Question

I have a collection called “messages”. Each message has a ‘read’ boolean value. In some instances when I retrieve the messages, I’d like to set the value to ‘true’, while returning the pre-modified value.

So, let’s say I have 1 message, whose ‘read’ value is ‘false’. When I retrieve it, I’d like to return the initial ‘false’ value, but in the same operation I’d like to set it to ‘true’.

Any way of doing that?

Answer 1

The findAndModify command is what you’re looking for:

4 . The command returns the original unmodified document selected for this update.

If you were using it in the Mongo shell, your usage would look like:

db.messages.findAndModify({query: {read: false}, update: {read: true}})

It looks like you’re using Java, though. The Java driver offers a few different signatures for findAndModify(). You can check them out in the javadoc for DBCollection.