Tree structure is not new to everyone, but there are several trees that are really applied to the code - binary sorting tree, balanced binary tree, B tree, B + tree, red and black tree. Whether you know it or not, today, after reading this blog, you will plant it in front of your home.
Posted on Sun, 07 Jun 2020 01:31:13 -0700 by srikanthiv
###1 / General
Using Spring Boot as the basic framework, Spring Security as the security framework and WebSocket as the communication framework, point-to-point chat and group chat are realized.
###2 / dependence required
Spring Boot version 1.5.3 uses MongoDB to store data (not required). Maven relies on the following:
Posted on Mon, 25 May 2020 08:20:52 -0700 by fowlerlfc
1 create Mongodb cluster
Directly use the following yaml file to create a mongodb cluster. In this environment, only two nodes of mongodb are started. Use hostPath for data storage and create storage directory
[root@master ~]# mkdir -p /home/storage/mongo/db/
[root@master mongo]# cat mongo.yaml
name: mo ...
Posted on Fri, 08 May 2020 07:40:46 -0700 by Neoraven456
1. Use MongoDB module for operation
First, install the mongodb module in the working directory,
1 cnpm i mongodb//Lead in module
const MongoClient = require('mongodb').MongoClient;
//Write connection string,My database address is as follows,So when you're writing, just change the address
const DB_CONN_STR= 'mongodb://127.0.0.1/demo';
Posted on Sat, 02 May 2020 15:31:39 -0700 by daimoore
mongodb is liked by many programmers because it stores a lot of data, supports high concurrency and weak transactions.
For java, you need to download the java mongo driver package, similar to the mysql driver package, which contains the java operation mongo tool class.
DBCollection is used for driver package versions below 3.0...
The MongoC ...
Posted on Thu, 30 Apr 2020 01:52:10 -0700 by jdm95lude
Create mongodb sharding cluster
1, Environmental preparation
1. Server node information [three servers] x.x.x.159, x.x.x..160, x.x.x..161 2. Server system Linux x86? 64 GNU / Linux or centos7 or redhat 3. mongodb version mongodb v4.2.5 Download address: https://fastdl.mon ...
Posted on Wed, 29 Apr 2020 01:10:36 -0700 by JonathanV
1. Python Executes External Commands
1. Introduction of subprocess module
The subprocess module allows us to start a new process and connect to their input/output/error pipelines to get a return value.
This module is used to create and manage subprocesses.It provides a high-level interface to replace modules and functions such as os.system*(), ...
Posted on Tue, 28 Apr 2020 10:47:35 -0700 by ed209
Currently, Mongodb replica set is a three-node+1 arbitration node, which has been running steadily for two years. Due to the continuous update and deletion of data, a large part of the storage space has not been released. The temporary storage for viewing databases in the database is not large, and the storage is not recycled (1.8 ...
Posted on Thu, 23 Apr 2020 10:20:52 -0700 by ruttiger
Purpose: it's not a professional one. Take it and play. If it's really put into production, please move to the official website
Reference: Official website Doc The document is very rich, only look for the simplest
Mapping question: "put the elephant in the refrigerator. How many steps are there?"
The first step is to open the refri ...
Posted on Tue, 07 Apr 2020 10:29:13 -0700 by sdyates2001
In this chapter, we will continue to discuss the condition operator $type in MongoDB.
The $type operator is based on the BSON type to retrieve the matching data types in the collection and return the results.
The types that can be used in MongoDB are as follows:
Posted on Sun, 05 Apr 2020 14:31:39 -0700 by sloshire1