PostgreSQL EXPLAIN glossary

栏目: IT技术 · 发布时间: 4年前

内容简介:This tells us that Postgres would do aWe have documented many of the operations and field definitions you’re likely to come across while using EXPLAIN, along with performance advice and links to further learning resources.For advice in the context of your

EXPLAIN is the command used to request the execution plan for a query. It is incredibly useful when you want to explore what is going on, and see if there could be a more efficient way.

PostgreSQL does an amazing job populating query plans with useful information, but reading and understanding them can be tricky.

Here is a simple example:

Query
----------
explain select * from t order by c;

Query plan
----------
 Sort  (cost=813.32..837.48 rows=9664 width=32)
   Sort Key: c
   ->  Seq Scan on t  (cost=0.00..173.64 rows=9664 width=32)

This tells us that Postgres would do a sequential scan of our table “t”, then a sort by column “c”. The numbers tell us the startup cost , the total cost , the plan rows , and the plan width at each stage.

We have documented many of the operations and field definitions you’re likely to come across while using EXPLAIN, along with performance advice and links to further learning resources.

For advice in the context of your query plans, check out our product pgMustard .

Last updated: June 2020, PostgreSQL 12

Issue reports and suggestions are welcome, please get in touch .


以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持 码农网

查看所有标签

猜你喜欢:

本站部分资源来源于网络,本站转载出于传递更多信息之目的,版权归原作者或者来源机构所有,如转载稿涉及版权问题,请联系我们

创业就是要细分垄断

创业就是要细分垄断

李开复、汪华、傅盛 / 文化发展出版社 / 2017-5-1 / CNY 45.00

对各方面资源极为有限的创业公司而言,想在激烈的市场竞争中站立下来的第一步是:成为细分市场的垄断者。不管是资本还是尖端人才,追逐的永远是行业里尖端的企业,第二名毫无意义。 首先,要精准定位潜在市场。这个市场的需求仍没有被满足,并且潜力巨大。其次,抓住时代和行业的红利,通过高速增长实现“小垄断”,抢滩登陆。最后,在细分领域里建立起自己的竞争壁垒,应对巨头和竞争对手的复制,去扩展更大的市场,从而扩......一起来看看 《创业就是要细分垄断》 这本书的介绍吧!

Base64 编码/解码
Base64 编码/解码

Base64 编码/解码

Markdown 在线编辑器
Markdown 在线编辑器

Markdown 在线编辑器

HSV CMYK 转换工具
HSV CMYK 转换工具

HSV CMYK互换工具