Index definition, classification and use

... 索引 1, what is an index? What are the common types of indexes? Index is a way to speed up the retrieval of data in a table. The index of the database is similar to the index of a book. In books, the index allows users to quickly find the information they need without having to flip...


MySQL performance optimization

... MySQL performance indicators refer to response time. Analysis of performance includes profiling of the application and profiling of MySQL queries. Profile application A better performance optimization tool for the application, New Relic, has installation steps in the collection. The...


The Redis database common command

... Redis is an open source, log-based, Key-Value database that can be written in ANSI C, supports the network, and can be persisted based on memory, and provides APIs in multiple languages. Redis is a high performance key-value database. The emergence of Redis greatly compensates for the...


The difference between inserting data value and values ​​in mysql

... value and values ​​difference VALUE insert multiple rows VALUES insert multiple rows contrast, when inserting multiple rows, use VALUE faster According to the conclusions, you should use VALUES when inserting a single line and VALUE when inserting multiple lines. Tucao: I have to say...


Setting up replication (master-slave replication) a master multi-book

... mysql database installation reference again is not detailed, this article uses mysql8.0.12 introduction master-slave replication involves a single master server and more From the server, the structure is as follows, all master-slave replication is based on binary log Open master-slave...


MySQL key_len size calculation

... background: When using Explain to view the SQL execution plan, there are columns showing the value of key_len. According to this value, the length of the index can be judged. I learned which part of the field used to index. 环境: CREATE TABLE `tmp_0612` ( `id` int(11) NOT NULL, `name`...


Common usage of pandas module

... 一, import module import time,random import pandas as pd import numpy as np 二, usage 说明: df object is df=pd.DataFrame(dict) The s object is s=pd.Series(data=dict) 1, import data pd.read_csv(filename): import data from CSV file Pd.read_table(filename): Import data from a text file that...


Mybatis's level 1 cache and level 2 cache

... Mybatis's level 1 cache and level 2 cache are included with Mybatic. Purpose: Store the query result of sql in the cache. When querying again, it will be taken directly from the cache instead of being obtained from the database. This will speed up the query, but will result in dirty...


Spring boot (3): The use of Redis in Spring boot

... Spring boot In addition to the commonly used database support, the nosql database is also packaged and automated. 1 Redis Introduction Redis is the most widely used memory data storage in the industry. Compared to memcached, (1) Redis supports richer data structures such as hashes,...


Scrapy_redis deploys distributed crawlers

... NO.1 First enter your own python environment by using the command: pip install scrapy_redis to install the required kit. NO.2 Configured in the settings of the crawler project #Configure the scheduler used by scrapy #Configuring scrapy practical de-classification #Configuring storage...