How to create unique index through create index.

[Raman Goyal]

I am trying to create a unique index via create index method. But following command is not providing a unique index.

collQueries.createIndex(Document("name" -> 1, "unique" -> true))

And neither this command.

collQueries.createIndex(Document("name" -> 1, "unique" -> true), IndexOptions()) 

 Can anyone please help on how to create unique index using Mongo-Scala Driver.

[Asya Kamsky]

Create index takes two arguments. The first specifies the index, the second specifies options.

I'm guessing you want something like:

collection.createIndex(Document("name" -> 1), Document("unique" -> false))

If that's not in the ballpark, you'll have to look at the docs for exact syntax you need:

https://mongodb.github.io/mongo-scala-driver/1.1/builders/indexes/

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[Raman Goyal]

I looked into it and finally figure out that this is the way to create unique index.

collQueries.createIndex(Document("name" -> 1), IndexOptions().unique(true))

But to my surprise this is not creating any unique index in the database. Can you please look into that?

[Wan Bachtiar]

Hi Raman,

The MongoDB Scala Driver uses the Observable model. All Observables returned from the API are cold, meaning that no I/O happens until they are subscribe to.

For example, you can use toFuture():scala.concurrent.Future[Seq[T]]) which automatically subscribes to the Observable and uses the collect:org.mongodb.scala.Observable[Seq[T]]) method to aggregate the results.

collection.createIndex(Document("user" -> 1), IndexOptions().unique(true)).toFuture()

Also have a look at some helper methods defined in Helpers.scala to get and print results. For example, using the results() blocks until the Observable is completed and returns the collected results

// Returns: { "v" : 1, "unique" : true, "key" : { "name" : 1 }, "name" : "name_1", "ns" : "mydb.test" }
collection.createIndex(Document("name" -> 1), IndexOptions().unique(true)).results()

Check out the Quick Tour Primer for more information on the Observable API.

Regards,

Wan.

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