 将原表格数据复制到测试的表格

Insert into table_test select * from table

4、 对测试表格进行分区

alter table ta_monitor _history_test partition by RANGE (to_days(monitor_time))  

(PARTITION p0 VALUES LESS THAN (to_days('2018-01-01')), 

PARTITION p1 VALUES LESS THAN (to_days('2018-03-01')) , PARTITION p2 VALUES LESS THAN (to_days('2018-05-01')) , 

PARTITION p3 VALUES LESS THAN (to_days('2018-06-01')) , PARTITION p4 VALUES LESS THAN (to_days('2018-07-01')) , 

PARTITION p5 VALUES LESS THAN (to_days('2018-08-01')) , PARTITION p6 VALUES LESS THAN (to_days('2018-09-01')) , 

PARTITION p7 VALUES LESS THAN (to_days('2018-10-01')) , PARTITION p8 VALUES LESS THAN (to_days('2018-11-01')) , 

PARTITION p9 VALUES LESS THAN (to_days('2018-12-01')) , PARTITION p10 VALUES LESS THAN (to_days('2019-01-01')), 

PARTITION p11 VALUES LESS THAN (to_days('2019-02-01')), PARTITION P12 VALUES LESS THAN (to_days('2019-03-01')),

PARTITION P13 VALUES LESS THAN (to_days('2019-04-01')), PARTITION P14 VALUES LESS THAN (to_days('2019-05-01')),

PARTITION P15 VALUES LESS THAN (to_days('2019-06-01')), PARTITION P16 VALUES LESS THAN (to_days('2019-07-01')),

PARTITION P17 VALUES LESS THAN (to_days('2019-08-01')), PARTITION P18 VALUES LESS THAN (to_days('2019-09-01')),

PARTITION P19 VALUES LESS THAN (to_days('2019-10-01')), PARTITION P20 VALUES LESS THAN (to_days('2019-11-01')),

PARTITION P21 VALUES LESS THAN (to_days('2019-12-01')), PARTITION P22 VALUES LESS THAN (to_days('2020-01-01')),

PARTITION P23 VALUES LESS THAN (to_days('2020-02-01')), PARTITION P24 VALUES LESS THAN (to_days('2020-03-01')),

PARTITION P25 VALUES LESS THAN MAXVALUE );

5、 查看分区

SELECT
partition_name part,
partition_expression expr,
partition_description descr,
table_rows
FROM information_schema.partitions WHERE
table_schema = SCHEMA()
AND table_name='ta_monitor_parameter_history';

6、 测试分区

EXPLAIN SELECT

  *

FROM

  `ta_monitor _history`

WHERE monitor_time > '2018-07-01 01:00:00'

  AND monitor_time< '2018-07-19 00:00:00';

 

  EXPLAIN SELECT

  *

FROM

  `ta_monitorr_history_test`

WHERE monitor_time > '2018-07-01 01:00:00'

  AND monitor_time< '2018-07-19 00:00:00';

 

Rows显示遍历了多少行。

 

 

7、 重新定义range分区表:

Alter table emp partitionbyrange(salary)

(partition p1 values less than (2000),

partition p2 values less than (4000)); ----不会丢失数据

8、删除表的所有分区:

Alter table emp removepartitioning;--不会丢失数据

9、可以查看创建分区表的create语句

show create table 表名

10、增加分区

ALTER TABLE ta_monitor_parameter_history
ADD PARTITION (PARTITION p20200401 VALUES LESS THAN (TO_DAYS('2020-04-01')));

可能出现的问题：

a、如果创建分区表时，使用了MAXVALUE，形如：

PARTITION pmax VALUES LESS MAXVALUE，那么新增分区时会报错，类似如下：

MAXVALUE can only be used in last partition definition

解决办法：先删除最大分区，之后再添加

删除某一分区：ALTER TABLE  ta_monitor_parameter_history  DROP PARTITION p25;

 b、VALUES LESS THAN value must be strictly increasing for each partition（问题：添加的时间小于已经存在的最大时间）

根据   SELECT TO_DAYS('2019-01-01'); 查看距离1997年10月7号之间的天数。