Left outer join

[Thomas FOURNIER]

Hello, I'm facing an issue with leftOuterJoin:

- input is a DataSet[String]
- metrics is a DataSet[(String,Long)]

I'm doing a leftOuterJoin like this:

input
.leftOuterJoin(metrics)
.where(0)
.equalTo(0) {
     (left,right)  =>     ...
}


But I encounter the following error:
Specifying keys via field positions is only valid for tuple data types.
Type: String

What is the correct way to handle this case (where left member has only one
field ?)

Thanks
Regards

Thomas