Merge pull request apache#56 from liancheng/unapplySeqForRow

Added Row.unapplySeq to extract fields from a Row object.

Author: marmbrus

sql/catalyst/src/main/scala/org/apache/spark/sql/package.scala

@@ -31,4 +31,19 @@ package object sql {
   protected[sql] type Logging = com.typesafe.scalalogging.slf4j.Logging
 
   type Row = catalyst.expressions.Row
+
+  object Row {
+    /**
+     * This method can be used to extract fields from a [[Row]] object in a pattern match. Example:
+     * {{{
+     * import org.apache.spark.sql._
+     *
+     * val pairs = sql("SELECT key, value FROM src").rdd.map {
+     *   case Row(key: Int, value: String) =>
+     *     key -> value
+     * }
+     * }}}
+     */
+    def unapplySeq(row: Row): Some[Seq[Any]] = Some(row)
+  }
 }