Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/2475#discussion_r18122137
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/commands.scala ---
@@ -44,6 +46,34 @@ trait Command {
override def execute(): RDD[Row] =
sqlContext.sparkContext.parallelize(sideEffectResult, 1)
}
+trait RunnableCommand extends logical.Command {
+ self: Product =>
+
+ def output: Seq[Attribute]
+ def run(sqlContext: SQLContext): Seq[Row]
+}
+
+case class ExecutedCommand(cmd: RunnableCommand) extends SparkPlan {
+ /**
+ * A concrete command should override this lazy field to wrap up any
side effects caused by the
+ * command or any other computation that should be evaluated exactly
once. The value of this field
+ * can be used as the contents of the corresponding RDD generated from
the physical plan of this
+ * command.
+ *
+ * The `execute()` method of all the physical command classes should
reference `sideEffectResult`
+ * so that the command can be executed eagerly right after the command
query is created.
+ */
+ protected[sql] lazy val sideEffectResult: Seq[Row] = cmd.run(sqlContext)
+
+ override def output = cmd.output
+
+ def children = Nil
--- End diff --
override?
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