Tag:Full table

  • MySQL_ Index optimization


    MySQL index optimization The following notes are from this video:https://www.bilibili.com/video/BV1KW411u7vy?p=20&share_source=copy_web Note the index order when combining indexes image.png Index optimization In the union index (a, B, c), using filesort will be generated in the following cases where a=1 and b>2 order by c After a = 1 is queried, b > 2 is queried, but […]

  • [20211108] index split block clear log increase (unique index) 2 txt


    [20211108] index split block clear log increase (unique index) 2 txt –//Link http://blog.itpub.net/267265/viewspace-2840853/ Tested the strange phenomenon encountered in index splitting.–//Look at what happens when the unique index splits. The maximum value was inserted during the test of the unique index last week. There is a 10-90 split. It is not well designed. You should […]

  • Handler_ read_* Summary of


    When analyzing the performance of an SQL, in addition to the execution plan, another commonly seen indicator is the “handler_read_ *” related variable. Handler_read_key Handler_read_first Handler_read_last Handler_read_next Handler_read_prev Handler_read_rnd Handler_read_rnd_next These seven variables are also explained in the official documents, but many people are still confused after reading them. Let’s take a look at the […]

  • [fault announcement] one stored procedure brings down the whole database


    I’m very sorry. During 15:00-16:00 this afternoon, one stored procedure for querying the number of classified blog posts of the website cached the execution plan with extremely poor performance, resulting in full table scanning and the collapse of the whole database server, resulting in slow or 500 website access. This has brought you great trouble, […]

  • SQL index optimization


    [development] SQL optimization ideas (taking Oracle as an example) powered by wanglifeng https://www.cnblogs.com/wanglifeng717 Optimization of single table query Single table query is the simplest and most important module. It is the basis of multi table query. Avoid repeated scanning of data If you can scan the data at one time, don’t scan it again. If […]

  • Database mysql considerations and SQL optimization


    Be careful1、delete、truncate、drop; It can be understood that for a book, delete is to tear up the directory, truncate is to tear down the contents of the book and burn it, and drop is to burn the book2. Use insert into select with caution. The select statement will lock the relevant data. If there is no […]

  • My colleague was fired after using insert into select in the company


    For the lesson of blood, please use insert into select with caution. After the application by colleagues, the company lost nearly 10W yuan and was finally dismissed by the company. The cause of the matter The transaction volume of the company is relatively large. The database used is mysql, and the daily increment is about […]

  • 4) MySQL index optimization


    Index optimization 1. Try to match all values When the index is created, the index column can be used in the where condition as much as possible.For example, alter table staffs add index idx_ staffs_ nameAgePos(name,age,pos);Try to add three columns in where, explain select * from stacks where name = ‘July’ and age = 25 […]

  • Getting to know the index in mongodb


    The index is like a book directory, which allows us to quickly locate the required content. There are indexes in relational databases and NoSQL. In this article, we will briefly introduce the indexes in mongodb. This is the ninth article in mongodb series. Understanding the previous articles will help you better understand this article: 1.Installing […]

  • 5 minutes to quickly master the core technology of Alibaba’s internal MySQL performance optimization!


    preface The interview of batjtmd and other large factories is becoming more and more difficult, but no matter from large factories or small companies, one of the unchanged key points is the investigation of SQL optimization experience. When it comes to database, first “tell me your opinion on SQL optimization?”. SQL optimization has become a […]

  • Meaning of Mongo slow log field


    View the slow log configuration of the current clusterdb.getProfilingStatus(); // If slowms: indicates the time of slow log configurationdb.getProfilingLevel(); // Indicates whether to write the slow log to the system table db.system.profile. 0 means off, 1 means on. Lock mode of MongoMode DescriptionR representatives shared (s) lock. / / sharedW representatives exclusive (x) lock. / […]

  • No, no? MySQL indexing best practices don’t you look at


    The author is talkative The busy week has passed again. The biggest fun of this week is to buy a small speaker and start practicing the piano happily after work. Programmers still have to cultivate some artistic bacteria. ha-ha I didn’t plan to write anything this week. On Friday, the company held an internal technology […]