case class HadoopFsRelation(
location: FileIndex,
partitionSchema: StructType,
dataSchema: StructType,
bucketSpec: Option[BucketSpec],
fileFormat: FileFormat,
options: Map[String, String])(val sparkSession: SparkSession)
extends BaseRelation with FileRelationHadoopFsRelation
HadoopFsRelation is a BaseRelation in a SparkSession (through which it gets to the current SQLContext).
HadoopFsRelation requires a schema (as StructType) that it expands with the input partitionSchema schema.
sizeInBytes and inputFiles (from the base BaseRelation) use the input FileIndex to compute the size and input files, respectively.