[SPARK-3058] [SQL] Support EXTENDED for EXPLAIN

Provide `extended` keyword support for `explain` command in SQL. e.g.
```
explain extended select key as a1, value as a2 from src where key=1;
== Parsed Logical Plan ==
Project ['key AS a1#3,'value AS a2#4]
 Filter ('key = 1)
  UnresolvedRelation None, src, None

== Analyzed Logical Plan ==
Project [key#8 AS a1#3,value#9 AS a2#4]
 Filter (CAST(key#8, DoubleType) = CAST(1, DoubleType))
  MetastoreRelation default, src, None

== Optimized Logical Plan ==
Project [key#8 AS a1#3,value#9 AS a2#4]
 Filter (CAST(key#8, DoubleType) = 1.0)
  MetastoreRelation default, src, None

== Physical Plan ==
Project [key#8 AS a1#3,value#9 AS a2#4]
 Filter (CAST(key#8, DoubleType) = 1.0)
  HiveTableScan [key#8,value#9], (MetastoreRelation default, src, None), None

Code Generation: false
== RDD ==
(2) MappedRDD[14] at map at HiveContext.scala:350
  MapPartitionsRDD[13] at mapPartitions at basicOperators.scala:42
  MapPartitionsRDD[12] at mapPartitions at basicOperators.scala:57
  MapPartitionsRDD[11] at mapPartitions at TableReader.scala:112
  MappedRDD[10] at map at TableReader.scala:240
  HadoopRDD[9] at HadoopRDD at TableReader.scala:230
```

It's the sub task of #1847. But can go without any dependency.

Author: Cheng Hao <hao.cheng@intel.com>

Closes #1962 from chenghao-intel/explain_extended and squashes the following commits:

295db74 [Cheng Hao] Fix bug in printing the simple execution plan
48bc989 [Cheng Hao] Support EXTENDED for EXPLAIN

(cherry picked from commit 156eb3966176de02ec3ec90ae10e50a7ebfbbf4f)
Signed-off-by: Michael Armbrust <michael@databricks.com>

3 files changed, 19 insertions, 8 deletions

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala b/sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala
index af9f7c62a1..8a9f4deb6a 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala
@@ -408,10 +408,18 @@ class SQLContext(@transient val sparkContext: SparkContext)
     protected def stringOrError[A](f: => A): String =
       try f.toString catch { case e: Throwable => e.toString }
 
-    def simpleString: String = stringOrError(executedPlan)
+    def simpleString: String = 
+      s"""== Physical Plan ==
+         |${stringOrError(executedPlan)}
+      """
 
     override def toString: String =
-      s"""== Logical Plan ==
+      // TODO previously will output RDD details by run (${stringOrError(toRdd.toDebugString)})
+      // however, the `toRdd` will cause the real execution, which is not what we want.
+      // We need to think about how to avoid the side effect.
+      s"""== Parsed Logical Plan ==
+         |${stringOrError(logical)}
+         |== Analyzed Logical Plan ==
          |${stringOrError(analyzed)}
          |== Optimized Logical Plan ==
          |${stringOrError(optimizedPlan)}
@@ -419,7 +427,6 @@ class SQLContext(@transient val sparkContext: SparkContext)
          |${stringOrError(executedPlan)}
          |Code Generation: ${executedPlan.codegenEnabled}
          |== RDD ==
-         |${stringOrError(toRdd.toDebugString)}
       """.stripMargin.trim
   }
 
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala
index 517b77804a..8dacb84c8a 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala
@@ -301,8 +301,8 @@ private[sql] abstract class SparkStrategies extends QueryPlanner[SparkPlan] {
     def apply(plan: LogicalPlan): Seq[SparkPlan] = plan match {
       case logical.SetCommand(key, value) =>
         Seq(execution.SetCommand(key, value, plan.output)(context))
-      case logical.ExplainCommand(logicalPlan) =>
-        Seq(execution.ExplainCommand(logicalPlan, plan.output)(context))
+      case logical.ExplainCommand(logicalPlan, extended) =>
+        Seq(execution.ExplainCommand(logicalPlan, plan.output, extended)(context))
       case logical.CacheCommand(tableName, cache) =>
         Seq(execution.CacheCommand(tableName, cache)(context))
       case _ => Nil
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/commands.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/commands.scala
index 38f37564f1..031b695169 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/commands.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/commands.scala
@@ -108,15 +108,19 @@ case class SetCommand(
  */
 @DeveloperApi
 case class ExplainCommand(
-    logicalPlan: LogicalPlan, output: Seq[Attribute])(
+    logicalPlan: LogicalPlan, output: Seq[Attribute], extended: Boolean)(
     @transient context: SQLContext)
   extends LeafNode with Command {
 
   // Run through the optimizer to generate the physical plan.
   override protected[sql] lazy val sideEffectResult: Seq[String] = try {
-    "Physical execution plan:" +: context.executePlan(logicalPlan).executedPlan.toString.split("\n")
+    // TODO in Hive, the "extended" ExplainCommand prints the AST as well, and detailed properties.
+    val queryExecution = context.executePlan(logicalPlan)
+    val outputString = if (extended) queryExecution.toString else queryExecution.simpleString
+
+    outputString.split("\n")
   } catch { case cause: TreeNodeException[_] =>
-    "Error occurred during query planning: " +: cause.getMessage.split("\n")
+    ("Error occurred during query planning: \n" + cause.getMessage).split("\n")
   }
 
   def execute(): RDD[Row] = {