mongodb-query

问题 I have the following document structure { "_id" : 1, "prices" : { "100" : [ 5.67, . . 1.7, ], "101" : [ 4.67, . . 1.4, }, "v" : 2 } We need to get the last value from each of the fields "100" and "101", e.g 1.7 & 1.4, using mongodb v3.0.2. Currently we are loading the whole document and then getting the required values in the application. It has become quite a bottleneck as each document may be ~1MB, which for 100s of documents is adding up. We are hoping there is a suitable feature of

问题 db.main.aggregate([ { $lookup: { from: "history", localField: "history_id", foreignField: "history_id", as: "History" } }, { $project: { "History": { $filter: { input: "$History", as: "his", if: { $eq: [ "5e4a8d2d3952132a08ae5764", "$$his.user_id" ] }, then: { cond: { $and: [ { $lt: [ "$$his.date", "$date" ] }, { $eq: [ "5e4a8d2d3952132a08ae5764", "$$his.user_id" ] } ] } }, else: {} } }, data: 1, history_id: 1, sender_id: 1, text: 1, date: 1 } }, { $unwind: "$History" } ]) MongoPlayground

问题 Considering I have the following documents in a collection (ignoring the _id ) : [ { "Id": "OP01", "Sessions": [ { "Id": "Session01", "Conversations": [ { "Id": "Conversation01", "Messages": [ { "Id": "Message01", "Status": "read", "Direction": "inbound" }, { "Id": "Message02", "Status": "delivered", "Direction": "internal" }, { "Id": "Message03", "Status": "delivered", "Direction": "inbound" }, { "Id": "Message04", "Status": "sent", "Direction": "outbound" } ] }, { "Id": "Conversation02",

问题 What is difference between "size" and "storageSize" displayed by Mongo stats() function? Which one shows the actual size on disk for a particular collection? Refer sample data returned by command db.getCollection('temp_collection').stats() {"ns" : "DB1.temp_collection", "count" : 1035219, "size" : 1186, "avgObjSize" : 1202, "storageSize" : 177, "capped" : false, "wiredTiger" : } 回答1: in simple words: size refers for logical allocation (this is seen by database engine) storageSize refers for

问题 What is difference between "size" and "storageSize" displayed by Mongo stats() function? Which one shows the actual size on disk for a particular collection? Refer sample data returned by command db.getCollection('temp_collection').stats() {"ns" : "DB1.temp_collection", "count" : 1035219, "size" : 1186, "avgObjSize" : 1202, "storageSize" : 177, "capped" : false, "wiredTiger" : } 回答1: in simple words: size refers for logical allocation (this is seen by database engine) storageSize refers for

问题 What is difference between "size" and "storageSize" displayed by Mongo stats() function? Which one shows the actual size on disk for a particular collection? Refer sample data returned by command db.getCollection('temp_collection').stats() {"ns" : "DB1.temp_collection", "count" : 1035219, "size" : 1186, "avgObjSize" : 1202, "storageSize" : 177, "capped" : false, "wiredTiger" : } 回答1: in simple words: size refers for logical allocation (this is seen by database engine) storageSize refers for

问题 What is difference between "size" and "storageSize" displayed by Mongo stats() function? Which one shows the actual size on disk for a particular collection? Refer sample data returned by command db.getCollection('temp_collection').stats() {"ns" : "DB1.temp_collection", "count" : 1035219, "size" : 1186, "avgObjSize" : 1202, "storageSize" : 177, "capped" : false, "wiredTiger" : } 回答1: in simple words: size refers for logical allocation (this is seen by database engine) storageSize refers for

问题 How do I have autoincrement ids in mongoose? I want my ids to start like 1, 2, 3, 4, not the weird id numbers mongodb creates for you? Here's my schema: var PortfolioSchema = mongoose.Schema({ url: String, createTime: { type: Date, default: Date.now }, updateTime: { type: Date, default: Date.now }, user: {type: Schema.Types.ObjectId, ref: 'User'} }); 回答1: Use mongoose-auto-increment: https://github.com/codetunnel/mongoose-auto-increment var mongoose = require('mongoose'); var autoIncrement =

问题 How do I have autoincrement ids in mongoose? I want my ids to start like 1, 2, 3, 4, not the weird id numbers mongodb creates for you? Here's my schema: var PortfolioSchema = mongoose.Schema({ url: String, createTime: { type: Date, default: Date.now }, updateTime: { type: Date, default: Date.now }, user: {type: Schema.Types.ObjectId, ref: 'User'} }); 回答1: Use mongoose-auto-increment: https://github.com/codetunnel/mongoose-auto-increment var mongoose = require('mongoose'); var autoIncrement =

问题 I have a query and when I use a $group a error shows "the field "$name must be an accumulator object", if if remove the filed "$name" all works well and i have tried to use only "name" instead of "$name" and the error continues. User.aggregate([ { $match: { "storeKey": req.body.store } }, { $group: { "_id": "$_id", "name": "$name", "count": { "$sum": 1 }, "totalValue": { "$sum": "$value" } } }, { $sort: sort }, { $skip: req.body.limit * req.body.page }, { $limit: req.body.limit } ])... 回答1: