How to do pagination using range queries in MongoDB?

Question

I\'m probably missing something since I\'m still learning the ins and outs of MongoDB, but I need help with paging a collection.

I have a collection that has a lis

Answer 1

You just need to call skip on the cursor

see MongoDB documentation on cursor skip "This approach may be useful in implementing “paged” results".

This example is taken from Mongodb's example

function printStudents(pageNumber, nPerPage) {
   print("Page: " + pageNumber);
   db.students.find().skip((pageNumber-1)*nPerPage).limit(nPerPage).forEach( function(student) { print(student.name + "<p>"); } );
}

Answer 2

Since the collection I was paging had duplicate values I had to create a compound index on ProductName and id.

Create Compound Index

db.ProductGuideItem.ensureIndex({ ProductName:1, _id:1});

This solved my problem.
Reference: https://groups.google.com/d/msg/mongodb-user/3EZZIRJzW_A/oYH79npKZHkJ

Assuming you have these values:

{a:1, b:1}
{a:2, b:1}
{a:2, b:2}
{a:2, b:3}
{a:3, b:1}

So you do this for the range based pagination (page size of 2):

1st Page

find().sort({a:1, b:1}).limit(2)
{a:1, b:1}
{a:2, b:1}

2nd Page

find().min({a:2, b:1}).sort({a:1, b:1}).skip(1).limit(2)

{a:2, b:2}
{a:2, b:3}

3rd Page

find().min({a:2, b:3}).sort({a:1, b:1}).skip(1).limit(2)
{a:3, b:1}

Here are the docs for $min/max: http://www.mongodb.org/display/DOCS/min+and+max+Query+Specifiers

If you don't have duplicate values in your collection, you don't need to use min & max or create a compound index. You can just use $lt & $gt.