public interface RelationProvider
Users may specify the fully qualified class name of a given data source. When that class is
not found Spark SQL will append the class name
DefaultSource to the path, allowing for
less verbose invocation. For example, 'org.apache.spark.sql.json' would resolve to the
data source 'org.apache.spark.sql.json.DefaultSource'
A new instance of this class with be instantiated each time a DDL call is made.