基于eui的白鹭引擎H5小游戏入门总结

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Coinciding with the new native data dictionary in MySQL 8.0, we have made a number of useful enhancements to our INFORMATION_SCHEMA subsystem design in MySQL 8.0. In this post I will first go through our legacy implementation as it has stood since MySQL 5.1, and then cover what’s changed.

与MySQL 8.0原生数据字典一致，在MySQL 8.0的INFORMATION_SCHEMA子系统设计中，我们做了一些很有用的增强。在这篇文章中，我将会介绍自MySQL 5.1以来的旧的实现方式，然后介绍我们做了什么改变。

Background

INFORMATION_SCHEMA was first introduced into MySQL 5.0, as a standards compliant way of retrieving meta data from a running MySQL server. When we look at the history of INFORMATION_SCHEMA there have been a number of complaints about the performance of certain queries, particularly in the case that there are many database objects (schemas, tables etc).

INFORMATION_SCHEMA首次引入MySQL 5.0，作为一种从正在运行的MySQL服务器检索元数据的标准兼容方式。当我们回顾INFORMATION_SCHEMA的历史时，对于某些特定查询性能总是有很多的抱怨，特别是在有许多数据库对象（schema，表等）的情况下。eui64.tw

In an effort to address these reported issues, since MySQL 5.1 we have made a number of performance optimizations to speed up the execution of INFORMATION_SCHEMA queries. The optimizations are described in the MySQL manual, and apply when the user provides an explicit schema name or table name in the query.

为了解决这些上报的问题，从MySQL 5.1开始，我们进行了许多性能优化来加快INFORMATION_SCHEMA查询的执行速度。MySQL手册<链接1>中描述了这些优化，当用户在查询中提供显式schema名称或表名时，将会应用这些。eui64.tw

Alas, despite these improvements INFORMATION_SCHEMA performance is still a major pain point for many of our users. The key reason behind these performance issues in the current INFORMATION_SCHEMA implementation is that INFORMATION_SCHEMA tables are implemented as temporary tables that are created on-the-fly during query execution. These temporary tables are populated via:

 

1. Meta data from files, e.g. table definitions from .FRM files.

2. Details from storage engines, e.g. dynamic table statistics.

3. Data from global data structures in the MySQL server.

 

尽管有这些改进，INFORMATION_SCHEMA的性能仍然是我们许多用户的主要痛点。在当前INFORMATION_SCHEMA实现方式下产生的性能问题背后的关键原因是，INFORMATION_SCHEMA表的查询实现方式是在查询执行期间创建临时表。这些临时表通过以下方式填充：