mysql按月表分区 MySQL分区表实现按月份归类
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MySQL单表数据量,建议不要超过2000W行,否则会对性能有较大影响。最近接手了一个项目,单表数据超7000W行,一条简单的查询语句等了50多分钟都没出结果,实在是难受,最终,我们决定用分区表。
建表
一般的表(innodb)创建后只有一个 idb 文件:
create table normal_table(id int primary key, no int)
查看数据库文件:
normal_table.ibd
创建按月份分区的分区表,注意!除了常规主键外,月份字段(用来分区的字段)也必须是主键:
create table partition_table(id int AUTO_INCREMENT, create_date date, name varchar(10), primary key(id, create_date)) ENGINE=INNODB DEFAULT CHARSET=utf8 partition by range(month(create_date))( partition quarter1 values less than(4), partition quarter2 values less than(7), partition quarter3 values less than(10), partition quarter4 values less than(13) );
查看数据库文件:
partition_table#p#quarter1.ibd partition_table#p#quarter2.ibd partition_table#p#quarter3.ibd partition_table#p#quarter4.ibd
插入
insert into partition_table(create_date, name) values("2021-01-25", "tom1"); insert into partition_table(create_date, name) values("2021-02-25", "tom2"); insert into partition_table(create_date, name) values("2021-03-25", "tom3"); insert into partition_table(create_date, name) values("2021-04-25", "tom4"); insert into partition_table(create_date, name) values("2021-05-25", "tom5"); insert into partition_table(create_date, name) values("2021-06-25", "tom6"); insert into partition_table(create_date, name) values("2021-07-25", "tom7"); insert into partition_table(create_date, name) values("2021-08-25", "tom8"); insert into partition_table(create_date, name) values("2021-09-25", "tom9"); insert into partition_table(create_date, name) values("2021-10-25", "tom10"); insert into partition_table(create_date, name) values("2021-11-25", "tom11"); insert into partition_table(create_date, name) values("2021-12-25", "tom12");
查询
select count(*) from partition_table; > 12 查询第二个分区(第二季度)的数据: select * from partition_table PARTITION(quarter2); 4 2021-04-25 tom4 5 2021-05-25 tom5 6 2021-06-25 tom6
删除
当删除表时,该表的所有分区文件都会被删除
补充:Mysql自动按月表分区
核心的两个存储过程:
- auto_create_partition为创建表分区,调用后为该表创建到下月结束的表分区。
- auto_del_partition为删除表分区,方便历史数据空间回收。
DELIMITER $$ DROP PROCEDURE IF EXISTS auto_create_partition$$ CREATE PROCEDURE `auto_create_partition`(IN `table_name` varchar(64)) BEGIN SET @next_month:=CONCAT(date_format(date_add(now(),interval 2 month),'%Y%m'),'01'); SET @SQL = CONCAT( 'ALTER TABLE `', table_name, '`', ' ADD PARTITION (PARTITION p', @next_month, " VALUES LESS THAN (TO_DAYS(", @next_month ,")) );" ); PREPARE STMT FROM @SQL; EXECUTE STMT; DEALLOCATE PREPARE STMT; END$$ DROP PROCEDURE IF EXISTS auto_del_partition$$ CREATE PROCEDURE `auto_del_partition`(IN `table_name` varchar(64),IN `reserved_month` int) BEGIN DECLARE v_finished INTEGER DEFAULT 0; DECLARE v_part_name varchar(100) DEFAULT ""; DECLARE part_cursor CURSOR FOR select partition_name from information_schema.partitions where table_schema = schema() and table_name=@table_name and partition_description < TO_DAYS(CONCAT(date_format(date_sub(now(),interval reserved_month month),'%Y%m'),'01')); DECLARE continue handler FOR NOT FOUND SET v_finished = TRUE; OPEN part_cursor; read_loop: LOOP FETCH part_cursor INTO v_part_name; if v_finished = 1 then leave read_loop; end if; SET @SQL = CONCAT( 'ALTER TABLE `', table_name, '` DROP PARTITION ', v_part_name, ";" ); PREPARE STMT FROM @SQL; EXECUTE STMT; DEALLOCATE PREPARE STMT; END LOOP; CLOSE part_cursor; END$$ DELIMITER ;
下面是示例
-- 假设有个表叫records,设置分区条件为按end_time按月分区 DROP TABLE IF EXISTS `records`; CREATE TABLE `records` ( `id` int(11) NOT NULL AUTO_INCREMENT, `start_time` datetime NOT NULL, `end_time` datetime NOT NULL, `memo` varchar(128) CHARACTER SET utf8mb4 NOT NULL, PRIMARY KEY (`id`,`end_time`) ) PARTITION BY RANGE (TO_DAYS(end_time))( PARTITION p20200801 VALUES LESS THAN ( TO_DAYS('20200801')) ); DROP EVENT IF EXISTS `records_auto_partition`; -- 创建一个Event,每月执行一次,同时最多保存6个月的数据 DELIMITER $$ CREATE EVENT `records_auto_partition` ON SCHEDULE EVERY 1 MONTH ON COMPLETION PRESERVE ENABLE DO BEGIN call auto_create_partition('records'); call auto_del_partition('records',6); END$$ DELIMITER ;
几点注意事项:
- 对于Mysql 5.1以上版本来说,表分区的索引字段必须是主键
- 存储过程中,DECLARE 必须紧跟着BEGIN,否则会报看不懂的错误
- 游标的DECLARE需要在定义声明之后,否则会报错
- 如果是自己安装的Mysql,有可能Event功能是未开启的,在创建Event时会提示错误;修改my.cnf,在 [mysqld] 下添加event_scheduler=1后重启即可。
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