MongoDB: Is it possible to make a case-insensitive query?

Question

Example:

> db.stuff.save({"foo":"bar"});  > db.stuff.find({"foo":"bar"}).count(); 1 > db.stuff.find({"foo":"BAR"}).count(); 0 

Answer 1

You could use a regex.

In your example that would be:

db.stuff.find( { foo: /^bar$/i } ); 

I must say, though, maybe you could just downcase (or upcase) the value on the way in rather than incurring the extra cost every time you find it. Obviously this wont work for people's names and such, but maybe use-cases like tags.

Answer 2

UPDATE:

The original answer is now obsolete. Mongodb now supports advanced full text searching, with many features.

ORIGINAL ANSWER:

It should be noted that searching with regex's case insensitive /i means that mongodb cannot search by index, so queries against large datasets can take a long time.

Even with small datasets, it's not very efficient. You take a far bigger cpu hit than your query warrants, which could become an issue if you are trying to achieve scale.

As an alternative, you can store an uppercase copy and search against that. For instance, I have a User table that has a username which is mixed case, but the id is an uppercase copy of the username. This ensures case-sensitive duplication is impossible (having both "Foo" and "foo" will not be allowed), and I can search by id = username.toUpperCase() to get a case-insensitive search for username.

If your field is large, such as a message body, duplicating data is probably not a good option. I believe using an extraneous indexer like Apache Lucene is the best option in that case.