Unique, sparse index on array field - empty array behaviour different in 2.0?

[Ben Symonds]

What the subject line says really! Create a unique, sparse index on array field. Before, I could have two documents with empty array. Now, I can't.

With v1.8.1:

MongoDB shell version: 1.8.1
connecting to: odyssey_test
> use foo_test
switched to db foo_test
> db.users.ensureIndex({aliases:1},{sparse:true,unique:true})
> db.users.insert({name:"alice", aliases:[]})
> db.users.insert({name:"bob", aliases:[]})
> db.users.find()
{ "_id" : ObjectId("4e7b5b219521a5c75ce16608"), "name" : "alice", "aliases" : [ ] }
{ "_id" : ObjectId("4e7b5b289521a5c75ce16609"), "name" : "bob", "aliases" : [ ] }

with v2.0.0:

MongoDB shell version: 2.0.0
connecting to: test
> use foo_test
switched to db foo_test
> db.users.ensureIndex({aliases:1},{sparse:true,unique:true})
> db.users.insert({name:"alice", aliases:[]})
> db.users.insert({name:"bob", aliases:[]})
E11000 duplicate key error index: foo_test.users.$aliases_1 dup key: { : undefined }

If I instead create the index with v:0 (to force old-style, pre-v2.0 index type), I don't get the dup key error, i.e. same behaviour as 1.8 (as you would expect).

Is this intended behaviour? I don't see anything in release notes…

Thanks,

Ben

[Kyle Banker]

Can you create a bug report at jira.mongodb.org? This seems like a bug.

[Ben Symonds]

Sure, no problem.  Thanks for the quick response.

On 22 Sep 2011, at 17:46, Kyle Banker wrote:

Can you create a bug report at jira.mongodb.org? This seems like a bug.

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[Ben Symonds]

I opened a bug (https://jira.mongodb.org/browse/SERVER-3934) but yet to see any activity on it - is that normal?

[Kyle Banker]

Yes, this is normal. Someone will eventually assign it to a release.