2009 年 12月随笔档案 - Keep Walking

clustered index disadvantages in mysql

摘要：If you don’t define a primary key, InnoDB will try to use a unique nonnullable indexinstead. If there’s no such index, InnoDB will define a hidden primary key for youand then cluster on th... 阅读全文

posted @ 2009-12-10 14:20 Keep Walking 阅读(2126) 评论(0) 推荐(0) 编辑

mysql混合存储类型对事务影响

摘要：Mixing storage engines in transactionsMySQL doesn’t manage transactions at the server level. Instead, the underlying storageengines implement transactions themselves. This means you can’t ... 阅读全文

posted @ 2009-12-09 11:07 Keep Walking 阅读(1915) 评论(0) 推荐(0) 编辑

Bit-Packed Data Types

摘要：MySQL has a few storage types that use individual bits within a value to store datacompactly. All of these types are technically string types, regardless of the underlyingstorage format and manipulati... 阅读全文

posted @ 2009-12-08 16:31 Keep Walking 阅读(1993) 评论(0) 推荐(0) 编辑

VARCHAR and CHAR differences in mysql

摘要：String TypesMySQL supports quite a few string data types, with many variations on each. Thesedata types changed greatly in versions 4.1 and 5.0, which makes them even morecomplicated. Since MySQL 4.1,... 阅读全文

posted @ 2009-12-08 15:30 Keep Walking 阅读(1702) 评论(0) 推荐(0) 编辑

Avoid NULL if possible in mysql

摘要：You should define fields as NOT NULL whenever you can. A lot of tables includenullable columns even when the application does not need to store NULL (theabsence of a value), merely because it’s ... 阅读全文

posted @ 2009-12-08 14:57 Keep Walking 阅读(1749) 评论(0) 推荐(0) 编辑

Why Benchmark?

摘要：Many medium to large MySQL deployments have staff dedicated to benchmarking.However, every developer and DBA should be familiar with basic benchmarkingprinciples and practices, because they’re b... 阅读全文

posted @ 2009-12-05 18:25 Keep Walking 阅读(347) 评论(0) 推荐(0) 编辑

The InnoDB Engine

摘要：The InnoDB Engine InnoDB was designed for transaction processing—specifically, processing of many short-lived transactions that usually complete rather than being rolled back. It remains the ... 阅读全文

posted @ 2009-12-05 14:08 Keep Walking 阅读(764) 评论(0) 推荐(0) 编辑

MYSQL MVCC实现及其机制

摘要：多版本并发控制　　Multiversion Concurrency Control　　大部分的MySQL的存储引擎，比如InnoDB，Falcon，以及PBXT并不是简简单单的使用行锁机制。它们都使用了行锁结合一种提高并发的技术，被称为MVCC（多版本并发控制）。MVCC并不单单应用在MySQL中，其他的数据库如Oracle,PostgreSQL,以及其他数据库也使用这个技术。　　MVCC避免... 阅读全文

posted @ 2009-12-05 13:08 Keep Walking 阅读(7352) 评论(1) 推荐(2) 编辑

构建高性能web网站

摘要：这本书从拿到手里到看完最后一页，十天时间，每天都能从书里得到很多启发，自己也给网站的未来的框架有了一个比较清晰的发展思路，而且已经在网站上应用了其中的一些技术和观点。也养成了自己每天7点半坐公交车不坐城铁，每天只在公交车上看书的习惯，在接下来的日子里，将开始着重精读《high performance mysql 2》这本书，据说是最有深度的mysql书籍了。也期望这本书能指导我现在的mysql更... 阅读全文

posted @ 2009-12-05 07:59 Keep Walking 阅读(328) 评论(0) 推荐(0) 编辑

使用context_info传递上下文信息禁用会话级触发器

摘要：如何在会话级别禁用触发器是个问题，因为sql server并没有提供一个管理手段可以在会话级禁用触发器，它只提供alter table 表名 disable trigger 触发器名类似这种，而这种方法一旦执行，那如果在同一时间的其他过程，也不会执行触发器。但是我们可以巧妙绕道使用 context_info 来让触发器支持会话级别的禁用。新建触发器[代码]如果要在会话级禁用触发器，只需... 阅读全文

posted @ 2009-12-02 14:27 Keep Walking 阅读(1795) 评论(1) 推荐(1) 编辑

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