Questions tagged [mongodb]
All versions of MongoDB - a scalable, high-performance, open source, document-oriented database.
2,265
questions
0
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4 views
Significance of $$ in MongoDB
I was recently given this snippet of code that generates an arbitrary document in MongoDB. I've never encountered $$ in Mongo before and I'm curious about its significance.
All I know is that if I run ...
0
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0answers
5 views
Failed global initialization: FileRenameFailed: Could not rename preexisting log file
I get this error while trying to launch mongo deamon.
CONTROL [main] Failed global initialization: FileRenameFailed: Could
not rename preexisting log file
"/var/lib/mongodb/log/mongod.log" ...
0
votes
0answers
19 views
How to specify a sync source when adding a new member to a MongoDB replicaset?
Recently we had a machine physically destroyed, so our replicaset is now: Primary - Secondary - Arbiter (250G on disk, 20G (70hrs) oplog).
So, I'm trying to add a new member (4.4.10) to the replicaset ...
0
votes
1answer
12 views
Mongo node with smaller priority has not stepped out
I have a three nodes replica and I prefer a 10.0.0.5 as a primary. I have just realized during a performance test that 10.0.0.2 is primary instead. I thought it should have step out automatically ...
0
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0answers
22 views
MongodB CPU and memory utilization is low yet queries taking time to execute
I have 3 replica set instances running on different machines. Primary has CPU utilization of 20% and memory usage of 50% yet sometimes there are spike in in random queries which takes several seconds ...
0
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0answers
7 views
Query trajectories that intersect two regions in pymongo
Consider a mongo db where each document corresponds to a spatial trajectory. That is, there is a field that contains an array for each document. Each array is a sequence of latitude/longitude pairs ...
0
votes
2answers
14 views
can we use one arbiter server in two different replica sets of MongoDB?
can we use one arbiter server in two different replica sets of MongoDB?
I had one replica set with
one master
one slave and
one arbiter server
so want to use the same arbiter server in another replica ...
0
votes
1answer
20 views
Unable to join arbiter to a replica set
I'm trying to add a arbiter to replica set.
Unable to join arbiter to a replica set.
port is listening -
netstat -an | grep PORT
tcp6 0 0 :::PORT :::* ...
0
votes
1answer
8 views
MongoDB TLS unable to get issuer certificate
I'm setting up a MongoDB server, and wanted to use TLS from a proper CA and DNS.
I got a domain name and put an A record in, linking to my server. Afterwards, I applied for a SSL certificate on ...
-1
votes
1answer
25 views
Creating a copy of a mongodb replica set
I have a mongodb replica set (1 primary, 2 secondary instances): vm1, vm2, vm3.
I had a need for a second replica set so I created a copy of the above vms: vm4, vm5, vm6.
After booting up vms[4-6] ...
0
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0answers
15 views
GroupBy with count array in MongoDB
I have a collection and object where this object has a list of objects as following:
{
"_id": {
"$oid": "615617f5b0cd1765b7ba21c1"
},
"response": {
&...
0
votes
1answer
22 views
Mongodb continuous schedule and cancel catchup takeover on replica set member
We have a mongodb 4.2 (stable branch) replica set with three members. It was working for several months without problems. Yesterday one of the secondary members started to do very strange things.
I ...
0
votes
1answer
72 views
MongoDB in M1 Mac: 'mongod' command doesn't work
I'm totally new to mongodb and has no knowledge about it at all.
So I just followed installation guides in the internet, but after installation 'mongod' command doesn't work and shows these lines...
{&...
0
votes
1answer
39 views
parse json into a relational database or use a NoSQL?
I am retrieving a JSON file from an API which size varies between 100kb to 7mb. The structure of the response is:
I initially thought in storing the response in a relational database, with the ...
0
votes
0answers
9 views
Track large update process
I need to remove FirstName and LastName nodes from all documents in collection.
The thing is that there are 150M records in it.
I plan to use simple code
db.collname.updateMany({}, { $unset: { "...
0
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0answers
28 views
aggregation with group by, inner join and nested conditions in MongoDB
First of all I am sorry if this is a basic question, I am new to queries in MongoDB. Well, what I need is to find the latest registers for a worker in my WorkerLocationContext document and the latest ...
0
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0answers
21 views
Downsides of creating new collections for the same data in mongodb
My app saves alot of data from different companies on the same format, is it better perfomance wise to have a single collection and separate them by a companyId key or to have multiple collections ...
1
vote
2answers
41 views
Best way to study a new type of database if you are experienced in another type
Does anyone have a good approach to learning a new type of database when they already are proficient in another one? I have thought about writing notes to myself about how to do various tasks that I ...
0
votes
0answers
26 views
Unable to connect to Mongodb database using the Mongodb compass
I have created a mongoDB database on DigitalOcean, then I try to establish a connection to the database using MongoDB Compass. However, when I try to do so, "connect ECONNREFUSED 143.198.217.148:...
0
votes
1answer
39 views
mongodb write issues
We have 5node replicaset , in which 2 servers are in Jacksonville datacenter and 2 servers are on Atlanta datacenter and an arbiter . I had brought down the Atlanta servers , but the write operations ...
0
votes
1answer
22 views
Is ObjectId as shard key unique across shards or just within a shard?
In my sharded cluster of version 4.2, one collections is sharded on _id where _id is just a default ObjectId.
I'm seeing multiple documents with same _id on different shards' primaries.
When I specify ...
0
votes
1answer
25 views
How to access two different databases with different admin databases in MongoDB that are hosted on the same server
I have 2 databases. Suppose first DB is X and second DB is Y. X has its own admin DB and Y has its own admin DB. Both X and Y are hosted on the same server.
I want to pull out data from both the DB's ...
1
vote
1answer
85 views
MongoDB - Slow aggregate query
It takes around 6min to get the result from MongoDB, when I use the following aggregate query.
db.barcodes.aggregate([
{
$lookup: {
from: 'company',
localField: '...
0
votes
2answers
29 views
Not able to shard collection
I have enabled sharding using the below commands.
mongos> use news
switched to db news
mongos> sh.enableSharding("news");
{
"ok" : 1,
"$clusterTime" : {
...
0
votes
0answers
15 views
Does MongoDB client drivers reconnect after restarting from shutting down?
For example, suppose there is an app connected to a mongos, and the mongos instance shutdown. The queries to the MongoDB failed, and after sometime, the mongos restarted.
Does the client driver ...
0
votes
1answer
44 views
Why insert statements get slow when having too many indexes?
I am having a slowness in my insert statements when working with MongoDB, and when I did a quick investigation, I though this might happened because the table has 11 indexes. Plus, I know that when I ...
0
votes
0answers
61 views
How to create an index on MongoDB for Multiple Fields
I am looking to create an index on MongoDB, am relatively new to this type of DBMS, have looked in the MongoDB log and noticed that its doing a COLLSCAN which from reading online can indicate that an ...
0
votes
0answers
29 views
How to smooth high write peaks (every 60s) in a write-heavy MongoDB?
We have a MongoDB cluster (3-member replica set, no sharding), operated on AWS. The application has a very write-heavy pattern.
While the average write IOPS stay under 5k, most writes occur in peaks ...
0
votes
0answers
18 views
Enable username and password authentication on mongodb sharded cluster
I have a mongodb cluster(1 mongos, mongo config replica set with 2 members, 1 shard with 3 members) and I have enabled internal authentication in config replica set. Also my backend code connects to ...
0
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0answers
15 views
premission denied: mongoDB not working when calling mongod
when i try to start mongodb in vscode as:
$ mongod
it replay:
bash: /home/linuxbrew/.linuxbrew/bin/mongod: Permission denied
why and how to fix it?
0
votes
0answers
12 views
Mongostat not displaying inserts to time series?
I'm using MongoDB 5.0.2 and mongostat 100.5.0, and I notice that I'm not able to monitor insert for time series, or at least they do not show up. Is there either some way to enable this, or to monitor ...
0
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0answers
13 views
MongoDB Index Restore Failure Since I Upgraded from 4.2 to 4.4
Steps to reproduce
After upgrading from 4.2 to 4.4, take backup using mongodump
Now restore backup
On some collections, I am getting following {"alternate":"non-ignorable", "...
0
votes
2answers
22 views
How to organize MongoDB replicaset backup and alerting
I have a running MongoDb replicaset consisting of 2 replicas and 1 master nodes. Recently I noticed that my master gone and automatic failover took action and changed master, however I wasn't aware of ...
0
votes
0answers
17 views
MongoDB / WiredTiger indexes became much larger after dump / restore
I've done a migration from one replicaset to another. The OS and mongo version is the same 4.4.8 (maybe initial creation of prod03 was 4.0 or 4.2 with updates to 4.4.x).
Now I see substantial growth ...
0
votes
1answer
31 views
Incorrect migration of an object from Firebase to MongoDB
I am in the process of migrating a database from Firebase to MongoDB and am facing a problem. Here is such an object I have stored in the FB:
"logs": {
"2021-05-24": {
&...
0
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0answers
31 views
document db tree structure - is it valid to have both child and parent references in each node?
I'm in the process of building a tree structure, which should support the following requirements:
It should be possible to find the root of the tree
The tree will most often be traversed from root-&...
0
votes
1answer
19 views
In MongoDB ReplicaSet, does a priority 0 node (hidden, delayed, etc) have to have the same Oplog size as the nodes that can become primary?
I understand the Oplog collection in MongoDB replica set. A bigger Oplog means a bigger recovery window when a data bearing node goes down.
However for nodes that can never be primary, is the Oplog ...
0
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0answers
16 views
How bulk query mongodb where each filter has its own limit?
I'm trying to create a search algorithm that will return more diverse results based on one common field in my "Articles" collection in my MongoDB.
My "Articles" schema basically ...
2
votes
0answers
28 views
How does MongoDB solve the concurrency issue for meeting room booking problem? [closed]
When implementing a typical meeting room booking system with RDBMS, there will be two operations:
-- Check for any existing bookings that overlap with the period of noon-1pm
SELECT COUNT(*) FROM ...
0
votes
1answer
36 views
why it is not recommended to run mongod process as root user as per documentation
Why is it not recommended to run mongod process as root as per the documentation?
Is it only security that we run it as a non root user ?
Will running as root cause any specific issues like Out of ...
0
votes
0answers
30 views
Why MongoDB Shard becomes slow in data insertion over larger amount data inserted?
General
We generate about 10GB of records each day. Each record is composed of four columns: id,A,B,C.
The column id must be unique but will be never queried. Columns A,B,C must be indexed (or some ...
1
vote
1answer
27 views
issues after mongorestore completed
Once mongorestore is completed.
Most of the times one of the node will not be able to catch the
primary after the restore is done on primary and that becomes too stale to replicate from Primary.
What ...
0
votes
1answer
24 views
Mongodb Discrepancy between space actually used and space available
I'm not sure if this has already been asked but I'm facing a weird issue in MongoDB 4.2.8(Standalone).
We have a single collection running which uses a TTL index to delete all documents that are older ...
0
votes
0answers
17 views
MongoDB - Grant permission over one collection that exists on all databases
I have several databases on my MongoDB, all of them have or will have a collection called _schema. Currently, I'm granting permissions like this:
db.grantRolesToUser("userA",[
{"role&...
0
votes
1answer
61 views
How does MongoDB Treat Mixed Types?
I'm messing around with mongodb and noticed I can create mixed data types.
db.getSiblingDB("bermuda").getCollection("test").insertOne({
"profile": {
"t1&...
0
votes
0answers
29 views
Help find a usecase to understand sql vs nosql issue [duplicate]
I have very little background in SQL (one pet project with PostgreSQL that demonstrated only basic queries up to joins) and no experience at all with NoSQL. I understand that there are many DB ...
0
votes
0answers
13 views
recreate available connections = zero condition on mongodb replset
Default ulimit for mongo user is 1024, and max connections that mongo uses is 818 which is 80% of 1024. When the next connection reaches 819, mongod will cease and will not accept anymore clients ...
0
votes
0answers
24 views
Robo 3T able to bypass MongoDB auth=true
I used robo 3t to login to a database and was surprised that I was able to write on the collection despite having a read only role, by adding a document via the GUI or sending commands through Robo 3T....
0
votes
1answer
79 views
How do I restore a database using MongoDB 5.0 CLI?
I've just installed the MongoDB version 5.0 CLI tools on my workstation.
But now when I go to restore a database like I've always done I get an error:
mongorestore
mongorestore : The term '...
0
votes
0answers
27 views
How to convert array objects with object ids as one of key value pair to string?
I have the following JSON,
How to convert an array of objects with object ids to string in MongoDB using aggregation query?
{
"_id": ObjectId("60e41eb7335412757cc6cb9a"),
"...
