How can I retrieve the alias for a DataFrame in Spark

Question

I\'m using Spark 2.0.2. I have a DataFrame that has an alias on it, and I\'d like to be able to retrieve that. A simplified example of why I\'d want that is below.

Answer 1

You can try something like this but I wouldn't go so far to claim it is supported:

• Spark < 2.1:

  import org.apache.spark.sql.catalyst.plans.logical.SubqueryAlias
  import org.apache.spark.sql.Dataset
  
  def getAlias(ds: Dataset[_]) = ds.queryExecution.analyzed match {
    case SubqueryAlias(alias, _) => Some(alias)
    case _ => None
  }
  

• Spark 2.1+:

  def getAlias(ds: Dataset[_]) = ds.queryExecution.analyzed match {
    case SubqueryAlias(alias, _, _) => Some(alias)
    case _ => None
  }
  

Example usage:

val plain = Seq((1, "foo")).toDF
getAlias(plain)

Option[String] = None

val aliased = plain.alias("a dataset")
getAlias(aliased)

Option[String] = Some(a dataset)