Github user icexelloss commented on a diff in the pull request:
https://github.com/apache/spark/pull/15821#discussion_r113730387
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/arrow/ArrowConverters.scala
---
@@ -0,0 +1,396 @@
+/*
+* 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.arrow
+
+import java.io.ByteArrayOutputStream
+import java.nio.channels.Channels
+
+import scala.collection.JavaConverters._
+
+import io.netty.buffer.ArrowBuf
+import org.apache.arrow.memory.{BufferAllocator, RootAllocator}
+import org.apache.arrow.vector._
+import org.apache.arrow.vector.BaseValueVector.BaseMutator
+import org.apache.arrow.vector.file._
+import org.apache.arrow.vector.schema.{ArrowFieldNode, ArrowRecordBatch}
+import org.apache.arrow.vector.types.{DateUnit, FloatingPointPrecision,
TimeUnit}
+import org.apache.arrow.vector.types.pojo.{ArrowType, Field, FieldType,
Schema}
+import org.apache.arrow.vector.util.ByteArrayReadableSeekableByteChannel
+
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.types._
+import org.apache.spark.util.Utils
+
+
+/**
+ * Store Arrow data in a form that can be serialized by Spark
+ */
+private[sql] class ArrowPayload(val batchBytes: Array[Byte]) extends
Serializable {
+
+ def this(batch: ArrowRecordBatch, schema: StructType, allocator:
BufferAllocator) = {
+ this(ArrowConverters.batchToByteArray(batch, schema, allocator))
+ }
+
+ def loadBatch(allocator: BufferAllocator): ArrowRecordBatch = {
+ ArrowConverters.byteArrayToBatch(batchBytes, allocator)
+ }
+}
+
+private[sql] object ArrowConverters {
+
+ /**
+ * Map a Spark DataType to ArrowType.
+ */
+ private[arrow] def sparkTypeToArrowType(dataType: DataType): ArrowType =
{
+ dataType match {
+ case BooleanType => ArrowType.Bool.INSTANCE
+ case ShortType => new ArrowType.Int(8 * ShortType.defaultSize, true)
+ case IntegerType => new ArrowType.Int(8 * IntegerType.defaultSize,
true)
+ case LongType => new ArrowType.Int(8 * LongType.defaultSize, true)
+ case FloatType => new
ArrowType.FloatingPoint(FloatingPointPrecision.SINGLE)
+ case DoubleType => new
ArrowType.FloatingPoint(FloatingPointPrecision.DOUBLE)
+ case ByteType => new ArrowType.Int(8, true)
+ case StringType => ArrowType.Utf8.INSTANCE
+ case BinaryType => ArrowType.Binary.INSTANCE
+ case _ => throw new UnsupportedOperationException(s"Unsupported data
type: $dataType")
+ }
+ }
+
+ /**
+ * Convert a Spark Dataset schema to Arrow schema.
+ */
+ private[arrow] def schemaToArrowSchema(schema: StructType): Schema = {
+ val arrowFields = schema.fields.map { f =>
+ new Field(f.name, f.nullable, sparkTypeToArrowType(f.dataType),
List.empty[Field].asJava)
+ }
+ new Schema(arrowFields.toList.asJava)
+ }
+
+ /**
+ * Maps Iterator from InternalRow to ArrowPayload
+ */
+ private[sql] def toPayloadIterator(
+ rowIter: Iterator[InternalRow],
+ schema: StructType): Iterator[ArrowPayload] = {
+ new Iterator[ArrowPayload] {
+ private val _allocator = new RootAllocator(Long.MaxValue)
+ private var _nextPayload = if (rowIter.nonEmpty) convert() else null
+
+ override def hasNext: Boolean = _nextPayload != null
+
+ override def next(): ArrowPayload = {
+ val obj = _nextPayload
+ if (hasNext) {
+ if (rowIter.hasNext) {
+ _nextPayload = convert()
+ } else {
+ _allocator.close()
+ _nextPayload = null
+ }
+ }
+ obj
+ }
+
+ private def convert(): ArrowPayload = {
+ val batch = internalRowIterToArrowBatch(rowIter, schema,
_allocator)
+ new ArrowPayload(batch, schema, _allocator)
+ }
+ }
+ }
+
+ /**
+ * Iterate over InternalRows and write to an ArrowRecordBatch.
+ */
+ private def internalRowIterToArrowBatch(
+ rowIter: Iterator[InternalRow],
+ schema: StructType,
+ allocator: BufferAllocator): ArrowRecordBatch = {
+
+ val columnWriters = schema.fields.zipWithIndex.map { case (field,
ordinal) =>
+ ColumnWriter(ordinal, allocator, field.dataType).init()
+ }
+
+ val writerLength = columnWriters.length
+ while (rowIter.hasNext) {
+ val row = rowIter.next()
+ var i = 0
+ while (i < writerLength) {
+ columnWriters(i).write(row)
+ i += 1
+ }
+ }
+
+ val (fieldNodes, bufferArrays) = columnWriters.map(_.finish()).unzip
+ val buffers = bufferArrays.flatten
+
+ val rowLength = if (fieldNodes.nonEmpty) fieldNodes.head.getLength
else 0
+ val recordBatch = new ArrowRecordBatch(rowLength,
+ fieldNodes.toList.asJava, buffers.toList.asJava)
+
+ buffers.foreach(_.release())
+ recordBatch
+ }
+
+ /**
+ * Convert an ArrowRecordBatch to a byte array and close batch
+ */
+ private[arrow] def batchToByteArray(
--- End diff --
Maybe useful to document that the `batch` becomes invalid after calling
this function and should not be used further.
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