MySQL普通表怎么转换成分区表
作者：若安舟已远
时间：2023-04-27
来源：互联网
浏览：0
版本:MySQL-5.7.32前言:对于业务繁忙的数据库来说，在运行了一定时间后，往往会产生一些数据量较大的表，特别是对于每天新增数据较多的日志表或者流水表，大表对于日常的运维非常的不方便，特别是数据的清理、迁移，表的访问性能也会随着数据量的增大而受到影响，因此，对于大表我们需要进行优化拆分，通常拆分的方案有所以，通常选择分区表改造方案的主要原因都是为了避免应用层面的改造，对应用层面透明，以及方便日常的运维，前提是表具备改造分区条件。改造分区前期条件:参考文档MySQL官方文档1根据业务的场景以及数据的分
版本:
MySQL-5.7.32
前言:
对于业务繁忙的数据库来说，在运行了一定时间后，往往会产生一些数据量较大的表，特别是对于每天新增数据较多的日志表或者流水表，大表对于日常的运维非常的不方便，特别是数据的清理、迁移，表的访问性能也会随着数据量的增大而受到影响，因此，对于大表我们需要进行优化拆分，通常拆分的方案有
所以，通常选择分区表改造方案的主要原因都是为了避免应用层面的改造，对应用层面透明，以及方便日常的运维，前提是表具备改造分区条件。
改造分区前期条件:
参考文档
MySQL官方文档
1 根据业务的场景以及数据的分布，确认是否有匹配的分区表类型以及分区列
对于日志表，流水表这种按日期类型进行操作的，可以选择进行range分区
对于按用户ID类型的进行操作的，可以选择进行hash，key分区
对于按渠道，类型的进行操作的，可以选择进行list分区
2 应用涉及的sql，需要90%以上的操作都包含分区列，按分区操作，如果sql没有包含分区条件，扫描全分区，性能会出现下降。
查询表sql操作历史
select db,query,exec_count from sys.x$statement_analysis where lower(query) like '%%'order by exec_count;
3 主键必须包含分区键
4 分区键表达式只支持部分函数，存储过程，不支持二级制操作符以及/
5 分区不支持外键
查询表外键
select * from information_schema.KEY_COLUMN_USAGE where constraint_schema ='' and REFERENCED_TABLE_SCHEMA is not null\G
6 不支持查询缓存
7 5.7版本单个表分区最大支持8192个，并且会话第一次访问分区表，都需要打开全部的分区表，所以避免建立过多的分区
8 数据库最大文件打开数open_files_limit要设置足够大以满足表，分区的打开数量
9 数据库大文件large_files_support设置为on
10 分区列支持null值(对于rang分区，null值总小于任何的一个非null值，即存放在最左边的分区;对于list分区需要显示指定null值条件)，但从数据管理以及规范来看，不建议分区列存放null值，并且如果表有主键，则分区列不能为null值，因为分区列需要作为主键的一部分，不能为null
12 MySQL目前没有自动分区功能，所以需要监控分区的使用情况，通过job自动或者定时手动添加新分区
13 确定数据保留期限，定期归档分区数据
分区改造案例:
以下是一张数据量为766万的大表xxxx_user. xxxx_tab,计划将其改造为范围分区，按月存放。
select table_schema,table_name,table_rows,data_length/1024/1024/1024 from information_schema.tables where table_name='xxxx_tab';
表结构
CREATE TABLE `xxxx_tab` ( `ROLE_SEQ` bigint(20) NOT NULL , `PRD_ID` varchar(64) NOT NULL , `MAKE_RIGHT` varchar(1) DEFAULT '0' , `CHECK_RIGHT` varchar(1) DEFAULT '0' , `AUTH_RIGHT` varchar(1) DEFAULT '0' , `AUTH_GROUP` varchar(4) DEFAULT NULL , `RELEASE_RIGHT` varchar(1) DEFAULT '0' , `CREATE_USER_SEQ` bigint(20) DEFAULT NULL , `CREATE_DEPT_SEQ` bigint(20) DEFAULT NULL , `CREATE_TIME` datetime DEFAULT NULL , `UPDATE_USER_SEQ` bigint(20) DEFAULT NULL , `UPDATE_DEPT_SEQ` bigint(20) DEFAULT NULL , `UPDATE_TIME` datetime DEFAULT NULL , PRIMARY KEY (`PRD_ID`,`ROLE_SEQ`), KEY `xxxx_tab_IDX01` (`ROLE_SEQ`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
分区列create_time日期最大值，最小值，根据这个范围按月创建分区
select max(CREATE_TIME),min(CREATE_TIME) from xxxx_tab;
分区列null值，对于存在的null值，需要应用对null数据进行处理，并且程序上需要确保数据写入not null
select count(*) from xxxx_tab where create_time is null;
主键重建添加分区列
alter table xxxx_tab drop primary key,add primary key (`PRD_ID`,`ROLE_SEQ`,`CREATE_TIME`);
由于主键没有包含分区列，需要重建主键添加分区列，对于主键重建我采取的是官方的online ddl功能，这种ddl操作会造成主从延时，但是不会产生大量的binlog，对于主从实时性要求高的，可以采用第三方的在线工具pt-osc,gh-ost
表转化为分区表
采用pt-osc在线将表转化为分区表，对于partition by 官方是不支持online ddl的，所以需要采用第三方的在线工具
./pt-online-schema-change --user=xxx --password=xxx --charset=utf8 D=xxxx_user,t=xxxx_tab --alter "PARTITION BY RANGE COLUMNS(CREATE_TIME)
(PARTITION p200001 VALUES LESS THAN ('2000-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p200101 VALUES LESS THAN ('2001-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p201707 VALUES LESS THAN ('2017-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p201708 VALUES LESS THAN ('2017-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p201709 VALUES LESS THAN ('2017-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p201710 VALUES LESS THAN ('2017-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p201711 VALUES LESS THAN ('2017-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p201712 VALUES LESS THAN ('2018-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p201801 VALUES LESS THAN ('2018-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p201802 VALUES LESS THAN ('2018-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p201803 VALUES LESS THAN ('2018-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p201804 VALUES LESS THAN ('2018-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p201805 VALUES LESS THAN ('2018-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p201806 VALUES LESS THAN ('2018-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p201807 VALUES LESS THAN ('2018-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p201808 VALUES LESS THAN ('2018-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p201809 VALUES LESS THAN ('2018-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p201810 VALUES LESS THAN ('2018-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p201811 VALUES LESS THAN ('2018-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p201812 VALUES LESS THAN ('2019-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p201901 VALUES LESS THAN ('2019-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p201902 VALUES LESS THAN ('2019-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p201903 VALUES LESS THAN ('2019-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p201904 VALUES LESS THAN ('2019-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p201905 VALUES LESS THAN ('2019-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p201906 VALUES LESS THAN ('2019-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p201907 VALUES LESS THAN ('2019-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p201908 VALUES LESS THAN ('2019-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p201909 VALUES LESS THAN ('2019-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p201910 VALUES LESS THAN ('2019-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p201911 VALUES LESS THAN ('2019-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p201912 VALUES LESS THAN ('2020-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p202001 VALUES LESS THAN ('2020-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p202002 VALUES LESS THAN ('2020-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p202003 VALUES LESS THAN ('2020-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p202004 VALUES LESS THAN ('2020-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p202005 VALUES LESS THAN ('2020-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p202006 VALUES LESS THAN ('2020-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p202007 VALUES LESS THAN ('2020-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p202008 VALUES LESS THAN ('2020-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p202009 VALUES LESS THAN ('2020-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p202010 VALUES LESS THAN ('2020-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p202011 VALUES LESS THAN ('2020-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p202012 VALUES LESS THAN ('2021-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p202101 VALUES LESS THAN ('2021-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p202102 VALUES LESS THAN ('2021-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p202103 VALUES LESS THAN ('2021-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p202104 VALUES LESS THAN ('2021-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p202105 VALUES LESS THAN ('2021-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p202106 VALUES LESS THAN ('2021-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p202107 VALUES LESS THAN ('2021-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p202108 VALUES LESS THAN ('2021-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p202109 VALUES LESS THAN ('2021-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p202110 VALUES LESS THAN ('2021-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p202111 VALUES LESS THAN ('2021-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p202112 VALUES LESS THAN ('2022-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p202201 VALUES LESS THAN ('2022-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p202202 VALUES LESS THAN ('2022-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p202203 VALUES LESS THAN ('2022-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p202204 VALUES LESS THAN ('2022-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p202205 VALUES LESS THAN ('2022-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p202206 VALUES LESS THAN ('2022-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p202207 VALUES LESS THAN ('2022-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p202208 VALUES LESS THAN ('2022-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p202209 VALUES LESS THAN ('2022-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p202210 VALUES LESS THAN ('2022-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p202211 VALUES LESS THAN ('2022-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p202212 VALUES LESS THAN ('2023-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p202301 VALUES LESS THAN ('2023-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p202302 VALUES LESS THAN ('2023-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p202303 VALUES LESS THAN ('2023-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p202304 VALUES LESS THAN ('2023-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p202305 VALUES LESS THAN ('2023-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p202306 VALUES LESS THAN ('2023-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p202307 VALUES LESS THAN ('2023-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p202308 VALUES LESS THAN ('2023-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p202309 VALUES LESS THAN ('2023-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p202310 VALUES LESS THAN ('2023-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p202311 VALUES LESS THAN ('2023-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p202312 VALUES LESS THAN ('2024-01-01 00:00:00') ENGINE = InnoDB,
PARTITION pmax VALUES LESS THAN (MAXVALUE) ENGINE = InnoDB)" --recursion-method hosts --max-lag 600 --nodrop-old-table --print --statistics --execute分区后表模型
CREATE TABLE `xxxx_tab` (
`ROLE_SEQ` bigint(20) NOT NULL ,
`PRD_ID` varchar(64) NOT NULL ,
`MAKE_RIGHT` varchar(1) DEFAULT '0' ,
`CHECK_RIGHT` varchar(1) DEFAULT '0' ,
`AUTH_RIGHT` varchar(1) DEFAULT '0' ,
`AUTH_GROUP` varchar(4) DEFAULT NULL ,
`RELEASE_RIGHT` varchar(1) DEFAULT '0' ,
`CREATE_USER_SEQ` bigint(20) DEFAULT NULL ,
`CREATE_DEPT_SEQ` bigint(20) DEFAULT NULL ,
`CREATE_TIME` datetime NOT NULL ,
`UPDATE_USER_SEQ` bigint(20) DEFAULT NULL ,
`UPDATE_DEPT_SEQ` bigint(20) DEFAULT NULL ,
`UPDATE_TIME` datetime DEFAULT NULL ,
PRIMARY KEY (`PRD_ID`,`ROLE_SEQ`,`CREATE_TIME`),
KEY `xxxx_tab_IDX01` (`ROLE_SEQ`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
PARTITION BY RANGE COLUMNS(CREATE_TIME)
(PARTITION p200001 VALUES LESS THAN ('2000-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p200101 VALUES LESS THAN ('2001-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p201707 VALUES LESS THAN ('2017-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p201708 VALUES LESS THAN ('2017-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p201709 VALUES LESS THAN ('2017-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p201710 VALUES LESS THAN ('2017-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p201711 VALUES LESS THAN ('2017-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p201712 VALUES LESS THAN ('2018-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p201801 VALUES LESS THAN ('2018-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p201802 VALUES LESS THAN ('2018-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p201803 VALUES LESS THAN ('2018-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p201804 VALUES LESS THAN ('2018-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p201805 VALUES LESS THAN ('2018-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p201806 VALUES LESS THAN ('2018-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p201807 VALUES LESS THAN ('2018-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p201808 VALUES LESS THAN ('2018-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p201809 VALUES LESS THAN ('2018-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p201810 VALUES LESS THAN ('2018-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p201811 VALUES LESS THAN ('2018-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p201812 VALUES LESS THAN ('2019-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p201901 VALUES LESS THAN ('2019-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p201902 VALUES LESS THAN ('2019-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p201903 VALUES LESS THAN ('2019-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p201904 VALUES LESS THAN ('2019-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p201905 VALUES LESS THAN ('2019-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p201906 VALUES LESS THAN ('2019-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p201907 VALUES LESS THAN ('2019-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p201908 VALUES LESS THAN ('2019-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p201909 VALUES LESS THAN ('2019-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p201910 VALUES LESS THAN ('2019-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p201911 VALUES LESS THAN ('2019-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p201912 VALUES LESS THAN ('2020-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p202001 VALUES LESS THAN ('2020-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p202002 VALUES LESS THAN ('2020-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p202003 VALUES LESS THAN ('2020-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p202004 VALUES LESS THAN ('2020-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p202005 VALUES LESS THAN ('2020-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p202006 VALUES LESS THAN ('2020-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p202007 VALUES LESS THAN ('2020-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p202008 VALUES LESS THAN ('2020-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p202009 VALUES LESS THAN ('2020-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p202010 VALUES LESS THAN ('2020-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p202011 VALUES LESS THAN ('2020-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p202012 VALUES LESS THAN ('2021-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p202101 VALUES LESS THAN ('2021-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p202102 VALUES LESS THAN ('2021-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p202103 VALUES LESS THAN ('2021-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p202104 VALUES LESS THAN ('2021-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p202105 VALUES LESS THAN ('2021-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p202106 VALUES LESS THAN ('2021-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p202107 VALUES LESS THAN ('2021-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p202108 VALUES LESS THAN ('2021-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p202109 VALUES LESS THAN ('2021-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p202110 VALUES LESS THAN ('2021-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p202111 VALUES LESS THAN ('2021-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p202112 VALUES LESS THAN ('2022-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p202201 VALUES LESS THAN ('2022-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p202202 VALUES LESS THAN ('2022-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p202203 VALUES LESS THAN ('2022-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p202204 VALUES LESS THAN ('2022-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p202205 VALUES LESS THAN ('2022-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p202206 VALUES LESS THAN ('2022-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p202207 VALUES LESS THAN ('2022-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p202208 VALUES LESS THAN ('2022-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p202209 VALUES LESS THAN ('2022-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p202210 VALUES LESS THAN ('2022-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p202211 VALUES LESS THAN ('2022-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p202212 VALUES LESS THAN ('2023-01-01 00:00:00') ENGINE = InnoDB,
PARTITION p202301 VALUES LESS THAN ('2023-02-01 00:00:00') ENGINE = InnoDB,
PARTITION p202302 VALUES LESS THAN ('2023-03-01 00:00:00') ENGINE = InnoDB,
PARTITION p202303 VALUES LESS THAN ('2023-04-01 00:00:00') ENGINE = InnoDB,
PARTITION p202304 VALUES LESS THAN ('2023-05-01 00:00:00') ENGINE = InnoDB,
PARTITION p202305 VALUES LESS THAN ('2023-06-01 00:00:00') ENGINE = InnoDB,
PARTITION p202306 VALUES LESS THAN ('2023-07-01 00:00:00') ENGINE = InnoDB,
PARTITION p202307 VALUES LESS THAN ('2023-08-01 00:00:00') ENGINE = InnoDB,
PARTITION p202308 VALUES LESS THAN ('2023-09-01 00:00:00') ENGINE = InnoDB,
PARTITION p202309 VALUES LESS THAN ('2023-10-01 00:00:00') ENGINE = InnoDB,
PARTITION p202310 VALUES LESS THAN ('2023-11-01 00:00:00') ENGINE = InnoDB,
PARTITION p202311 VALUES LESS THAN ('2023-12-01 00:00:00') ENGINE = InnoDB,
PARTITION p202312 VALUES LESS THAN ('2024-01-01 00:00:00') ENGINE = InnoDB,
PARTITION pmax VALUES LESS THAN (MAXVALUE) ENGINE = InnoDB)
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理解递归的基本原理在C语言中，递归是一种函数调用自身的编程技术。要掌握它，首先需要理解其核心思想：将一个复杂的大问题，分解为一个或几个与原问题相似但规模更小的子问题，直到子问题足够简单，可以直接求解。这个过程通常包含两个关键部分：递归出口和递归体。递归出口定义了问题何时不再继续分解，即最简单、可直接
2026-08-07
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c语言函数递归 怎么选？常见方案对比分析
递归函数的基本概念与适用场景在C语言编程中，递归是一种函数调用自身的编程技巧。它并非适用于所有问题，但在处理某些具有自相似结构的问题时，能提供极其清晰和优雅的解决方案。递归的核心思想是将一个大规模问题分解为一个或多个同类型但规模更小的子问题，直到子问题简单到可以直接求解。典型的适用场景包括树形结构的
2026-08-07
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Objective-C 内存管理入门：从 alloc 到 dealloc 的生命周期详解
理解内存管理的基石在Objective-C的编程世界中，内存管理是开发者必须掌握的核心技能之一。它直接关系到应用的性能、稳定性与资源利用效率。与一些采用自动垃圾回收机制的语言不同，Objective-C在很长一段时间里，依赖一套基于引用计数的、需要开发者部分介入的管理规则。这套规则的核心思想是明确的
2026-08-07
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如何正确使用 dealloc 以避免 iOS 应用中的内存泄漏
理解 dealloc 的角色与时机在 iOS 应用开发中，内存管理是保障应用性能与稳定性的基石。dealloc 方法是 Objective-C 中对象生命周期结束时的关键回调，它标志着对象即将被系统回收内存。正确理解其触发时机至关重要：当一个对象的引用计数降为零时，运行时系统会自动调用该对象的 de
2026-08-07
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深入理解 Objective-C 中的 dealloc 方法：内存管理核心机制
内存管理的基石在Objective-C的世界里，内存管理是开发者必须掌握的核心技能之一。作为一门在手动引用计数（MRC）时代诞生的语言，Objective-C要求程序员对对象的生命周期有清晰的认识。dealloc方法正是这一生命周期中至关重要的终点站。它是一个实例方法，当对象的引用计数降为零时，系统
2026-08-07
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理解 native2ascii：Java 国际化开发中的字符编码工具
native2ascii 工具的基本定位在Ja va应用程序的国际化与本地化开发过程中，处理非拉丁字符集是一个常见且关键的环节。Ja va内部使用Unicode字符集来统一表示全球各种语言的文字，但其属性文件（.properties）在历史上要求使用ASCII编码，或者更准确地说，要求非ASCII字
2026-08-07
0
如何使用 native2ascii 转换中文字符为 Unicode 转义序列
理解 native2ascii 工具的基本用途在软件开发，特别是涉及国际化处理的场景中，开发者常常需要处理不同编码的文本资源。native2ascii 是 Ja va 开发工具包（JDK）中提供的一个命令行实用程序，其主要功能是将包含本地字符编码（非ASCII字符）的文件，转换为包含 Unicode
2026-08-07
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Java native2ascii 命令详解：解决属性文件乱码问题
native2ascii 命令的由来与作用在Ja va开发中，处理国际化资源文件是一个常见需求。资源文件通常以.properties格式存储，用于支持多语言界面。然而，Ja va属性文件默认采用ISO-8859-1字符集编码，这导致了一个直接的问题：当文件中包含非拉丁字符（如中文、日文、韩文等）时，
2026-08-07
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一个 memwatch 实战案例：定位野指针问题
内存监控工具的价值与挑战在软件开发，尤其是使用C/C++这类手动管理内存的语言时，内存错误是程序员最常遭遇的难题之一。其中，野指针问题因其隐蔽性和破坏性，往往成为最难定位的“幽灵”缺陷。它可能潜伏在代码中，在特定条件下才被触发，导致程序崩溃、数据损坏或难以预测的行为。传统的调试手段，如打印日志或使用
2026-08-07
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极度公式是一款跨平台专业LaTeX公式识别编辑软件，支持OCR公式识别和多平台编辑。和使用说明，避免使用，享受完整功能与稳定支持。做扫描整理、文字提取和表格转换时，它能把识别后的处理步骤接得更顺，资料录入这类场景会省下不少时间。
