[GitHub] [iceberg] rdblue commented on a change in pull request #2800: Spark: Parallelize initializing readTasks when localityPreferred is true

[GitBox <gi...@apache.org>]

rdblue commented on a change in pull request #2800:
URL: https://github.com/apache/iceberg/pull/2800#discussion_r667179215



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File path: spark2/src/main/java/org/apache/iceberg/spark/source/Reader.java
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@@ -206,11 +219,14 @@ public StructType readSchema() {
     Broadcast<Table> tableBroadcast = sparkContext.broadcast(SerializableTable.copyOf(table));
 
     List<InputPartition<ColumnarBatch>> readTasks = Lists.newArrayList();
-    for (CombinedScanTask task : tasks()) {
-      readTasks.add(new ReadTask<>(
-          task, tableBroadcast, expectedSchemaString, caseSensitive,
-          localityPreferred, new BatchReaderFactory(batchSize)));
-    }
+    Tasks.foreach(tasks())
+        .stopOnFailure()
+        .executeWith(readTasksInitExecutorService)
+        .run(task -> {
+          readTasks.add(new ReadTask<>(

Review comment:
       This can't alter `readTasks` from multiple threads because array lists aren't thread-safe.




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