[SPARK-3349][SQL] Output partitioning of limit should not be inherite…

…d from child

This resolves https://issues.apache.org/jira/browse/SPARK-3349

Author: Eric Liang <ekl@google.com>

Closes #2262 from ericl/spark-3349 and squashes the following commits:

3e1b05c [Eric Liang] add regression test
ac32723 [Eric Liang] make limit/takeOrdered output SinglePartition

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

@@ -27,7 +27,7 @@ import org.apache.spark.shuffle.sort.SortShuffleManager
 import org.apache.spark.sql.catalyst.ScalaReflection
 import org.apache.spark.sql.catalyst.errors._
 import org.apache.spark.sql.catalyst.expressions._
-import org.apache.spark.sql.catalyst.plans.physical.{ClusteredDistribution, OrderedDistribution, UnspecifiedDistribution}
+import org.apache.spark.sql.catalyst.plans.physical.{ClusteredDistribution, OrderedDistribution, SinglePartition, UnspecifiedDistribution}
 import org.apache.spark.util.MutablePair
 
 /**
@@ -100,6 +100,7 @@ case class Limit(limit: Int, child: SparkPlan)
   private def sortBasedShuffleOn = SparkEnv.get.shuffleManager.isInstanceOf[SortShuffleManager]
 
   override def output = child.output
+  override def outputPartitioning = SinglePartition
 
   /**
    * A custom implementation modeled after the take function on RDDs but which never runs any job
@@ -173,6 +174,7 @@ case class Limit(limit: Int, child: SparkPlan)
 case class TakeOrdered(limit: Int, sortOrder: Seq[SortOrder], child: SparkPlan) extends UnaryNode {
 
   override def output = child.output
+  override def outputPartitioning = SinglePartition
 
   val ordering = new RowOrdering(sortOrder, child.output)
 

sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala

@@ -359,6 +359,23 @@ class SQLQuerySuite extends QueryTest with BeforeAndAfterAll {
       (null, null, 6, "F") :: Nil)
   }
 
+  test("SPARK-3349 partitioning after limit") {
+    sql("SELECT DISTINCT n FROM lowerCaseData ORDER BY n DESC")
+      .limit(2)
+      .registerTempTable("subset1")
+    sql("SELECT DISTINCT n FROM lowerCaseData")
+      .limit(2)
+      .registerTempTable("subset2")
+    checkAnswer(
+      sql("SELECT * FROM lowerCaseData INNER JOIN subset1 ON subset1.n = lowerCaseData.n"),
+      (3, "c", 3) ::
+      (4, "d", 4) :: Nil)
+    checkAnswer(
+      sql("SELECT * FROM lowerCaseData INNER JOIN subset2 ON subset2.n = lowerCaseData.n"),
+      (1, "a", 1) ::
+      (2, "b", 2) :: Nil)
+  }
+
   test("mixed-case keywords") {
     checkAnswer(
       sql(