MongoDB is a scalable, high-performance, open source, document-oriented database. It supports a large number of languages and application development platforms. Questions about programming should be asked on http://stackoverflow.com.

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Failing to ensureIndex on sharded Mongo

I run a mongoDb, sharding it on 4 different shards (+ 1 router and + 1 config). Sometime ago I had to replace a shard, and everything went ok. But now, every time I run: db.summoners.ensureIndex( { ...
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24 views

Mongo DB accessesNotInMemory issue with RAM size

I am using Mongo Replica set and it seems to be working fine but when i check db.serverStatus i saw that there are lots of accessesNotInMemory for all The DBs in my mongo instance. I checked MY RAM ...
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12 views

Mongo 3.0 release for Cent OS

Can any one tell me When Mongo team will release 3.0 production release. Also will it be available for cent OS as we are shifting g our production boxes from RHEL 6 to cent OS and on Mongo Download ...
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14 views

How to create and select entities in MongoDB?

I'm a newbie in MongoDB and I'm trying to understand how to create objects there and how to select them in comparison with relational databases. So I need an example how to perform these things. ...
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Mongodb developer ROLE [closed]

is there or will there be a market with job role as mongodb developer like oracle developer or sql server developer. pure database developer without any need to code in java or perl or python.. Or ...
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8 views

Error while doing in replicaset in windows (mongodb)

I tried doing the replicatset in windows, but im getting the below error. I checked the mongo process and killed the existing process. Even though the error exists. help me on this pls Thx ...
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How the statement based replication works internal on secondary node of mongodb?

Mongodb supports statement-based-replication. Would like to know, how the statement based replication converts the code internally on secondary node of mongodb. Is that working related to the ...
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28 views

Sorting on compound Indexes

This may be a novice question but could it be possible query here. If I have a compound Index as { a: 1, b: 1, c: 1, d: 1 } Is this query possible? db.data.find( { a: {$gte:1,$lt:2}, b: { $gt: 3} ...
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Mongodb schema design validation

I am building an app which allows users to do some "tasks" to earn points. The "tasks" are part of a "campaign" which themselves are a part of "brands". I am confused about the schema for storing the ...
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9 views

MongoDB sharding one collection on single server (2 drives)

I have one single server with two drives (SSD 256GB, HDD 1 TB). What I want to do is to store the newest documents in collection on SSD. Older documents can be stored in HDD drive. Is it possible in ...
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Can we resize a already capped collection in mongo db [duplicate]

I have a capped collection whose initial size i gave 3 GB. Can I modify its size again i mean reducing or increasing both way as per need? is there any command to do it. ...
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+50

MongoDB: co-locate the mongos process on application servers

I would like to ask a question about a best practice described in this document: http://info.mongodb.com/rs/mongodb/images/MongoDB-Performance-Best-Practices.pdf Use multiple query routers. Use ...
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Good way to store daily train data in MongoDB

I am preparing to collect large amounts of information about trains in my country. Each train in my country has a number. I've already collected all of these numbers. There are about 4000 of them. ...
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20 views

MongoDB auto-failover: election doesn't happen

I have the following working replica set: { "_id" : "repl1", "version" : 6, "members" : [ { "_id" : 0, "host" : "hostA", ...
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10 views

Error running --eval mongodb command

I tried to run javascript (js) file to get shard's config server information, it runs fine in mongo shell but as result is too large to analyse on command prompt, i tried to save the output in a file ...
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21 views

MongoDB stops responding after 2 days of working

I've written small application in Python (I used Twisted). Program receives data and writes it to MongoDB. Every 2 days MongoDB stops responding: 2015-02-11T10:47:20.918+0100 [initandlisten] can't ...
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1answer
25 views

Extremely long startup time for MongoDB server

I have a MongoDB Server with just over 2 million documents in one collection. Individual documents can contain large amounts of data (some are several megabytes each) but none of that data is in ...
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The MondoDB.org “Category Hierarchy” Example

I am creating an MVP app for a client but I am skilled in iOS mainly with only some DB experience. I'm using MongoDB. The schema is for a Product Catalog for small markets. The client wants a ...
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8 views

Mongo find query is not using indexes in java code but working on mongo cosole

I found a strange issue. When i run mongo query from my java code with explain true it does not show me index used in the query but when i run it using mongo console it works fine . ...
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1answer
11 views

What “fromRouter” option means on MongoDB aggregations?

Recently i notice that a parameter fromRouter" : true exists on mongoDB aggregations. I search the MongoDB documentation and google for it, but i didn't found anything about it. Can anyone explain ...
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2answers
37 views

Why does mongodb require three config servers

The official mongodb documentation states to use three config servers. They say its for redudancy, because 1 server would be a point of failure.... but why not 2? in a production sharded cluster, if I ...
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19 views

Saving String as unique number in Mongo

I have a field in my collection which is a String in nature. When i run aggregation for this field in data it takes considerable time in aggregation. Total 6 million records are in collection which ...
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13 views

MongoDB Sparse Index Query

I have around 40 million records in my collections but some million documents doesn't contain a field "catId". Sample Document : { "_id": ObjectId("5458b1a24669c5c0d66ae658"), "host": ...
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13 views

what model should i use for store detections time series in mongodb?

i have cloud site with many hosts and virtual machines inside of it. I receive from some software many different metrics values regarding vms usage (cpu load,free ram,energy consumption and so on). ...
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1answer
24 views

MongoDB Hashed Shard Keys Selection

I have a DB which holds very simple documents called "Item": {_id:<ObjectId>, playerId:int, isRead:bool, content:string} containing about 80M documents. Each Item belongs to a certain player, ...
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22 views

Data containing list of all the domain names. MongoDB or MySQL?

Data containing list of all the domain names (currently present in the Internet world), along with few attributes (5-6 or maybe 10, each attribute being a column) will be considered as Big Data? ...
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2answers
19 views

MongoDB Disk Usage with Capped Collections

I am using MongoDB using C#. I am currently using only a single server. Since I have to create Table events for MongoDB collections I have created a single replica set(primary). And using ...
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13 views

Installing Mongodb on windows

Does anyone have any adverse experience of running mongodb on windows? What is the recommended platform to run mongodb?
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1answer
11 views

what is default balancing window in MongoDB

I have read about balancing window in MongoDB document. I see mongo tell about how to modify balancing window but I don't see the default of balancing window. I see only one document about chunk size ...
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12 views

Using MongoDB with circular object references

Please forgive me from the beginning. I am brand new to document oriented databases and I am sure that I will need guidance to reform the question in order to get answers. I am looking to use MongoDB ...
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why my data is not being sharded?

I am using mongo 2.6.7 I deploy a sharding cluster follow the guide: http://docs.mongodb.org/manual/tutorial/deploy-shard-cluster/ My sharding cluster include: - two replica sets (one primary + one ...
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1answer
22 views

How to get all documents from a particular chunks in MongoDB?

From mongos log, I got the following message balancer move failed: { chunkTooBig: true, estimatedChunkSize: 408839903, ok: 0.0, errmsg: "chunk too big to move" } from: shard4 to: shard1 I know ...
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14 views

Mongo Memory mapping file size issue

I am witnessing some performance issues in my Mongo Sharded cluster. I checked the serverStatus for the memory uses on my shards This is the output Shard one Primary RAM size 512 GB "mem" : { ...
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MongoDB GridFS delete operation too slow while mongod process takes up 100% CPU

I'm using Python (CPython 2.7.3 on Debian 7.8 amd64) with pymongo driver (version 2.7.2) to connect to a MongoDB (db version v2.4.12) database which has solely been used to store files in a GridFS ...
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1answer
20 views

Setup MongoDB replica servers with different power?

Is it a good practice to setup replicas with the same machine size (wrt. CPUs, RAM, Bandwidth, etc.) or can replicas be based on smaller machines? One usecase might be to have a small non-voting ...
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1answer
50 views

Converting sql into mongodb nosql

I am trying to convert oracle sql into its mongodb equivalent version. create table my_hll as select mod(ora_hash(n), 1024) bucket, max(num_zeroes(trunc(ora_hash(n)/1024)))+1 val from previous_data ...
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26 views

What exactly should I backup in MongoDB when using replica sets?

I have several instances of MongoDB replica set servers with a primary and a failover machine for each replica set. The primary machine makes daily backups by creating an LVM snapshot and copying all ...
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1answer
36 views

Is there any way to change the size of preallocate data file in mongodb?

In mongodb data files are preallocates to a particular size,like first data file .0, the next .1, etc. The first file mongod allocates is 64 megabytes, the next 128 megabytes, and so on, up to 2 ...
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1answer
38 views

mongo: how should I layout my data

I have 2TB of data currently spread across many CSV files that looks like: { 'rec_date': "2010-01-29", 'rec_time': "09:15:00", 'site_no': '46', 'data_owner': '1', 'flow_period': '5', ...
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1answer
62 views

Failing to automatically re-connect to New PRIMARY after a replica set failover , from Mongoose (MongoDB, NodeJS Driver)

I made a simple NodeJS App, with Mongoose as MongoDB Driver. And connected to a mongodb replica set. The App is working fine until I shut down the current primary, When the PRIMARY is down, the ...
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1answer
17 views

Are my MongoDB servers right in setting?

I have a small web site, so I used two servers. A: master 4G Ram, 96G SSD B: slave 2G RAM, 96G SSD The B server is always for backup, no read, no write. In my application, many users can (and will) ...
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30 views

Issue with total count in sharded collection

I am having a collection which is sharded. This collection receives data from a script which is running hourly. On this data we do some aggregation. My issue when we insert data in collection and run ...
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2answers
82 views

Database structure for hierarchical quiz?

I'm doing a personal project where I have a quiz with a number of boolean questions. Each question will have a two answer choices "true" and "false". Based on the selected answer, a new question will ...
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19 views

Config data base showing invalid date for collection modification sharding is stopped

For last few days my sharding is not working and every day i am seeing very slow writes. I tried to drop some existing data to create space. But while dropping some old data i got error and when i ...
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25 views

Repeat statement of ChunkManager: time to load chunks for empty

In my one of the MongoS server i am continuously getting the below chunkManager statement ChunkManager : time to load chunks for empty This is repeating in logs and the day it started insert in my ...
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2answers
92 views

Unable to start Mongodb. Appears to be crashed, if yes, how to recover my data

Below is the error when ouput when I am trying to start my local mongodb. I am unable to start it and after little exploration, I doubt my local db has been crashed. If yes, is there a way to recover ...
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1answer
28 views

mongoexport on 2.0.4

What I'm I missing here? I need data greater that ISODate("2015-01-11T00:39:40.121Z") I know many forums have different answers for the same issue. But non resolved. Need a different point of view ...
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112 views

Can not drop db in sharded environment

I am trying to delete some old dbs in my sharded set up. Step i am taking are : Stop Balancer. Drop Db Start balancer But in some of the DBs i am getting these errors. "errmsg" : "exception: ...
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29 views

Old Mongos servers are found in config database mongo

For some time we are facing issue with our sharded set up as some times one collection randomly stuck on one shard. I have daily db (we create daily database with date) in my application where some ...
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2answers
51 views

Hierarchical data in MongoDB?

I have a question regarding Hierarchical data. Our app shows posts, that are structured inside parents. Here's how it goes: prof->sprof->subject->post (Each prof can contain multiple ...