CODEWITHSUNDEEP
mongodbmongodb-java
Galaxy
Galaxy

Reputation: 863

How to frequently Update all the documents with a random number in mongodb

I have created the following schema in MongoDB:

{
    "_id" : ObjectId("52d5c71be4b0a5cd12da5e8b"),
    "edges" : [
        {
            "edge_id" : "0",
            "dst" : NumberLong(1),
            "score" : ***Numeric Value***

        },
        {
            "edge_id" : "1",
            "dst" : NumberLong(6),
            "score" : ***Numeric Value***

        }
    ],
    "src" : NumberLong(0)
}

The above MongoDB collection has millions of records. My requirement is:

  1. Update the Score field with the random numeric value.
  2. All the updates should complete in few seconds (1–10 secs.).
  3. Run the above update procedure infinitely.

I would like to perform the above task either using MongoDB or using a combination of MongoDB and Java.

What is the best way to perform the above task?

Upvotes: 1

Views: 1531

Answers (2)

Jeff Tian
Jeff Tian

Reputation: 5893

With mongodb, we can update multiple documents by (for example)

db.getCollection('users').update({
    username: {$eq: null}
}, {
    $set: {
            username: 'not_set_yet'
    }
}, {
    multi: true
})

If you use Typegoose or mongoose then you can add a pre hook to listen the update event, for example in typegoose:

import {pre} from 'typegoose'

@pre<User>('save', function(next: HookNextFunction) {
  // Caution! Do not use arrow function here, otherwise the `this` variable would // be point to global instead of
  // this model !
  this.username = this.username === 'not_set_yet' ? generateARandomUserName() : this.username

  next()
})

So by combining the 2 things:

  • set multi to true in the update statement
  • set a update hook

it suppose to work so that worth a try.

Upvotes: 0

WiredPrairie
WiredPrairie

Reputation: 59763

There is no way in MongoDB currently to update a batch of documents at a single time. You can update multiple documents with the same value only. So, you'd need to, for each document, individually set the score field. Also, you apparently have an array, so, you'd need to update using the positional array notation the specific score field (or set the entire array).

This will not complete in seconds. It's simply too much activity (disk and network).

If you explained more of what your trying to accomplish with this update, then there may be a better solution. Given the frequency of updates and the fact that the data is constantly changing, I'd suggest that this data structure only be kept in memory for example, and possibly served to "clients" via a web service or other transfer mechanism.

Update:

Given your requirements, I'd suggest that this is not a good fit for MongoDB (or maybe for any disk-backed database for that matter).

Upvotes: 1

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