update

Author: allisonwang-db

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala

@@ -1033,7 +1033,7 @@ object CombineFilters extends Rule[LogicalPlan] with PredicateHelper {
 object EliminateSorts extends Rule[LogicalPlan] {
   def apply(plan: LogicalPlan): LogicalPlan = plan transform applyLocally
 
-  val applyLocally: PartialFunction[LogicalPlan, LogicalPlan] = {
+  private val applyLocally: PartialFunction[LogicalPlan, LogicalPlan] = {
     case s @ Sort(orders, _, child) if orders.isEmpty || orders.exists(_.child.foldable) =>
       val newOrders = orders.filterNot(_.child.foldable)
       if (newOrders.isEmpty) {

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

@@ -23,7 +23,10 @@ import org.apache.spark.sql.internal.SQLConf
 
 /**
  * Remove redundant SortExec node from the spark plan. A sort node is redundant when
- * its child satisfies both its sort orders and its required child distribution.
+ * its child satisfies both its sort orders and its required child distribution. Note
+ * this rule differs from the Optimizer rule EliminateSorts in that this rule also checks
+ * if the child satisfies the required distribution so that it is safe to remove not only a
+ * local sort but also a global sort when its child already satisfies required sort orders.
  */
 object RemoveRedundantSorts extends Rule[SparkPlan] {
   def apply(plan: SparkPlan): SparkPlan = {

sql/core/src/test/scala/org/apache/spark/sql/execution/RemoveRedundantSortsSuite.scala

@@ -64,7 +64,7 @@ abstract class RemoveRedundantSortsSuiteBase
     withTempView("t1", "t2") {
       spark.range(1000).select('id as "key").createOrReplaceTempView("t1")
       spark.range(1000).select('id as "key").createOrReplaceTempView("t2")
-      
+
       val queryTemplate = """
         |SELECT /*+ BROADCAST(%s) */ t1.key FROM
         | (SELECT key FROM t1 WHERE key > 10 ORDER BY key DESC LIMIT 10) t1
@@ -74,17 +74,25 @@ abstract class RemoveRedundantSortsSuiteBase
         |ORDER BY %s
       """.stripMargin
 
-      val innerJoinAsc = queryTemplate.format("t1", "t2.key ASC")
-      checkSorts(innerJoinAsc, 1, 1)
-
-      val innerJoinDesc = queryTemplate.format("t1", "t2.key DESC")
-      checkSorts(innerJoinDesc, 0, 1)
-
-      val innerJoinDesc1 = queryTemplate.format("t1", "t1.key DESC")
-      checkSorts(innerJoinDesc1, 1, 1)
-
-      val leftOuterJoinDesc = queryTemplate.format("t2", "t1.key DESC")
-      checkSorts(leftOuterJoinDesc, 0, 1)
+      // No sort should be removed since the stream side (t2) order DESC
+      // does not satisfy the required sort order ASC.
+      val buildLeftOrderByRightAsc = queryTemplate.format("t1", "t2.key ASC")
+      checkSorts(buildLeftOrderByRightAsc, 1, 1)
+
+      // The top sort node should be removed since the stream side (t2) order DESC already
+      // satisfies the required sort order DESC.
+      val buildLeftOrderByRightDesc = queryTemplate.format("t1", "t2.key DESC")
+      checkSorts(buildLeftOrderByRightDesc, 0, 1)
+
+      // No sort should be removed since the sort ordering from broadcast-hash join is based
+      // on the stream side (t2) and the required sort order is from t1.
+      val buildLeftOrderByLeftDesc = queryTemplate.format("t1", "t1.key DESC")
+      checkSorts(buildLeftOrderByLeftDesc, 1, 1)
+
+      // The top sort node should be removed since the stream side (t1) order DESC already
+      // satisfies the required sort order DESC.
+      val buildRightOrderByLeftDesc = queryTemplate.format("t2", "t1.key DESC")
+      checkSorts(buildRightOrderByLeftDesc, 0, 1)
     }
   }
 
@@ -104,7 +112,8 @@ abstract class RemoveRedundantSortsSuiteBase
       val queryAsc = query + " ASC"
       checkSorts(queryAsc, 2, 3)
 
-      // Top level sort should only be eliminated if it's order is descending with SMJ.
+      // The top level sort should not be removed since the child output ordering is ASC and
+      // the required ordering is DESC.
       val queryDesc = query + " DESC"
       checkSorts(queryDesc, 3, 3)
     }