[SPARK-10321] sizeInBytes in HadoopFsRelation

Having sizeInBytes in HadoopFsRelation to enable broadcast join.

cc marmbrus

Author: Davies Liu <davies@databricks.com>

Closes #8490 from davies/sizeInByte.

sql/core/src/main/scala/org/apache/spark/sql/sources/interfaces.scala

@@ -518,6 +518,8 @@ abstract class HadoopFsRelation private[sql](maybePartitionSpec: Option[Partitio
 
   override def inputFiles: Array[String] = cachedLeafStatuses().map(_.getPath.toString).toArray
 
+  override def sizeInBytes: Long = cachedLeafStatuses().map(_.getLen).sum
+
   /**
    * Partition columns.  Can be either defined by [[userDefinedPartitionColumns]] or automatically
    * discovered.  Note that they should always be nullable.