Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/7456#discussion_r34970552
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/UnsafeRowSerializer.scala
---
@@ -0,0 +1,142 @@
+/*
+ * 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
+
+import java.io.{DataInputStream, DataOutputStream, OutputStream,
InputStream}
+import java.nio.ByteBuffer
+
+import scala.reflect.ClassTag
+
+import com.google.common.io.ByteStreams
+
+import org.apache.spark.serializer.{SerializationStream,
DeserializationStream, SerializerInstance, Serializer}
+import org.apache.spark.sql.catalyst.expressions.UnsafeRow
+import org.apache.spark.unsafe.PlatformDependent
+
+/**
+ * Serializer for serializing [[UnsafeRow]]s during shuffle. Since
UnsafeRows are already stored as
+ * bytes, this serializer simply copies those bytes to the underlying
output stream. When
+ * deserializing a stream of rows, instances of this serializer mutate and
return a single UnsafeRow
+ * instance that is backed by an on-heap byte array.
+ *
+ * Note that this serializer implements only the [[Serializer]] methods
that are used during
+ * shuffle, so certain [[SerializerInstance]] methods will throw
UnsupportedOperationException.
+ *
+ * This serializer does not support UnsafeRows that use
+ * [[org.apache.spark.sql.catalyst.util.ObjectPool]].
+ *
+ * @param numFields the number of fields in the row being serialized.
+ */
+private[sql] class UnsafeRowSerializer(numFields: Int) extends Serializer
with Serializable {
+ override def newInstance(): SerializerInstance = new
UnsafeRowSerializerInstance(numFields)
+ override private[spark] def supportsRelocationOfSerializedObjects:
Boolean = true
+}
+
+private class UnsafeRowSerializerInstance(numFields: Int) extends
SerializerInstance {
+
+ private[this] val EOF: Int = -1
+
+ override def serializeStream(out: OutputStream): SerializationStream =
new SerializationStream {
+ private[this] var writeBuffer: Array[Byte] = new Array[Byte](4096)
+ private[this] val dOut: DataOutputStream = new DataOutputStream(out)
+
+ override def writeValue[T: ClassTag](value: T): SerializationStream = {
+ val row = value.asInstanceOf[UnsafeRow]
+ assert(row.getPool == null, "UnsafeRowSerializer does not support
ObjectPool")
+ dOut.writeInt(row.getSizeInBytes)
+ var dataRemaining: Int = row.getSizeInBytes
+ val baseObject = row.getBaseObject
+ var rowReadPosition: Long = row.getBaseOffset
+ while (dataRemaining > 0) {
+ val toTransfer: Int = Math.min(writeBuffer.length, dataRemaining)
+ PlatformDependent.copyMemory(
+ baseObject,
+ rowReadPosition,
+ writeBuffer,
+ PlatformDependent.BYTE_ARRAY_OFFSET,
+ toTransfer)
+ out.write(writeBuffer, 0, toTransfer)
+ rowReadPosition += toTransfer
+ dataRemaining -= toTransfer
+ }
+ this
+ }
+ override def writeKey[T: ClassTag](key: T): SerializationStream = {
+ assert(key.isInstanceOf[Int])
+ this
+ }
+ override def writeAll[T: ClassTag](iter: Iterator[T]):
SerializationStream =
+ throw new UnsupportedOperationException
+ override def writeObject[T: ClassTag](t: T): SerializationStream =
+ throw new UnsupportedOperationException
+ override def flush(): Unit = dOut.flush()
+ override def close(): Unit = {
+ writeBuffer = null
+ dOut.writeInt(EOF)
+ dOut.close()
+ }
+ }
+
+ override def deserializeStream(in: InputStream): DeserializationStream =
{
+ new DeserializationStream {
+ private[this] val dIn: DataInputStream = new DataInputStream(in)
+ private[this] var rowBuffer: Array[Byte] = new Array[Byte](1024)
--- End diff --
why is the buffer here only 1024?
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