Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/20933#discussion_r179517717
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/FileReaderFactory.scala
---
@@ -0,0 +1,50 @@
+/*
+ * 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.execution.datasources.v2
+
+import org.apache.spark.TaskContext
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.execution.datasources.{FilePartition,
FilePartitionUtil, PartitionedFile}
+import org.apache.spark.sql.sources.v2.reader.{DataReader,
DataReaderFactory}
+
+case class FileReaderFactory[T](
+ file: FilePartition,
+ readFunction: (PartitionedFile) => Iterator[InternalRow],
+ ignoreCorruptFiles: Boolean = false,
+ ignoreMissingFiles: Boolean = false)
+ extends DataReaderFactory[T] {
+ override def createDataReader(): DataReader[T] = {
+ val taskContext = TaskContext.get()
+ val iter = FilePartitionUtil.compute(file, taskContext, readFunction,
+ ignoreCorruptFiles, ignoreMissingFiles)
+ InternalRowDataReader[T](iter)
+ }
+
+ override def preferredLocations(): Array[String] = {
+ FilePartitionUtil.getPreferredLocations(file)
+ }
+}
+
+case class InternalRowDataReader[T](iter: Iterator[InternalRow])
+ extends DataReader[T] {
+ override def next(): Boolean = iter.hasNext
+
+ override def get(): T = iter.next().asInstanceOf[T]
--- End diff --
explain why this works, i.e. we use type erase hack to return columnar
batch.
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