node.js mongodb cursor looping on client request

Question

node.js mongodb cursor looping on client request

I know how to query a collection. But I have a collection with 100,000 records and I want to show only 100 items per page. The user can then select next 100 records and so on...

Since this request is coming from the user, how do I keep the cursor open on node.js for looping the next 100 items when client requests for it?

What is the standard practice?

Thanks!

node.js
mongodb

Answer 1

The standard practice for what you are referring to is something like pagination.

You don't need to keep the cursor open all the time. All you need to make sure is that you continue from the same place you left off.

The client would retain the number of records that has already been displayed and use that number inside the skip() function of the cursor.

For example:

Client is provided with 10 records. record_count = 10.
Client requests more records and includes record_count in the request.
Server uses supplied record_count in another query in the skip parameter.
Server returns another 10 records to client.
Client updates the record_count variable to now be 20.
Rinse, Repeat...

Keep in mind that you'd want your results to be sorted somehow so that your query will always return different results (the next 10 records).

I'm not too familiar with the node drivers for mongo, but in the mongo shell, you would execute the query as follows:

db.collection.find().sort( { "time": 1 } ).skip( record_count ).limit( 10 )