Case insensitive sorting in MongoDB

Update: As of now mongodb have case insensitive indexes:

Users.find({})
  .collation({locale: "en" })
  .sort({name: 1})
  .exec()
  .then(...)

shell:

db.getCollection('users')
  .find({})
  .collation({'locale':'en'})
  .sort({'firstName':1})

Update: This answer is out of date, 3.4 will have case insensitive indexes. Look to the JIRA for more information https://jira.mongodb.org/browse/SERVER-90

Unfortunately MongoDB does not yet have case insensitive indexes: https://jira.mongodb.org/browse/SERVER-90 and the task has been pushed back.

This means the only way to sort case insensitive currently is to actually create a specific "lower cased" field, copying the value (lower cased of course) of the sort field in question and sorting on that instead.

Sorting does work like that in MongoDB but you can do this on the fly with aggregate:

Take the following data:

{ "field" : "BBB" }
{ "field" : "aaa" }
{ "field" : "AAA" }

So with the following statement:

db.collection.aggregate([
    { "$project": {
       "field": 1,
       "insensitive": { "$toLower": "$field" }
    }},
    { "$sort": { "insensitive": 1 } }
])

Would produce results like:

{
    "field" : "aaa",
    "insensitive" : "aaa"
},
{
    "field" : "AAA",
    "insensitive" : "aaa"
},
{
    "field" : "BBB",
    "insensitive" : "bbb"
}

The actual order of insertion would be maintained for any values resulting in the same key when converted.

This has been an issue for quite a long time on MongoDB JIRA, but it is solved now. Take a look at this release notes for detailed documentation. You should use collation.

User.find()
    .collation({locale: "en" }) //or whatever collation you want
    .sort({name:1})
    .exec(function(err, users) {
        // use your case insensitive sorted results
    });

Adding the code .collation({'locale':'en'}) helped to solve my issue.

As of now (mongodb 4), you can do the following:

mongo shell:

db.getCollection('users')
  .find({})
  .collation({'locale':'en'})
  .sort({'firstName':1});

mongoose:

Users.find({})
  .collation({locale: "en" })
  .sort({name: 1})
  .exec()
  .then(...)

Here are supported languages and locales by mongodb.