MongoDB array index

Question

I want to create a simple filesystem implementation with mongodb.

Consider the schema,

FSSchema = new mongoose.Schema({
    fname : String,
    path : [String],
    content : Schema.Types.Mixed,
    user : {
       type : Schema.ObjectId,
       ref : 'User'
    }
})    
// Create compount index
FSSchema.index({ path : 1 , fname : 1 } , { unique : true })
mongoose.model('Data', DataSchema)

However my unit tests fail when creating two distinct entries

user1 = new Data({ fname : 'name'}, path: ['fld1','fld2']})
user1 = new Data({ fname : 'name'}, path: ['fld1','fld3']})

which respectively should refer to 'fld1/fld2/name' and 'fld1/fld3/name'. The failure is because apparently only 'name' and 'fld1' get used in the index.

How would I go about creating such a compound index?

Note: I know the obvious solution is to have path as a single string with a file separator such as '/'. Just wondering if using string arrays in indices is possible.

I actually have more fields in the schema, namely a user field (I will edit the question to reflect this). I want to get all data object for a particular user and then use the path to build a tree on the client side. So my query would be something like Data.find({ user : user._id }) — Joe
– Joe, Commented Nov 24, 2013 at 14:21
it looks like you can't do it in the database. Check out the answers to this question: stackoverflow.com/questions/4435637 . — idbentley
– idbentley, Commented Nov 24, 2013 at 14:41
You can't do it because an array is meant to list an number of equivalent values and you have it as related values. That's fine, and it flattens the hierarchy for indexing/searching, but you don't want to enforce uniqueness this way. — Asya Kamsky
– Asya Kamsky, Commented Nov 24, 2013 at 20:01

WiredPrairie · Accepted Answer · 2013-11-24 16:18:27Z

2

You'll need to combine the path into a single value. It's an intentional feature of MongoDb that each element of any array is indexed, so you're seeing the duplicate error when trying to insert the same two values. If having the path as distinct directories is important, you may want to double store the data, once as a full path for uniqueness, and a second as you have it. Don't enforce uniqueness though on the array as you had done.

answered Nov 24, 2013 at 16:18

WiredPrairie

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1 Comment

AJcodez Over a year ago

Thanks, couldn't find anything confirming unique array indexes for every element.

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