March 2021
Intermediate to advanced
265 pages
6h 50m
Chinese
Content preview from Presto实战
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Presto
的架构
｜
41
4.2
协调器
Presto
协调器
负责接收用户
SQL
查询
、解析查询语句、规划查询执行并管理工作节点。
协调器是
Presto
集群的大脑
，所有客户端应用程序都会连接它。用户可以通过
Presto CLI
、
使用
JDBC
或
ODBC
驱动的应用程序以及其他语言下可用的客户端库来与协调器交互
。协
调器接收客户端发送来的
SQL
语句（如
SELECT
查询）并执行。
一个
Presto
集群至少包含一个协调器
，可能包含一个或多个工作节点。在开发和测试场景
下，单个
Presto
实例可以同时承担协调器和工作节点的职责。
协调器会跟踪每个工作节点的动态，并协调查询任务的执行。对于一条查询，协调器将创
建一个包含多个
Stage
（阶段）的逻辑模型。
图
4-3
展示了客户端、协调器和工作节点之间的通信。
协调器
工作节点
工作节点
工作节点
图 4-3：处理 SQL 语句时客户端、协调器和工作节点之间的通信
一旦接收到一条
SQL
语句，协调器就负责解析、分析、优化和调度查询任务在
Presto
工
作节点上的执行。查询语句被翻译成一系列相连的任务（
T
ask
），这些任务被分发到各个
工作节点上执行。在工作节点处理数据的同时，协调器会将结果抽取出来放到输出缓冲区
中，并将缓冲区的内容暴露给客户端。一旦客户端读完输出缓冲区的内容，协调器就会代
表客户端向工作节点请求更多的数据。另外，工作节点也在不断地与数据源交互并从中读
取数据。最终，客户端不断地请求数据，工作节点则不断地从数据源读取数据并提供给客
户端，直到查询执行结束。
协调器、工作节点和客户端基于 ...
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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.