MongoDB 'count()' is very slow. How do we refine/work around with it?

performance mongodb count
Winston Chen picture Winston Chen · Oct 5, 2011 · Viewed 46.2k times · Source

I am currently using MongoDB with millions of data records. I discovered one thing that's pretty annoying.

When I use 'count()' function with a small number of queried data collection, it's very fast. However, when the queried data collection contains thousand or even millions of data records, the entire system becomes very slow.

I made sure that I have indexed the required fields.

Has anybody encountered an identical thing? How do you do to improve that?

Answer

Andrew Orsich picture Andrew Orsich · Oct 5, 2011

There is now another optimization than create proper index.

db.users.ensureIndex({name:1});
db.users.find({name:"Andrei"}).count();

If you need some counters i suggest to precalculate them whenever it possible. By using atomic $inc operation and not use count({}) at all.

But mongodb guys working hard on mongodb, so, count({}) improvements they are planning in mongodb 2.1 according to jira bug.

Related questions

MySQL vs MongoDB 1000 reads

I have been very excited about MongoDb and have been testing it lately. I had a table called posts in MySQL with about 20 million records indexed only on a field called 'id'. I wanted to compare speed with MongoDB and …

Read More
When to use CouchDB over MongoDB and vice versa

I am stuck between these two NoSQL databases. In my project I will be creating a database within a database. For example, I need a solution to create dynamic tables. So users can create tables with columns and rows. I …

Read More
Fastest way to remove duplicate documents in mongodb

I have approximately 1.7M documents in mongodb (in future 10m+). Some of them represent duplicate entry which I do not want. Structure of document is something like this: { _id: 14124412, nodes: [ 12345, 54321 ], name: "Some beauty" } Document is duplicate if it has at …

Read More