MySQL大数据表程度分区优化的细致步骤【MySQL教程】,mysql

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将运转中的大表修正成分区表

本文章代码仅限于以数据时候按月程度分区，其他需求可自行修正代码完成

1. 建立一张分区表

这张表的表字段和原表的字段一摸一样，附带分区

CREATE TABLE `metric_data_tmp`  (
    id bigint primary key auto_increment,
    metric varchar(128),
    datadt datetime not null unqine,
    value decimal(30, 6)
) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=utf8
partition by range (to_days(DATADT)) (
    PARTITION p201811 VALUES LESS THAN (to_days("2018-12-01")),
    PARTITION p201812 VALUES LESS THAN (to_days("2019-01-01")),
    PARTITION p201901 VALUES LESS THAN (to_days("2019-02-01")),
    PARTITION p201902 VALUES LESS THAN (to_days("2019-03-01")),
);

2. 将原表数据复制到暂时表

• 直接经由历程insert语句

insert into metric_data_tmp select * from metric_data;

• 数据量非常大，可运用select into outfile, Load data file体式格局导出导入

SELECT * INTO OUTFILE 'data.txt' FIELDS TERMINATED BY ',' FROM metric_data;
LOAD DATA INFILE 'data.txt' INTO TABLE metric_data_tmp FIELDS TERMINATED BY ',';

3. 重命名分区表和汗青表：

rename table metric_data to metric_data_bak;
rename table metric_data_tmp to metric_data;

4. 经由历程数据库的定时使命定时自动建立下月的分区

• 存储历程

delimiter $$
use `db_orbit`$$
drop procedure if exists `create_partition_by_month`$$
create procedure `create_partition_by_month`(in_schemaname varchar(64), in_tablename varchar(64))
begin
    # 用于推断须要建立的表分区是不是已存在
    declare rows_cnt int unsigned;
    # 要建立表分区的时候
    declare target_date timestamp;
    #分区的称号，花样为p201811
    declare partition_name varchar(8);
        
    #要建立的分区时候为下个月
    set target_date = date_add(now(), interval 1 month);
    set partition_name = date_format( target_date, 'p%Y%m' );
        
    # 推断要建立的分区是不是存在
    select count(1) into rows_cnt from information_schema.partitions t where table_schema = in_schemaname and table_name = in_tablename and ifnull(t.partition_name, '') = partition_name;
    if rows_cnt = 0 then
        set @sql = concat(
            'alter table `', 
            in_schemaname, 
            '`.`', 
            in_tablename, 
            '`',
            ' add partition (partition ', 
            partition_name, 
            " values less than (to_days('",
            date_format(DATE_ADD(target_date, INTERVAL 1 month), '%Y-%m-01'), 
            "')) engine = innodb);" 
        );
        prepare stmt from @sql;
        execute stmt;
        deallocate prepare stmt;
     else
       select concat("partition `", partition_name, "` for table `",in_schemaname, ".", in_tablename, "` already exists") as result;
     end if;
end$$
delimiter ;

• 建立定时使命，定时实行存储历程建立分区

DELIMITER $$
#该表地点的数据库称号
USE `db_orbit`$$
CREATE EVENT IF NOT EXISTS `generate_partition_for_metric_data`
ON SCHEDULE EVERY 1 MONTH   #实行周期，另有天、月等等
STARTS '2019-03-15 00:00:00'
ON COMPLETION PRESERVE
ENABLE
COMMENT 'Creating partitions'
DO BEGIN
    #挪用适才建立的存储历程，第一个参数是数据库称号，第二个参数是表称号
    CALL db_orbit.create_partition_by_month('db_orbit', 'metric_data');
END$$
DELIMITER ;

5.其他

• 查看表分区状况的SQL

select 
    partition_name part,  
    partition_expression expr, 
    partition_description descr, 
    table_rows  
from information_schema.partitions where table_name='metric_data';

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