mongodb-query

问题 I have documents like this one at collection x at MongoDB: { "_id" : ... "attrs" : [ { "key": "A1", "type" : "T1", "value" : "13" }, { "key": "A2", "type" : "T2", "value" : "14" } ] } The A1 and A2 elements above are just examples: the attrs field may hold any number of array elements. I'd need to access concurrently to the attrs array from several independent clients accessing to MongoDB. For example, considers two clients, one wanting to change the value of the element identified by key

问题 Can you perform a MongoDB covered query for two fields, for example db.collection.find( { _id: 1, a: 2 } ) without having a compound index such as db.collection.ensureIndex( { _id: 1, a: 1 } ) but instead having only one index for _id (you get that by default) and another index for field "a", as in db.collection.ensureIndex( { a: 1 } ) In other words, I'd like to know if in order to perform a covered query for two fields I need a compound index vs. needing only two single (i.e., not compound)

问题 I have just started to play with MongoDB and have some questions about how I update my documents in the database. I insert two documents in my db with db.userscores.insert({name: 'John Doe', email: 'john.doe@mail.com', levels : [{level: 1, hiscores: [90, 40, 25], achivements: ['capture the flag', 'it can only be one', 'apple collector', 'level complete']}, {level: 2, hiscores: [30, 25], achivements: ['level complete']}, {level: 3, hiscores: [], achivements: []}]}); db.userscores.insert({name:

问题 I have time series data in mongodb as follows: { "_id" : ObjectId("558912b845cea070a982d894"), "code" : "ZL0KOP", "time" : NumberLong("1420128024000"), "direction" : "10", "siteId" : "0000" } { "_id" : ObjectId("558912b845cea070a982d895"), "code" : "AQ0ZSQ", "time" : NumberLong("1420128025000"), "direction" : "10", "siteId" : "0000" } { "_id" : ObjectId("558912b845cea070a982d896"), "code" : "AQ0ZSQ", "time" : NumberLong("1420128003000"), "direction" : "10", "siteId" : "0000" } { "_id" :

问题 I have a collection in MongoDB that contains several fields, and is written to by my application server every time a user performs an action. A sort of log-collection. Each document resembles the following pattern, omitting a few irrelevant fields for the sake of brevity: { "_id" : ObjectId("5536727686e09bab576f1c94"), "_user" : ObjectId("5536597b60b2321aadeb8a7c"), "_userAgent" : "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:36.0) Gecko/20100101 Firefox/36.0", "_systemTime" : ISODate("2015-04

问题 I'm trying to filter on an array field which unfortunately doesn't seem to be working correctly. Everything I've read suggests that this should work, and the sort is doing something , just not what I expected and I can't explain it. What I'm trying to achieve is sorting on an array sub-field. I've managed to achieve most of this using the positional operator but I can't work out what the sort is doing. db.getCollection('boards') .find({ "lastVisited.user": "AAA" }, { name: 1, "lastVisited.$"

问题 I have the following scrip in "script.js" conn = new Mongo(); db = conn.getDB("learn"); db.contracts.aggregate([ { $match: { regionCode: '77' } }, { $unwind: '$products' }, { $project: { _id: '$_id', regNum: '$regNum', prodName: '$products.name', prodPrice: '$products.price' } }, { $match: { 'prodName' : 'Water' } } ], {cursor:{}}).result.forEach(printjson); I run it from the command prompt by the following way mongo script.js >> out.txt In file "out.txt" I have the error TypeError: Cannot

问题 I have Following Project Collection Project Collection : [ { Id : 1, name : p1, tasks : [{ taskId : t1, startDate : ISODate("2018-09-24T10:02:49.403Z"), endDate : ISODate("2018-09-26T10:02:49.403Z"), }, { taskId : t2, startDate : ISODate("2018-09-24T10:02:49.403Z"), endDate : ISODate("2018-09-29T10:02:49.403Z"), }, { taskId : t3, startDate : ISODate("2018-09-24T10:02:49.403Z"), endDate : ISODate("2018-09-27T10:02:49.403Z"), }] } ] How to get p1 project's startDate and EndDate depending on

问题 With a MongoDB collection test containing the following documents: { "_id" : 1, "color" : "blue", "items" : [ 1, 2, 0 ] } { "_id" : 2, "color" : "red", "items" : [ 0, 3, 4 ] } if I sort them in reversed order based on the second element in the items array, using db.test.find().sort({"items.1": -1}) they will be correctly sorted as: { "_id" : 2, "color" : "red", "items" : [ 0, 3, 4 ] } { "_id" : 1, "color" : "blue", "items" : [ 1, 2, 0 ] } However, when I attempt to sort them using the

问题 I am using mongotemplate , my collection look like this: { "_id": "theid", "tag": "taga", "somefield": "some value", "fieldC": { "anotherfielad": "more data", "an_array": [ { "a": "abc", "b": 5 }, { "a": "bca", "b": 44 }, { "a": "ddd", "b": 21 } ] } } { "_id": "anotherid", "tag": "taga", "somefield": "some other value", "fieldC": { "anotherfielad": "other more data", "an_array": [ { "a": "ccc", "b": 6 }, { "a": "abc", "b": 99 }, { "a": "ddd", "b": 21 } ] } } I need to get a unique result from