Github user chenghao-intel commented on a diff in the pull request:
https://github.com/apache/spark/pull/9483#discussion_r53124605
--- Diff:
sql/hive/src/main/scala/org/apache/spark/sql/hive/ParallelUnionRDD.scala ---
@@ -0,0 +1,52 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.hive
+
+import java.util.concurrent.Callable
+
+import org.apache.spark.rdd.{RDD, UnionPartition, UnionRDD}
+import org.apache.spark.util.ThreadUtils
+import org.apache.spark.{Partition, SparkContext}
+
+import scala.reflect.ClassTag
+
+class ParallelUnionRDD[T: ClassTag](
+ sc: SparkContext,
+ rdds: Seq[RDD[T]]) extends UnionRDD[T](sc, rdds){
+ // TODO: We might need to guess a more reasonable thread pool size here
+ @transient val executorService = ThreadUtils.newDaemonFixedThreadPool(
+ Math.min(rdds.size, Runtime.getRuntime.availableProcessors()),
"ParallelUnionRDD")
+
+ override def getPartitions: Array[Partition] = {
+ // Calc partitions field for each RDD in parallel.
+ val rddPartitions = rdds.map {rdd =>
+ (rdd, executorService.submit(new Callable[Array[Partition]] {
+ override def call(): Array[Partition] = rdd.partitions
+ }))
+ }.map {case(r, f) => (r, f.get())}
+
+ val array = new Array[Partition](rddPartitions.map(_._2.length).sum)
--- End diff --
seems here still be the main thread, probably we even don't need to place
the `synchronized` in the `getPartitions`.
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