1

I read Mongodb using wired tiger storage engine has MVCC and it may create multiple versions of the same document for better concurrency. (Mongo using MMAPv1 storage engine doesn't have MVCC. This question is for Mongo with wired tiger storage engine.)

If we frequently update a large document (> 1MB), will there be multiple versions of that document in cache as well as on disk? When are the older versions get deleted? Is there any in place update in Mongodb?

I will be maintaining some big documents in a collection and the document looks like an inverted index. Its schema is like {"userid" : ["follower1", "follower2", "follower3",....]} The list of followers may contain 100,000+ followers. Anytime, new follower may be added or old follower may be deleted from the list. How will be the performance for adding a new follower to the list of followers? If within a second the follower list is updated 10 times in the document, will there be 10 copies of the document at least for some time?

Nipun Talukdar
  • 4,975
  • 6
  • 30
  • 42
  • 2
    That looks like a bad design, you shouldn't embed arrays of over 100,000 elements inside a document. Instead you should split it out in two separate collections. Can a userid also be a follower ? – Alex Dec 17 '15 at 13:19
  • Yes. A userid can also be a follower. – Nipun Talukdar Dec 17 '15 at 13:22

0 Answers0