mongodb-query

问题 EDIT: My original question was MongoDb Aggregation: Can you $unwind an input document variable in the pipline of a $lookup stage? Consider the code below: {$lookup: { from:"mydoc", let: {"c":"$myArray"}, pipeline: [ {$unwind: "$$c"}, ] as:"myNewDoc" }} How would I unwind c if I wanted to? /////END OF ORIGINAL QUESTION -----EDIT----- From Tom Slabbaert's comment we now know that it is possible to $unwind an input document variable in the pipline of a $lookup stage. But it is not recommended.

问题 EDIT: My original question was MongoDb Aggregation: Can you $unwind an input document variable in the pipline of a $lookup stage? Consider the code below: {$lookup: { from:"mydoc", let: {"c":"$myArray"}, pipeline: [ {$unwind: "$$c"}, ] as:"myNewDoc" }} How would I unwind c if I wanted to? /////END OF ORIGINAL QUESTION -----EDIT----- From Tom Slabbaert's comment we now know that it is possible to $unwind an input document variable in the pipline of a $lookup stage. But it is not recommended.

问题 Why do I have to use this code: { $match: { $expr: { <aggregation expression> } } } to match a document using a document input variable as opposed to doing: { $match: { <query> } } ? For example: $lookup: { from: "comments", let: { myvar: '$myInputDocVariable'}, pipeline: [ { $match: { $expr: { $and: [ { $eq: [ "$varFromCommentDocument", "$$myvar" ] }, ] } } }, ], as: "returnedValue" } The query above works fine but the query below does not work as expected. Why is this? Does this mean that

问题 Why do I have to use this code: { $match: { $expr: { <aggregation expression> } } } to match a document using a document input variable as opposed to doing: { $match: { <query> } } ? For example: $lookup: { from: "comments", let: { myvar: '$myInputDocVariable'}, pipeline: [ { $match: { $expr: { $and: [ { $eq: [ "$varFromCommentDocument", "$$myvar" ] }, ] } } }, ], as: "returnedValue" } The query above works fine but the query below does not work as expected. Why is this? Does this mean that

问题 Tried to insert auto increment number for serial number in mongodb using mongoose and nodejs but not working.Where i want to update my code to find solution.If anyone knows please help to find solution. subs.model.js: const mongoose = require('mongoose'); var subscriberSchema = new mongoose.Schema({ _id: {type: String, required: true}, email: { type: String } }, { versionKey: false, collection: 'subscribers' }); module.exports = mongoose.model('Subscribers', subscriberSchema); data.controller

问题 Tried to insert auto increment number for serial number in mongodb using mongoose and nodejs but not working.Where i want to update my code to find solution.If anyone knows please help to find solution. subs.model.js: const mongoose = require('mongoose'); var subscriberSchema = new mongoose.Schema({ _id: {type: String, required: true}, email: { type: String } }, { versionKey: false, collection: 'subscribers' }); module.exports = mongoose.model('Subscribers', subscriberSchema); data.controller

问题 Tried to insert auto increment number for serial number in mongodb using mongoose and nodejs but not working.Where i want to update my code to find solution.If anyone knows please help to find solution. subs.model.js: const mongoose = require('mongoose'); var subscriberSchema = new mongoose.Schema({ _id: {type: String, required: true}, email: { type: String } }, { versionKey: false, collection: 'subscribers' }); module.exports = mongoose.model('Subscribers', subscriberSchema); data.controller

问题 I have these 2 collections: power_usages_month { "_id" : ObjectId("5f1029d4a25f8180630896ad"), "device_sn" : "ST9L0CY4A2AVY7HFWWUE", "switch_id" : ObjectId("5f0ec823580cf34423ccb13d"), "name" : "Lampu", "current" : 0.6299, "time_minutes" : NumberInt(1040), "created_at" : ISODate("2020-07-16T17:20:04.403+0000"), "updated_at" : ISODate("2020-07-16T17:20:04.403+0000") } { "_id" : ObjectId("5f1029d4a25f8180630896ae"), "device_sn" : "ST9L0CY4A2AVY7HFWWUE", "switch_id" : ObjectId(

问题 I have these 2 collections: power_usages_month { "_id" : ObjectId("5f1029d4a25f8180630896ad"), "device_sn" : "ST9L0CY4A2AVY7HFWWUE", "switch_id" : ObjectId("5f0ec823580cf34423ccb13d"), "name" : "Lampu", "current" : 0.6299, "time_minutes" : NumberInt(1040), "created_at" : ISODate("2020-07-16T17:20:04.403+0000"), "updated_at" : ISODate("2020-07-16T17:20:04.403+0000") } { "_id" : ObjectId("5f1029d4a25f8180630896ae"), "device_sn" : "ST9L0CY4A2AVY7HFWWUE", "switch_id" : ObjectId(

问题 My objective is to query mongoDB for a subset of an array within an array. For example, in the 'whole Data Set' (below), I would like to get all of the chorePerson records that have a personID of '5c6e3c74b9f5ed0016b00577' Whole Data Set [ { "_id": "5c7464a26b47a13470411031", "affiliation": "liss_family", "year": 2019, "weekNumber": 9, "chart": [ { "chorePerson": [ { "_id": "5c7464a26b47a13470411054", "person": "emily", "personID": "5c6e3c74b9f5ed0016b00577", "chore": "Catbox", "choreID":