Question

I have records with:

User id, reputation
1      ,  5
2      ,  8
3      ,  2
4      ,  6

For User id 2, I want to get the user’s reputation and the index of the record using descend ordering of reputation. In this example the index of user 2 is 1, the index of user 4 is 2, etc.

I want the algorithm can process many users(10K at least), so the performance is a concern, please suggest.

Answer 1

You can reverse sort by reputation

db.users.find().sort({"reputation":-1})

For performance of this query, create an index on reputation as:

db.users.ensureIndex({"reputation":-1})