I was able to use a workaround, you can "normalize" the data

$db.bar.find()
{_id: 10, foo: 1, b:1}
{_id: 11, foo: 1, b:2}
{_id: 12, foo: 1, b:3}

$db.foo.find()
{_id: 1, bar:[10,11,12]}

Then you can

• use $addToSet on foo.bar to manage unique items
• add compound key bar {foo,b}

  to restrict duplicates

• use upsert on bar collection to easily add new items or update existing ones. trick is to read the return from the upsert use that in the $addToSet operation on foo

Any movement on this?

Is there any update for this bug?

Again, any movement on this? I will have to re-architect my solution to go across multiple collections (which would then argue why use mongo) rather than have the ability for intra-document uniqueness.

i just came up against this, and it is resulting in a non-trivial amount of effort to enforce this at the application level. gotta say, the fact that there are almost 60 votes for this issue, half a dozen stack overflow type posts, and it has been sitting here for 7 years after Eliot stated "its mostly clear its a bug", kind of makes me sad.