mongodb

问题 Although there are many proper tutorials to show how to connect relational database in Java, I really in doubt with the MongoDB mechanism working with Java. Normally people would create a connection in context.xml to interact with a relational database with JSP/servlet to do web project. However, with NoSQL database, I don't quite get any resources on how to perform this connection in a nice constructed way rather than many resources with framework lately and working seamlessly. If any

问题 How do I go about writing an $addFields query in Spring Data MongoDB Reactive for a simpler and a slightly more complex field addition as shown below: db.getCollection("mycollection").aggregate( [ { "$addFields" : { "existingObjectField.newFieldArray" : [ "$existingObjectField.existingFieldObject" ] } }, { "$addFields" : { "existingFieldArray" : { "$map" : { "input" : "$existingFieldArray", "as" : "item", "in" : { "existingFieldObject" : { "_id" : "$$item. existingFieldObject._id",

问题 Although there are many proper tutorials to show how to connect relational database in Java, I really in doubt with the MongoDB mechanism working with Java. Normally people would create a connection in context.xml to interact with a relational database with JSP/servlet to do web project. However, with NoSQL database, I don't quite get any resources on how to perform this connection in a nice constructed way rather than many resources with framework lately and working seamlessly. If any

问题 I have an Android that uses firebase for authentication and MongoDb as a backend, I'm currently on the M0 cluster where the connection limit is 500. I use the Stitch API. When I use app from my device the number of connections increases from 4 to 8. I think initial 4 connections are by default so I don't mind that but I'm really concerned about such a jump in number of connections from a single device. PS. I tried having StitchAppClient and RemoteMongoClient in common class, so that there

问题 I need to extract the first item from an array and add it to its own object, so I found $first the does exactly that https://docs.mongodb.com/manual/reference/operator/aggregation/first-array-element/#example However, I was getting the error Unrecognized expression '$first' and thought it was my query that wasn't working, so I cloned the exact example they have in their docs, but it gives me the same error. db.runninglog.insertMany([ { "_id" : 1, "team" : "Anteater", log: [ { run: 1, distance

问题 How do I go about writing an $addFields query in Spring Data MongoDB Reactive for a simpler and a slightly more complex field addition as shown below: db.getCollection("mycollection").aggregate( [ { "$addFields" : { "existingObjectField.newFieldArray" : [ "$existingObjectField.existingFieldObject" ] } }, { "$addFields" : { "existingFieldArray" : { "$map" : { "input" : "$existingFieldArray", "as" : "item", "in" : { "existingFieldObject" : { "_id" : "$$item. existingFieldObject._id",

问题 I have a studentSchema in which there are pass property with default value 0(means that time student does not having any concession pass). When student make a request for the pass , if the admin accept that request then student will gets his pass and the value of pass property gets updated to 1(means now student has the pass ) . And also this pass only available for some days e.g.one or two months . after one month has been completed student needs to request for the new pass. **codeshareio

问题 I want to find the subdocument in mongoose by subdocument id. i am doing : mainDoc.subDocFieldName.id(sudocId); But it shows 'cannot find property id of undefined' seems like mainDoc.subDocFieldName is undefined . so how do i access the sub document.? 回答1: I solved this problem by : mainDoc[subDocFieldName].id(sudocId); Actually I was using subDocument array. 来源： https://stackoverflow.com/questions/18586391/how-to-find-the-subdocument-via-subdocument-id-in-mongoose

问题 I am trying to create a function that InsertOne data by wrap transaction, and I already to replica set in mongodb also, I tried in local and and MongoDB atlas the error were same, here is the code: const MONGODB_URI = "mongodb://localhost:27017,localhost:27018,localhost:27019/?replicaSet=rs" ctx := context.Background() client, err := mongo.Connect(ctx, options.Client().ApplyURI(MONGODB_URI)) if err != nil { panic(err) } db := client.Database("production") defer db.Client().Disconnect(ctx) col

问题 after seting my connections const mongoose = require('mongoose') const Post = require('./database/models/Post') mongoose.connect("mongodb://localhost/testdb", {useNewUrlParser: "true", useUnifiedTopology: true}) and my server page as below: const mongoose = require('mongoose') const app = new express() //mongoose.connect('mongodb://localhost/node-js-blog') //mongoose.connect("mongodb://localhost:27017/node-js-blog", {useNewUrlParser: "true",}) mongoose.connect('mongodb://localhost/node-js