Discussion on the correct usage of JSON: Pyhong, MongoDB, JavaScript and Ajax
About this article This article mainly summarizes some of the problems encountered in transmitting JSON data since the website was written and the current solutions. The website database uses MongoDB, the back-end is Python, and the front-end uses Riot.js in a “semi-separated” form. The so-called semi-separation means that the first page data is directly rendered into HTML through the server-side template engine, thus avoiding the need to load the home page twice. problem, while other dynamic content is loaded using Ajax. The data in the entire process is transmitted in JSON format, but different methods need to be used in different links and some different problems are encountered. This article mainly records and summarizes. 1. What is JSON? JSON (Javascript Object Notation) is a lightweight data exchange language conceived and designed by Douglas Crockford. Its predecessor XML may be known earlier. Of course, JSON does not exist to replace XML, but it is smaller than XML and more suitable for data transfer in web development (JSON is to Javascript like XML is to Lisp). As can be seen from the name, the format of JSON conforms to the syntax format of “object” in the Javascript language. In addition to Javascript,…
How to make it best for query search, Mongodb?
json mongodb python Server Write your review! Come on, watch it all Member login | User registration Recommended reading python Python Python Python 100 practice projects 1. Taobao simulated login 2. Tmall product data crawler 3. Crawl the data of the products I have purchased on Taobao 4. Send messages through WeChat to remind my girlfriend at different times every day 5. Crawl 5K resolution ultra-clear and beautiful wallpapers 6. Crawl Douban ranking movie data (including GUI interface version)… [detailed] Crayon Shin-chan 2023-10-16 18:29:34 go ppurl Allegro summary: 1. SolderMask: also known as green oil layer, PCB non-wiring layer, used to make screen printing boards, apply solder mask to areas that do not need to be soldered. Reserved on the solder mask The size of the pad is larger than the actual pad, and the difference is generally… [detailed] Crayon Shin-chan 2023-10-17 18:30:39
Find object in nested array, mongodb, compass
I am using Mongodb database and Compass tool to visualize my data. My collection “ProbCancer” looks like this: probCancers: [ cases: [ { case: { bi: Number, age: Number, }, level: Number, _id: false, } ] ] Since there are many objects in the cases array, it is difficult to analyze it. I only want to find objects with level = -1. Is there any way to perform this query in compass? Entering the query parameter db.probCancers.find(query); might also help me. 1> Ash..: Unfortunately, Compass does not support $elemMatch projection. There is an open tracker for this issue. (I don’t have enough reputation to comment on Bentaiba’s answer.)
mongodb, $sum field on array of objects
I’m new to mongodb, maybe I’m missing something. But there are many samples on the internet and it’s still difficult to get the total number on one field of an object array. This is what I’m doing: db.collection.insertMany([ { id: “6002010011500”, balance: [ { type: “PR”, amount: “1000” }, { type: “IN”, amount: “300” } ] }, { id: “5001010001005”, balance: [ { type: “PR”, amount: “-3000” }, { type: “IN”, amount: “-600” } ] } ]) Try different ways to get the total amount: db.collection.aggregate([ { $group: { _id: null, TotalBalance: { $sum: “$balance.amount” } } } ]) Get balance 0 instead of -2300 { “_id” : null, “TotalBalance” : 0 } Same thing as $ unwind: db.collection.aggregate([ { $unwind: “$balance” }, { $group: { _id: null, TotalBalance: { $sum: “$balance.amount” } } } ]) What did I do wrong? Thanks 1> mickl..: You store amount as a string, but if you want operator, it should be Number$sum. Try db.collection.insertMany([ { id: “6002010011500”, balance: [ { type: “PR”, amount: 1000 }, { type: “IN”, amount: 300 } ] }, { id: “5001010001005”, balance: [ { type: “PR”, amount: -3000 }, { type: “IN”, amount: -600 } ] } ])…
Mongodb, conditional $sum
File: [ { name: ‘abc’ length: 25, area: 10 }, { name: ‘abc’, length: 5 } ] Output after summary query: [ { count: 2, summarizedLength: 30, summarizedArea: null, _id: { name: ‘abc’ } } ] The length and area should be summarized. But only if all documents have the area or length attribute. Therefore, if an attribute grouped by length is missing any attribute, then the summarizedLength value should be null/undefined/not exisitng and equal to Same as area. I tried this: let query = mongoose.model(‘mycollection’).aggregate([ { $group: { _id: { name: $name }, count: { $sum: 1 }, summarizedLength: { $sum: “$length” }, summarizedArea: { $sum: “$area” }, } } ]); The problem is, I need to cancel $sum if any attributes are missing. is it possible? 1> Saravana..: From the Mongo documentation $sum behavior If used on a field containing both numeric and non-numeric values, $sum ignores the non-numeric values and returns the numeric sum. If used for a field that does not exist in any document in the collection, $sum returns 0 for the field. $sum returns 0 if all operands are non-numeric. We can $push arrange all the areas and lengths into an array, and count…
2018.10.17HDFS, Hive, HBase, MongoDB, Redis, ES
HDFS: Hadoop’s distributed file system is called HDFS, which is a file system designed for storing very large files in a streaming data access mode. HDFS is suitable for: Storing and managing petabytes of data Processing unstructured data Focus on data processing throughput The application mode is: write once and read many times Not suitable for: Storing small files A large amount of randomness Need to modify files Hive: Hive is a data warehouse tool built on top of Hadoop. It can query and manage PB-level distributed data. It is suitable for For batch processing of large-scale data, Hive itself does not store data. It relies on HDFS and Mapreduce and provides a simple SQL-like query language HiveQL. However, there are some restrictions on using hive, and some standard sql does not exist in hive. The query speed is slow and does not provide real-time query and row-level data update operations. HBase: HBase is a distributed, column-oriented open source non-relational database (NoSQL) based on HDFS The file system supports efficient reading and writing at the record level, which is not suitable for offline analysis scenarios. Suitable for light query application scenarios with simple structure but very large data volume (usually…
mongodbphp,mongodb
php tutorial|php manual mongodb php tutorial – php manual mongodb php, mongodb Simple mobile mall app source code download, kernel compilation and installation of ubuntu, qq friend information crawler, keywords for creating objects in the php program, seo nail art lzw First install the extension, and then you can use mongodb beautiful real estate source code, ubuntu native wallpaper download, anti-crawler school recruitment, popen php, Yangchun foreign trade seolzwA, connect to the databasedelphi excel source code download, ubuntu system copy, tomcat The browser is opened, the crawler software is punished, PHP declares an empty object, Huaian City, Jiangsu Province Network seolzw try { $mOngo= new MongoClient(); $db = $mongo->mydb; var_dump($db);} catch (MongoConnectionException $e) { echo $e->getMessage();} This code can connect to the mydb database. If the database does not exist, it will be automatically created. B. Create a collection try { $mOngo= new MongoClient(); $db = $mongo->mydb; $mycol = $db- >createCollection(‘mycol’); var_dump($mycol);} catch (MongoConnectionException $e) { echo $e->getMessage();} This code can create the collection mycol. C. Insert documents Insert() is used in mongodb to insert documents. try { $mOngo= new MongoClient(); $db = $mongo->mydb; $mycol = $db->mycol; $document = array(‘name’ => ‘test1’ , ‘ sex’ => ‘formale’ , ‘age’ =>…
Synchronize data across multiple occasionally connected clients using EventSourcing (NodeJS, MongoDB, JSON)
I’m having trouble implementing data synchronization between a server and multiple clients. I read about event sourcing and I want to use that to do the synchronization part. I know this is not a technical issue, but a conceptual issue. I’m just sending all events to the server, but the client is designed to be used offline from time to time. This is the basic concept: The server store each client should know that it will not replay these events to serve the data, since the main purpose is to synchronize events between clients so that they can be stored locally Replay all events for all events. The client has a JSON store in it that also makes all the events and reconstructs all the different collections from the stored/synchronized events. Since clients can modify data offline, it is not important to have consistent synchronization cycles. With this in mind, the server should handle conflicts when merging different events and ask specific users when conflicts occur. So the main problem for me is to determine the difference between client and server to avoid sending all events to the server. I also have a problem with the order of the synchronization…
Mongodb, consisting of appointments and hours
I’m actually developing an application and I need to get some information from my database: I have a trait model and I have a user, The trait model has a start date and an end date, both of which are in date format, so mongodb can use ISODate() What I need is to get the date difference for all “traitements” by the user, but in hourly format. For example, if the harassment started on 24/02/2015 08:00:00 and ended on 24/02/2015 at 10:00 Ends at 00:00, I need “2” hours. This is my actual situation: @TraitementNettoyage.aggregate([ {$group: {‘_id’: {user: ‘$user’}, time: {‘$subtract’: [‘$dateSortie’, ‘$dateEntre’]}}}, {$sort: {_id: 1}} ]).exec((err, res)=> console.log res ) This request does not work and tells me $subtract is an unknown group operator. Edit: I can use $subtraction but I don’t know how to group. Can you help me? This is my new code without groups: Traitement.aggregate([ {$project: {total: {$subtract: [‘$dateSortie’, ‘$dateEntre’]}}}, {$sort: {_id: 1}} ]).exec((err, res)=> console.log res ) The last part is to group them by user properties, I don’t know how to make it work: – / Edit 2: Documents I need: [{ “_id”: { “user”: { “_id”: “5512a66db54f879c2887411f”, “userLastname”: “Toto”, “userFirstname”: “Toto” }, “total”:…
Performance test: Things to pay attention to when comparing self-built databases with RDS (applicable to MySQL, SQLSERVER, MongoDB)
Performance testing: Things to note when comparing self-built databases with RDS Background Many users often compare and test the performance differences between self-built databases and RDS, and their test results Often RDS is not as good as ECS self-built. From the perspective of database testing, the test must first be conducted fairly before the results can be convincing. As a public relational database service, RDS must include stability, high availability, high security, and then high performance. Without the first two, I believe not many people would be willing to use services that are both unstable and unsafe. Therefore, in terms of stability, RDS must have active and backup dual nodes. The dual nodes are even in different computer rooms. If one of the computer rooms is abnormal, it can be quickly switched to another computer room. Secondly, RDS must ensure data security. If a piece of data you wrote and submitted suddenly disappears, and if one day your database is suddenly SQL injected by a hacker, will you still be willing to continue using RDS? As a service provider, RDS must consider data security for users. In terms of data access, RDS has added a middle layer. After all requests…
