Tag: dex

In mysql, does != use the index?

In mysql !=, should I use the index? Many people wonder whether != should be indexed. It can be definitely said that this operation can be indexed, but in actual situations, why is it not indexed? First of all, we need to know that indexing has a great relationship with the amount of data and […]

Mysql series-index type

1. Index type type Index type classified according to the content of leaf nodes InnoDB uses the B + tree index model. It is divided into primary key index and non-primary key index according to whether the leaf node stores data (according to the content of the leaf node); non-primary key index includes: ordinary index, […]

MySQL index module

1. Why does MySQL database use B + tree to store indexes? If you only select one piece of data, hashing is indeed faster. However, multiple items are often selected in the database. At this time, because the B + tree index is ordered and connected by a linked list, its query efficiency is much […]

Typescript generics, keyof, typeof, index type, mapping

Typescript generics A major part of software engineering is building components that not only have well-defined and consistent APIs, but are also reusable. Components that can handle today’s and tomorrow’s data will give you the most flexible ability to build large software systems. Use generic type variables function identity<Type>(arg: Type): Type { return arg; } […]

7000 words | In-depth explanation of MySQL index

Hello, I am Wukong. The directory of this article is as follows: 1. Foreword Recently, I have been sorting out the core knowledge of MySQL, and I just happened to sort out the knowledge related to MySQL indexes. Many of my articles are based on principles + practical methods to help you understand the knowledge […]

ElasticSearch index operations

This article uses DSL to operate ES and SpringBoot to operate ES. More ElasticSearch entry-to-practice tutorials: Click to view 2.1 Index operation ES index is a container for storing data, similar to a database. 2.1.1 Create index 1. DSL syntax PUT indexname {<!– –> “settings”: {<!– –> “number_of_shards”: 1, “number_of_replicas”: 1 }, “mappings”: {<!– –> […]

Using Junit to unit test the BMI index

This test is a practical use of the Junit test platform. Junit is a unit testing framework for Java language. It was founded by Kent Beck and Erich Gamma and has gradually become the most successful one in the xUnit family derived from Kent Beck’s sUnit. Junit has its own extended ecosystem. Most Java development […]

Batch operation of elasticsearch index

Batch operations for indexes Batch query and batch addition, deletion and modification Batch query GET /_mget Batch write: POST /_bulk POST /<index>/_bulk {“action”: {“metadata”}} {“data”} Notice: The bulk api has strict requirements on json syntax. Except for delete, each operation requires two json strings (metadata and business data), and each json string cannot have a […]

[MySQL Indexing and Optimization] Database design practice (including ER model)

Database design practice (including ER model) Article directory Database design practice (including ER model) 1. ER model 1.1 Overview 1.2 Modeling analysis 1.3 Refinement of ER model 1.4 Convert ER model diagram into data table 1. Convert an entity into a database table 2. Convert a many-to-many relationship into a data table 3. Express a […]