mongodb-query

问题 I have 2 collections (with example documents): reports { id: "R1", type: "xyz", } reportfiles { id: "F1", reportid: "R1", time: ISODate("2016-06-13T14:20:25.812Z") }, { id: "F14", reportid: "R1", time: ISODate("2016-06-15T09:20:29.809Z") } As you can see one report may have multiple reportfiles . I'd like to perform a query, matching a report id , returning the report document as is, plus an additional key storing as subdocument the reportfile with the most recent time (even better without

问题 I'm trying to create an aggregate query using mongotemplate where there's a grouping by date (i.e 2016-03-01) instead of datetime (i.e 2016-03-01 16:40:12). The dateToString operation exists in the mongodb documentation it can be used to extract the date from the datetime using formatting: https://docs.mongodb.org/manual/reference/operator/aggregation/dateToString/ but I get get it to work with mongotemplate - I get a NullPointerException. (my db version is 3.2) List<AggregationOperation>

问题 I have 2 collections: list1 and list2. list1 have some fields and list2 have another fields, including the id referring to list1. I need to do a query to export all items on list1 that have at least one item referring to him on list2. How can I do this? It's something like a join from list1 to list2. I need to run a mongoexport command to generate a csv file. 回答1: The way I do this is to create a short javascript program that will transfer the data you want to export into a new temporary

问题 In MongoDB all documents have a date field, it is a timestamp. There is a lot of data, and I want to get only some part of it, for every interval: e.g. 400ms 1402093316030<---- 1402093316123 1402093316223 1402093316400<---- 1402093316520 1402093316630 1402093316824<---- Is it possible to get every other, or every third result? Or better first document every 400 ms? 回答1: You can do this with the aggregation framework and a little date math. Let's say you have a "timestamp" field and addtional

问题 This is about the new MongoDB C++ Driver (not the legacy one). I can insert a document this way: value Value = document{} <<"Key" <<"Value" <<finalize; cxxClient["db"]["collection"].insert_one(Value.view()); The above code insert a document with 1 field 'Key' of value 'Value'. I can insert string, int, float,... but just can't figure out how to insert ISODate. The new MongoDB C++ Driver should come with more examples in documentation. 回答1: Thanks Styvane, I found it out how! value Value =

问题 Is there's a way to get the size of all the documents that meets a certain query in the MongoDB shell? I'm creating a tool that will use mongodump (see here) with the query option to dump specific data on an external media device. However, I would like to see if all the documents will fit in the external media device before starting the dump. That's why I would like to get the size of all the documents that meets the query. I am aware of the Object.bsonsize method described here, but it seems

问题 I was fortunate enough to get an awesome answer to another SO question Mongo / Mongoose - Aggregating by Date from @chridam which given a set of documents like: { "_id" : ObjectId("5907a5850b459d4fdcdf49ac"), "amount" : -33.3, "name" : "RINGGO", "method" : "VIS", "date" : ISODate("2017-04-26T23:00:00Z"), "importDate" : ISODate("2017-05-01T21:15:49.581Z"), "category" : "Not Set", "__v" : 0 } { "_id" : ObjectId("5907a5850b459d4fdcdf49ba"), "amount" : -61.3, "name" : "Amazon", "method" : "VIS",

问题 I run a java program which is a thread executor program that inserts thousands of documents to a table in mongodb. I get the following error Exception in thread "pool-1-thread-301" com.mongodb.MongoWaitQueueFullException: Too many threads are already waiting for a connection. Max number of threads (maxWaitQueueSize) of 500 has been exceeded. at com.mongodb.PooledConnectionProvider.get(PooledConnectionProvider.java:70) at com.mongodb.DefaultServer.getConnection(DefaultServer.java:73) at com

问题 Using $sort and $group in one aggregation query behaving strangely. Test data: db.createCollection("test"); db.test.insert({ ts : 100, category : 1 }); db.test.insert({ ts : 80, category : 1 }); db.test.insert({ ts : 60, category : 2 }); db.test.insert({ ts : 40, category : 3 }); So when sorting it by ts all looks good, but when I use both $sort and $group result goes in a wrong order. Query: db.test.aggregate([ { $sort : {ts: 1} }, { $group:{"_id":"$category"} } ]); And the result in reverse

问题 In my model definition, I have: appFeatures: [{ name: String, param : [{ name : String, value : String }] }] I want to set default value to appFeatures, for example: name: 'feature', param: [{name:'param1',value:'1'},{name:'param2',value:'2'}] I tried to do it by appFeatures : { type : Array , "default" : ... } But its not working, any ideas? Thanks 回答1: Mongoose allows you to "separate" schema definitions. Both for general "re-use" and clarity of code. So a better way to do this is: //