[GitHub] spark pull request #15821: [SPARK-13534][WIP][PySpark] Using Apache Arrow to...

[viirya <gi...@git.apache.org>]

Github user viirya commented on a diff in the pull request:

    https://github.com/apache/spark/pull/15821#discussion_r101214262
  
    --- Diff: sql/core/src/main/scala/org/apache/spark/sql/ArrowConverters.scala ---
    @@ -0,0 +1,360 @@
    +/*
    +* 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
    +
    +import java.io.ByteArrayOutputStream
    +import java.nio.channels.Channels
    +
    +import scala.collection.JavaConverters._
    +
    +import io.netty.buffer.ArrowBuf
    +import org.apache.arrow.memory.{BaseAllocator, RootAllocator}
    +import org.apache.arrow.vector._
    +import org.apache.arrow.vector.BaseValueVector.BaseMutator
    +import org.apache.arrow.vector.file.ArrowWriter
    +import org.apache.arrow.vector.schema.{ArrowFieldNode, ArrowRecordBatch}
    +import org.apache.arrow.vector.types.{FloatingPointPrecision, TimeUnit}
    +import org.apache.arrow.vector.types.pojo.{ArrowType, Field, Schema}
    +
    +import org.apache.spark.sql.catalyst.InternalRow
    +import org.apache.spark.sql.types._
    +
    +/**
    + * Intermediate data structure returned from Arrow conversions
    + */
    +private[sql] abstract class ArrowPayload extends Iterator[ArrowRecordBatch]
    +
    +/**
    + * Class that wraps an Arrow RootAllocator used in conversion
    + */
    +private[sql] class ArrowConverters {
    +  private val _allocator = new RootAllocator(Long.MaxValue)
    +
    +  private[sql] def allocator: RootAllocator = _allocator
    +
    +  private class ArrowStaticPayload(batches: ArrowRecordBatch*) extends ArrowPayload {
    +    private val iter = batches.iterator
    +
    +    override def next(): ArrowRecordBatch = iter.next()
    +    override def hasNext: Boolean = iter.hasNext
    +  }
    +
    +  def internalRowsToPayload(rows: Array[InternalRow], schema: StructType): ArrowPayload = {
    +    val batch = ArrowConverters.internalRowsToArrowRecordBatch(rows, schema, allocator)
    +    new ArrowStaticPayload(batch)
    +  }
    +}
    +
    +private[sql] object ArrowConverters {
    +
    +  /**
    +   * Map a Spark Dataset type to ArrowType.
    +   */
    +  private[sql] 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 DateType => ArrowType.Date.INSTANCE
    +      case TimestampType => new ArrowType.Timestamp(TimeUnit.MILLISECOND)
    +      case _ => throw new UnsupportedOperationException(s"Unsupported data type: $dataType")
    +    }
    +  }
    +
    +  /**
    +   * Transfer an array of InternalRow to an ArrowRecordBatch.
    +   */
    +  private[sql] def internalRowsToArrowRecordBatch(
    +      rows: Array[InternalRow],
    +      schema: StructType,
    +      allocator: RootAllocator): ArrowRecordBatch = {
    +    val fieldAndBuf = schema.fields.zipWithIndex.map { case (field, ordinal) =>
    +      internalRowToArrowBuf(rows, ordinal, field, allocator)
    +    }.unzip
    +    val fieldNodes = fieldAndBuf._1.flatten
    +    val buffers = fieldAndBuf._2.flatten
    +
    +    val recordBatch = new ArrowRecordBatch(rows.length,
    +      fieldNodes.toList.asJava, buffers.toList.asJava)
    +
    +    buffers.foreach(_.release())
    +    recordBatch
    +  }
    +
    +  /**
    +   * Write a Field from array of InternalRow to an ArrowBuf.
    +   */
    +  private def internalRowToArrowBuf(
    +      rows: Array[InternalRow],
    +      ordinal: Int,
    +      field: StructField,
    +      allocator: RootAllocator): (Array[ArrowFieldNode], Array[ArrowBuf]) = {
    +    val numOfRows = rows.length
    +    val columnWriter = ColumnWriter(allocator, field.dataType)
    +    columnWriter.init(numOfRows)
    +    var index = 0
    +
    +    while(index < numOfRows) {
    +      val row = rows(index)
    +      if (row.isNullAt(ordinal)) {
    +        columnWriter.writeNull()
    +      } else {
    +        columnWriter.write(row, ordinal)
    +      }
    +      index += 1
    +    }
    +
    +    val (arrowFieldNodes, arrowBufs) = columnWriter.finish()
    +    (arrowFieldNodes.toArray, arrowBufs.toArray)
    +  }
    +
    +  /**
    +   * Convert a Spark Dataset schema to Arrow schema.
    +   */
    +  private[sql] 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)
    +  }
    +
    +  /**
    +   * Write an ArrowPayload to a byte array
    +   */
    +  private[sql] def payloadToByteArray(payload: ArrowPayload, schema: StructType): Array[Byte] = {
    +    val arrowSchema = ArrowConverters.schemaToArrowSchema(schema)
    +    val out = new ByteArrayOutputStream()
    +    val writer = new ArrowWriter(Channels.newChannel(out), arrowSchema)
    +    try {
    +      payload.foreach(writer.writeRecordBatch)
    +    } catch {
    +      case e: Exception =>
    +        throw e
    +    } finally {
    +      writer.close()
    +      payload.foreach(_.close())
    +    }
    +    out.toByteArray
    +  }
    +}
    +
    +private[sql] trait ColumnWriter {
    +  def init(initialSize: Int): Unit
    +  def writeNull(): Unit
    +  def write(row: InternalRow, ordinal: Int): Unit
    +
    +  /**
    +   * Clear the column writer and return the ArrowFieldNode and ArrowBuf.
    +   * This should be called only once after all the data is written.
    +   */
    +  def finish(): (Seq[ArrowFieldNode], Seq[ArrowBuf])
    +}
    +
    +/**
    + * Base class for flat arrow column writer, i.e., column without children.
    + */
    +private[sql] abstract class PrimitiveColumnWriter(protected val allocator: BaseAllocator)
    +    extends ColumnWriter {
    +  protected def valueVector: BaseDataValueVector
    +  protected def valueMutator: BaseMutator
    +
    +  protected def setNull(): Unit
    +  protected def setValue(row: InternalRow, ordinal: Int): Unit
    +
    +  protected var count = 0
    +  protected var nullCount = 0
    +
    +  override def init(initialSize: Int): Unit = {
    +    valueVector.allocateNew()
    +  }
    +
    +  override def writeNull(): Unit = {
    +    setNull()
    +    nullCount += 1
    +    count += 1
    +  }
    +
    +  override def write(row: InternalRow, ordinal: Int): Unit = {
    +    setValue(row, ordinal)
    +    count += 1
    +  }
    +
    +  override def finish(): (Seq[ArrowFieldNode], Seq[ArrowBuf]) = {
    +    valueMutator.setValueCount(count)
    +    val fieldNode = new ArrowFieldNode(count, nullCount)
    +    val valueBuffers: Seq[ArrowBuf] = valueVector.getBuffers(true)
    +    (List(fieldNode), valueBuffers)
    +  }
    +}
    +
    +private[sql] class BooleanColumnWriter(allocator: BaseAllocator)
    +    extends PrimitiveColumnWriter(allocator) {
    +  private def bool2int(b: Boolean): Int = if (b) 1 else 0
    +
    +  override protected val valueVector: NullableBitVector
    +    = new NullableBitVector("BooleanValue", allocator)
    +  override protected val valueMutator: NullableBitVector#Mutator = valueVector.getMutator
    +
    +  override def setNull(): Unit = valueMutator.setNull(count)
    --- End diff --
    
    setNull and setValue should be protected.


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