mongodb-query

问题 I want to project a collection applying exporting a value only if a field is inside a range. Sort of: db.workouts.aggregate({ $match: { user_id: ObjectId(".....") } }, { $project: { '20': { $cond: [ {$gt: [ "$avg_intensity", 20]} , '$total_volume', 0] } } }) I need to get the value only if the avg_intensity is inside a certain range. I will then group and sum on the projection result. What I am trying to do is applying a $gt and $lt filter but with no much success. db.workouts.aggregate( {

问题 I have the following MongoDB document: { "_id": ObjectId(), "sku": "V4696-DR-V33", "options": [ { "sku": "8903689984338", "stores": [ { "code": "AND1", "zipcode": "110070", "inventory": -1000 }, { "code": "AND2", "zipcode": "201010", "inventory": -1000 }, { "code": "AND3", "zipcode": "411001", "inventory": -1000 }, { "code": "AND4", "zipcode": " 700020", "inventory": -1000 }, { "code": "AND5", "zipcode": "110015", "inventory": -1000 } ], "price": 2199, "_id": ObjectId(), "size": "14" }, {

问题 I have a collection of 15000 documents. Some documents have sr_no with numeric values and other with absent of sr_no . Now i want to get entries like all documents comes first which has sr_no with asc then all others. I tried .find().sort({sr_no:1}) but it return all null entries first then asc with sr_no . This question seems too close with duplicate. But slightly defer with numeric key. I answered it with hack below. 回答1: I used a dirty hack for this. MongoDB doc says that they have

问题 I have this schema where I validated the elements of array book , but I don't know how to validate the array itself. var DictionarySchema = new Schema({ book: [ { 1: { type: String, required: true }, 2: String, 3: String, c: String, p: String, r: String } ] }); For example, I would like to put the book array as required. Any help? 回答1: You can use a custom validator to do this. Simply check that the array itself is not empty: var mongoose = require('mongoose'), Schema = mongoose.Schema;

问题 i am new to mongodb and stack overflow. I want to know why on mongodb collection ID is of 24 hex characters? what is importance of that? 回答1: Why is the default _id a 24 character hex string? The default unique identifier generated as the primary key ( _id ) for a MongoDB document is an ObjectId. This is a 12 byte binary value which is often represented as a 24 character hex string, and one of the standard field types supported by the MongoDB BSON specification. The 12 bytes of an ObjectId

问题 Consider the below Mongo index strategy and the query, Index: db.collec.ensureIndex({a:1,b:1,c:1}); Query: db.collec.find({"a":"valueA"},{"_id":0,"a":1,"c":1}).sort({"c":-1}).limit(150) The explain on the above query returns: /* 0 */ { "cursor" : "BtreeCursor a_1_b_1_c_1", "isMultiKey" : false, "n" : 150, "nscannedObjects" : 178, "nscanned" : 178, "nscannedObjectsAllPlans" : 279, "nscannedAllPlans" : 279, "scanAndOrder" : true, "indexOnly" : true, "nYields" : 0, "nChunkSkips" : 0, "millis" :

问题 With Spring-Data, you can use the @Document annotation to specify which collection to save the object to. Say I have two classes, Student and Teacher, both persisted into the people collection. When I execute the following code: mongo.find(new Query(), Teacher.class); the result contains both Student and Teacher. Looking in the data created by Spring-Data, each document contains a "_class" field which indicate which class it is persisted from. This is field not used in find as an filter to

问题 I'm using MongoDB 3.2 and MongoDB Java Driver 3.2. I have an array of a couple of hundreds of updated documents which should be now saved/stored in MongoDB. In order to do that, I iterate over the array and call for each document in this array the updateOne() method. Now, I want to re-implement this logic with a bulk update. I tried to find an example of bulk update in MongoDB 3.2 with MongoDB Java Driver 3.2. I tried this code: MongoClient mongo = new MongoClient("localhost", 27017); DB db =

问题 How i can find length of each item in a "mol" list: For example if I am looking for "versionA" : "2.1.2" I expect ot get following result: {"project" : "A", "scene" : 13455312, mol:[3,2,1]}, {"project" : "B", "scene" : 13455344, mol:[3,3,3]} My data: { "project" : "A", "scene" : 13455312, "versionA" : "2.1.2", "versionB" : "2.1.9", "mol" : [ {"data" : [ { "tran" : 'A' }, { "tran" : 'B' }, { "tran" : 'C' }]}, {"data" : [ { "tran" : 'A' }, { "tran" : 'B' }]}, {"data" : [ { "tran" : 'A' }]}] },

问题 I have large collection of documents which represent some kind of events. Collection contains events for different userId. { "_id" : ObjectId("57fd7d00e4b011cafdb90d22"), "userId" : "123123123", "userType" : "mobile", "event_type" : "clicked_ok", "country" : "US", "timestamp" : ISODate("2016-10-12T00:00:00.308Z") } { "_id" : ObjectId("57fd7d00e4b011cafdb90d22"), "userId" : "123123123", "userType" : "mobile", "event_type" : "clicked_cancel", "country" : "US", "timestamp" : ISODate("2016-10