July 2023
Intermediate to advanced
278 pages
5h 40m
Chinese
Content preview from Trino 权威指南：原书第2版
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52
|
第
4
章
4.3 catalog
、
schema
和表
Trino
集群使用前文所述的基于连接器的架构处理所有查询。每个
catalog
都会配置一
个连接器来访问特定的数据源。数据源在
catalog
中暴露出一个或多个
schema
。每个
schema
包含表，表提供数据行，每个数据行由一些具有不同数据类型的列组成。可以在
8.3
节、
8.4
节和
8.6
节分别了解
catalog
、
schema
和表的更多信息。
4.4
查询执行模型
你已经了解，在实际使用中，
Trino
集群通常部署为一个协调器和多个工作节点。接下
来将探讨
Trino
如何实际处理
SQL
查询语句。
有关
Trino
的
SQL
支持的更多细节，请参见第
8
章和第
9
章。
理解执行模型是在
Trino
中进行查询性能调优必备的基础知识。
回忆前面的描述：终端用户通过
CLI
，使用
ODBC
或
JDBC
客户端，或使用其他客户端
库来发送
SQL
语句到协调器。协调器之后调用工作节点从数据源获得数据、创建结果数
据集并将结果返回给客户端。
我们先仔细了解一下协调器内部的情况。首先，
SQL
语句以文本形式提交到协调器，协
调器解析和分析
SQL
语句。之后，
Trino
创建一个由内部数据结构表示的执行计划，叫
作查询计划。图
4-6
展示了这一流程。查询计划全面地表示了对每条
SQL
语句处理数据
和返回结果所需进行的步骤。
计划器 / 优化器解析器 / 分析器
图 4-6：处理一条 SQL 查询语句并创建查询计划
如图
4-7
所示，查询计划生成过程使用元数据
SPI
和数据统计
SPI
来创建查询计划。也
就是说，协调器会使用 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.