[SPARK-31220][SQL] repartition obeys initialPartitionNum when adaptiveExecutionEnabled

sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala

@@ -2784,7 +2784,15 @@ class SQLConf extends Serializable with Logging {
 
   def cacheVectorizedReaderEnabled: Boolean = getConf(CACHE_VECTORIZED_READER_ENABLED)
 
-  def numShufflePartitions: Int = getConf(SHUFFLE_PARTITIONS)
+  def defaultNumShufflePartitions: Int = getConf(SHUFFLE_PARTITIONS)
+
+  def numShufflePartitions: Int = {
+    if (adaptiveExecutionEnabled && coalesceShufflePartitionsEnabled) {
+      getConf(COALESCE_PARTITIONS_INITIAL_PARTITION_NUM).getOrElse(defaultNumShufflePartitions)
+    } else {
+      defaultNumShufflePartitions
+    }
+  }
 
   def adaptiveExecutionEnabled: Boolean = getConf(ADAPTIVE_EXECUTION_ENABLED)
 
@@ -2797,9 +2805,6 @@ class SQLConf extends Serializable with Logging {
 
   def coalesceShufflePartitionsEnabled: Boolean = getConf(COALESCE_PARTITIONS_ENABLED)
 
-  def initialShufflePartitionNum: Int =
-    getConf(COALESCE_PARTITIONS_INITIAL_PARTITION_NUM).getOrElse(numShufflePartitions)
-
   def minBatchesToRetain: Int = getConf(MIN_BATCHES_TO_RETAIN)
 
   def maxBatchesToRetainInMemory: Int = getConf(MAX_BATCHES_TO_RETAIN_IN_MEMORY)

sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/EnsureRequirements.scala

@@ -35,12 +35,6 @@ import org.apache.spark.sql.internal.SQLConf
  * the input partition ordering requirements are met.
  */
 case class EnsureRequirements(conf: SQLConf) extends Rule[SparkPlan] {
-  private def defaultNumPreShufflePartitions: Int =
-    if (conf.adaptiveExecutionEnabled && conf.coalesceShufflePartitionsEnabled) {
-      conf.initialShufflePartitionNum
-    } else {
-      conf.numShufflePartitions
-    }
 
   private def ensureDistributionAndOrdering(operator: SparkPlan): SparkPlan = {
     val requiredChildDistributions: Seq[Distribution] = operator.requiredChildDistribution
@@ -57,7 +51,7 @@ case class EnsureRequirements(conf: SQLConf) extends Rule[SparkPlan] {
         BroadcastExchangeExec(mode, child)
       case (child, distribution) =>
         val numPartitions = distribution.requiredNumPartitions
-          .getOrElse(defaultNumPreShufflePartitions)
+          .getOrElse(conf.numShufflePartitions)
         ShuffleExchangeExec(distribution.createPartitioning(numPartitions), child)
     }
 
@@ -95,7 +89,7 @@ case class EnsureRequirements(conf: SQLConf) extends Rule[SparkPlan] {
         // expected number of shuffle partitions. However, if it's smaller than
         // `conf.numShufflePartitions`, we pick `conf.numShufflePartitions` as the
         // expected number of shuffle partitions.
-        math.max(nonShuffleChildrenNumPartitions.max, conf.numShufflePartitions)
+        math.max(nonShuffleChildrenNumPartitions.max, conf.defaultNumShufflePartitions)
       } else {
         childrenNumPartitions.max
       }

sql/core/src/test/scala/org/apache/spark/sql/execution/adaptive/AdaptiveQueryExecSuite.scala

@@ -1021,4 +1021,20 @@ class AdaptiveQueryExecSuite
       }
     }
   }
+
+  test("SPARK-31220 repartition obeys initialPartitionNum when adaptiveExecutionEnabled") {
+    Seq(true, false).foreach { adaptiveExecutionEnabled =>
+      withSQLConf(
+        SQLConf.ADAPTIVE_EXECUTION_ENABLED.key -> s"$adaptiveExecutionEnabled",
+        SQLConf.SHUFFLE_PARTITIONS.key -> "6",
+        SQLConf.COALESCE_PARTITIONS_INITIAL_PARTITION_NUM.key -> "7") {
+        val partitionsNum = spark.range(10).repartition($"id").rdd.collectPartitions().length
+        if (adaptiveExecutionEnabled) {
+          assert(partitionsNum === 7)
+        } else {
+          assert(partitionsNum === 6)
+        }
+      }
+    }
+  }
 }