CODEWITHSUNDEEP
mongodb
treecoder
treecoder

Reputation: 45081

Is there a limit to the number of documents in MongoDB?

This is related to my last question.

We have an app where we are storing large amounts of data per user. Because of the nature of data, previously we decided to create a new database for each user. This would have required a large no. of databases (probably millions) -- and as someone pointed out in a comment, that this indicated wrong design.

So we changed the design and now we are thinking about storing each user's entire information in one collection. This means one collection exactly maps to one user. Since there are 12,000 collections available per database, we can store 12,000 users per DB (and this limit could be increased).

But, now my question is -- is there any limit on the no. of documents a collection can have? Because of the way we need to store data per user, we expect to have a huge (tens of millions in extreme cases) no. of document per documents.

The app is a specialized inventory control system. Each user has a large no. of little pieces of information related to them. Each piece of information has a category and some related stuff under that category. Moreover, no two collections need to see each other's data -- hence an index that touch more than one collection is not needed.

Upvotes: 1

Views: 4797

Answers (2)

Ian Mercer
Ian Mercer

Reputation: 39277

If you are indexing by some field that has content that's common across all the users you'll get a significant saving in total index size by having a single collection with one index.

Index size is often the limiting factor not total database size when it comes to performance.

Craigslist put 2+ billion documents in MongoDB so that shouldn't be an issue if you have the hardware to support it and aren't being inefficient with your indexes.

If you posted more of your schema here you'd probably get better advice.

Upvotes: 0

Eve Freeman
Eve Freeman

Reputation: 33145

To adjust the number of collections/indexes you can have (~24k is the limit--~12k is what they say for collections because you have the _id index by default, but keep in mind, if you have more indexes on the collections, that will use namespace up as well), you can use the --nssize option when you start up mongod.

There are plenty of implementations around with billions of documents in a collection (and I'm sure there are several with trillions), so "tens of millions" should be fine. There are some numbers such as counts returned that have constraints of 64 bits, so after you hit 2^64 documents you might find some issues.

Upvotes: 2

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