[SPARK-20920][SQL] ForkJoinPool pools are leaked when writing hive tables with many partitions

## What changes were proposed in this pull request?

Don't leave thread pool running from AlterTableRecoverPartitionsCommand DDL command

## How was this patch tested?

Existing tests.

Author: Sean Owen <sowen@cloudera.com>

Closes apache#18216 from srowen/SPARK-20920.

Author: srowen

sql/core/src/main/scala/org/apache/spark/sql/execution/command/ddl.scala

@@ -21,7 +21,6 @@ import java.util.Locale
 
 import scala.collection.{GenMap, GenSeq}
 import scala.collection.parallel.ForkJoinTaskSupport
-import scala.concurrent.forkjoin.ForkJoinPool
 import scala.util.control.NonFatal
 
 import org.apache.hadoop.conf.Configuration
@@ -36,7 +35,7 @@ import org.apache.spark.sql.catalyst.catalog.CatalogTypes.TablePartitionSpec
 import org.apache.spark.sql.catalyst.expressions.{Attribute, AttributeReference}
 import org.apache.spark.sql.execution.datasources.PartitioningUtils
 import org.apache.spark.sql.types._
-import org.apache.spark.util.SerializableConfiguration
+import org.apache.spark.util.{SerializableConfiguration, ThreadUtils}
 
 // Note: The definition of these commands are based on the ones described in
 // https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL
@@ -588,8 +587,15 @@ case class AlterTableRecoverPartitionsCommand(
     val threshold = spark.conf.get("spark.rdd.parallelListingThreshold", "10").toInt
     val hadoopConf = spark.sparkContext.hadoopConfiguration
     val pathFilter = getPathFilter(hadoopConf)
-    val partitionSpecsAndLocs = scanPartitions(spark, fs, pathFilter, root, Map(),
-      table.partitionColumnNames, threshold, spark.sessionState.conf.resolver)
+
+    val evalPool = ThreadUtils.newForkJoinPool("AlterTableRecoverPartitionsCommand", 8)
+    val partitionSpecsAndLocs: Seq[(TablePartitionSpec, Path)] =
+      try {
+        scanPartitions(spark, fs, pathFilter, root, Map(), table.partitionColumnNames, threshold,
+          spark.sessionState.conf.resolver, new ForkJoinTaskSupport(evalPool)).seq
+      } finally {
+        evalPool.shutdown()
+      }
     val total = partitionSpecsAndLocs.length
     logInfo(s"Found $total partitions in $root")
 
@@ -610,8 +616,6 @@ case class AlterTableRecoverPartitionsCommand(
     Seq.empty[Row]
   }
 
-  @transient private lazy val evalTaskSupport = new ForkJoinTaskSupport(new ForkJoinPool(8))
-
   private def scanPartitions(
       spark: SparkSession,
       fs: FileSystem,
@@ -620,7 +624,8 @@ case class AlterTableRecoverPartitionsCommand(
       spec: TablePartitionSpec,
       partitionNames: Seq[String],
       threshold: Int,
-      resolver: Resolver): GenSeq[(TablePartitionSpec, Path)] = {
+      resolver: Resolver,
+      evalTaskSupport: ForkJoinTaskSupport): GenSeq[(TablePartitionSpec, Path)] = {
     if (partitionNames.isEmpty) {
       return Seq(spec -> path)
     }
@@ -644,7 +649,7 @@ case class AlterTableRecoverPartitionsCommand(
         val value = ExternalCatalogUtils.unescapePathName(ps(1))
         if (resolver(columnName, partitionNames.head)) {
           scanPartitions(spark, fs, filter, st.getPath, spec ++ Map(partitionNames.head -> value),
-            partitionNames.drop(1), threshold, resolver)
+            partitionNames.drop(1), threshold, resolver, evalTaskSupport)
         } else {
           logWarning(
             s"expected partition column ${partitionNames.head}, but got ${ps(0)}, ignoring it")