Moved logical command classes to a separate file

Author: liancheng

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala

@@ -20,7 +20,7 @@ package org.apache.spark.sql.catalyst.plans.logical
 import org.apache.spark.sql.catalyst.errors.TreeNodeException
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.QueryPlan
-import org.apache.spark.sql.catalyst.types.{StringType, StructType}
+import org.apache.spark.sql.catalyst.types.StructType
 import org.apache.spark.sql.catalyst.trees
 
 abstract class LogicalPlan extends QueryPlan[LogicalPlan] {
@@ -96,44 +96,6 @@ abstract class LeafNode extends LogicalPlan with trees.LeafNode[LogicalPlan] {
   def references = Set.empty
 }
 
-/**
- * A logical node that represents a non-query command to be executed by the system.  For example,
- * commands can be used by parsers to represent DDL operations.
- */
-abstract class Command extends LeafNode {
-  self: Product =>
-  def output: Seq[Attribute] = Seq.empty  // TODO: SPARK-2081 should fix this
-}
-
-/**
- * Returned for commands supported by a given parser, but not catalyst.  In general these are DDL
- * commands that are passed directly to another system.
- */
-case class NativeCommand(cmd: String) extends Command
-
-/**
- * Commands of the form "SET (key) (= value)".
- */
-case class SetCommand(key: Option[String], value: Option[String]) extends Command {
-  override def output = Seq(
-    AttributeReference("key", StringType, nullable = false)(),
-    AttributeReference("value", StringType, nullable = false)()
-  )
-}
-
-/**
- * Returned by a parser when the users only wants to see what query plan would be executed, without
- * actually performing the execution.
- */
-case class ExplainCommand(plan: LogicalPlan) extends Command {
-  override def output = Seq(AttributeReference("plan", StringType, nullable = false)())
-}
-
-/**
- * Returned for the "CACHE TABLE tableName" and "UNCACHE TABLE tableName" command.
- */
-case class CacheCommand(tableName: String, doCache: Boolean) extends Command
-
 /**
  * A logical plan node with single child.
  */

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/commands.scala

@@ -0,0 +1,60 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.catalyst.plans.logical
+
+import org.apache.spark.sql.catalyst.expressions.{AttributeReference, Attribute}
+import org.apache.spark.sql.catalyst.types.StringType
+
+/**
+ * A logical node that represents a non-query command to be executed by the system.  For example,
+ * commands can be used by parsers to represent DDL operations.
+ */
+abstract class Command extends LeafNode {
+  self: Product =>
+  def output: Seq[Attribute] = Seq.empty  // TODO: SPARK-2081 should fix this
+}
+
+/**
+ * Returned for commands supported by a given parser, but not catalyst.  In general these are DDL
+ * commands that are passed directly to another system.
+ */
+case class NativeCommand(cmd: String) extends Command
+
+/**
+ * Commands of the form "SET (key) (= value)".
+ */
+case class SetCommand(key: Option[String], value: Option[String]) extends Command {
+  override def output = Seq(
+    AttributeReference("key", StringType, nullable = false)(),
+    AttributeReference("value", StringType, nullable = false)()
+  )
+}
+
+/**
+ * Returned by a parser when the users only wants to see what query plan would be executed, without
+ * actually performing the execution.
+ */
+case class ExplainCommand(plan: LogicalPlan) extends Command {
+  override def output = Seq(AttributeReference("plan", StringType, nullable = false)())
+}
+
+/**
+ * Returned for the "CACHE TABLE tableName" and "UNCACHE TABLE tableName" command.
+ */
+case class CacheCommand(tableName: String, doCache: Boolean) extends Command
+