fix explain

Author: lianhuiwang

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala

@@ -263,7 +263,9 @@ abstract class QueryPlan[PlanType <: QueryPlan[PlanType]] extends TreeNode[PlanT
    * All the subqueries of current plan.
    */
   def subqueries: Seq[PlanType] = {
-    expressions.flatMap(_.collect {case e: SubqueryExpression => e.plan.asInstanceOf[PlanType]})
+    expressions.flatMap(_.collect {
+      case e: SubqueryExpression => e
+    }).distinct.map(_.plan.asInstanceOf[PlanType])
   }
 
   override protected def innerChildren: Seq[QueryPlan[_]] = subqueries

sql/core/src/main/scala/org/apache/spark/sql/execution/subquery.scala

@@ -94,7 +94,7 @@ case class ReusedScalarSubquery(
     child: ScalarSubquery) extends UnaryExpression {
 
   override def dataType: DataType = child.dataType
-  override def toString: String = s"ReusedSubquery#${exprId.id} ($child)"
+  override def toString: String = s"ReusedSubquery#${exprId.id}($child)"
 
   override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode =
     defineCodeGen(ctx, ev, c => c)