Mysql 表分区

是否支持分区：
mysql> show variables like '%partition%';
+-----------------------+-------+
| Variable_name | Value |
+-----------------------+-------+
| have_partition_engine | YES |
+-----------------------+-------+
1 row in set (0.00 sec)

如果没有看到变量have_partition_engine的值为YES，那么MySQL的版本就不支持分区。

创建分区表：

 DELIMITER // 

create table VMMoniterData (
    id_ bigint not null AUTO_INCREMENT,
    vmid varchar(75) null,
    cpu varchar(75) null,
    memory varchar(75) null,
    bpsRead varchar(75) null,
    bpsWrite varchar(75) null,
    intranetRX0 varchar(75) null,
    intranetRX1 varchar(75) null,
    intranetWX0 varchar(75) null,
    intranetWX1 varchar(75) null,
    timeStamp datetime null,
    PRIMARY KEY (id_,timeStamp)
) engine InnoDB

PARTITION BY RANGE (TO_DAYS(timeStamp) ) (
    PARTITION p1 VALUES LESS THAN ( TO_DAYS('20161101') ),
    PARTITION p2 VALUES LESS THAN ( TO_DAYS('20161102') ),
    PARTITION p3 VALUES LESS THAN ( TO_DAYS('20161103') ),
    PARTITION p4 VALUES LESS THAN ( TO_DAYS('20161104') ),
    PARTITION p5 VALUES LESS THAN ( TO_DAYS('20161105') ),
    PARTITION p6 VALUES LESS THAN ( TO_DAYS('20161106') ),
    PARTITION p7 VALUES LESS THAN ( TO_DAYS('20161107') ),
    PARTITION p8 VALUES LESS THAN ( TO_DAYS('20161108') ),
    PARTITION p9 VALUES LESS THAN ( TO_DAYS('20161109') ),
    PARTITION p10 VALUES LESS THAN ( TO_DAYS('20161110') )
);

//
DELIMITER ;

添加分区表：

ALTER TABLE VMMoniterData ADD PARTITION(PARTITION p315 VALUES LESS THAN (TO_DAYS('22190527')));

查看表分区情况：

SELECT
  partition_name part, 
  partition_expression expr, 
  partition_description descr, 
  table_rows 
FROM
  INFORMATION_SCHEMA.partitions 
WHERE
  TABLE_SCHEMA = schema() 
  AND TABLE_NAME='VMMoniterData'; 

添加分区最大值

ALTER TABLE VMMoniterData ADD PARTITION (PARTITION p11 VALUES LESS THAN maxvalue);

删除分区

alter table VMMoniterData drop partition p0;

每天自动添加分区

合并分区：

ALTER TABLE test REORGANIZE PARTITION p20161101,p20161102 INTO (
    PARTITION p20161102 VALUES LESS THAN (TO_DAYS('20161102') )
);

拆分分区

ALTER TABLE test REORGANIZE PARTITION p20161102 INTO (
    PARTITION p20161101 VALUES LESS THAN (TO_DAYS('20161101')),
    PARTITION p20161102 VALUES LESS THAN (TO_DAYS('20161102'))
);

合并、拆分分区

 http://www.kubiji.cn/topic-id1558.html

mysql 碎片产生、mysql innodb碎片整理

注：随着数据库数据量的变大，如果要清除某个月的数据，用delete命令删除，mysql不会释放空间，必须整理碎片或者用修改引擎来重建表，才会释放空间，但是由于数据量很大，每次重建都得10-12小时的时间，太长了，想到了用mysql分区来解决这种弊病，通过删除分区，可以直接删除数据文件，那当然也可以释放空间。

分区的相关知识我就先不讲了，就说两点

1. 分区字段不要有空值，因为空值会默认到无用分区中，这样查询会多扫描分区。

2. 查询条件最好要带着分区字段，不然性能会很低，需要在所有分区里扫一遍。