Github user wesm commented on a diff in the pull request:
https://github.com/apache/spark/pull/15821#discussion_r98075898
--- Diff: sql/core/src/main/scala/org/apache/spark/sql/Arrow.scala ---
@@ -0,0 +1,310 @@
+/*
+* 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 scala.collection.JavaConverters._
+import scala.language.implicitConversions
+
+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.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._
+
+object Arrow {
+
+ /**
+ * 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)
+ }
+}
+
+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)
+ override def setValue(row: InternalRow, ordinal: Int): Unit
+ = valueMutator.setSafe(count, bool2int(row.getBoolean(ordinal)))
+}
+
+private[sql] class ShortColumnWriter(allocator: BaseAllocator)
+ extends PrimitiveColumnWriter(allocator) {
+ override protected val valueVector: NullableSmallIntVector
+ = new NullableSmallIntVector("ShortValue", allocator)
+ override protected val valueMutator: NullableSmallIntVector#Mutator =
valueVector.getMutator
+
+ override def setNull(): Unit = valueMutator.setNull(count)
+ override def setValue(row: InternalRow, ordinal: Int): Unit
+ = valueMutator.setSafe(count, row.getShort(ordinal))
+}
+
+private[sql] class IntegerColumnWriter(allocator: BaseAllocator)
+ extends PrimitiveColumnWriter(allocator) {
+ override protected val valueVector: NullableIntVector
+ = new NullableIntVector("IntValue", allocator)
+ override protected val valueMutator: NullableIntVector#Mutator =
valueVector.getMutator
+
+ override def setNull(): Unit = valueMutator.setNull(count)
+ override def setValue(row: InternalRow, ordinal: Int): Unit
+ = valueMutator.setSafe(count, row.getInt(ordinal))
+}
+
+private[sql] class LongColumnWriter(allocator: BaseAllocator)
+ extends PrimitiveColumnWriter(allocator) {
+ override protected val valueVector: NullableBigIntVector
+ = new NullableBigIntVector("LongValue", allocator)
+ override protected val valueMutator: NullableBigIntVector#Mutator =
valueVector.getMutator
+
+ override def setNull(): Unit = valueMutator.setNull(count)
+ override def setValue(row: InternalRow, ordinal: Int): Unit
+ = valueMutator.setSafe(count, row.getLong(ordinal))
+}
+
+private[sql] class FloatColumnWriter(allocator: BaseAllocator)
+ extends PrimitiveColumnWriter(allocator) {
+ override protected val valueVector: NullableFloat4Vector
+ = new NullableFloat4Vector("FloatValue", allocator)
+ override protected val valueMutator: NullableFloat4Vector#Mutator =
valueVector.getMutator
+
+ override def setNull(): Unit = valueMutator.setNull(count)
+ override def setValue(row: InternalRow, ordinal: Int): Unit
+ = valueMutator.setSafe(count, row.getFloat(ordinal))
+}
+
+private[sql] class DoubleColumnWriter(allocator: BaseAllocator)
+ extends PrimitiveColumnWriter(allocator) {
+ override protected val valueVector: NullableFloat8Vector
+ = new NullableFloat8Vector("DoubleValue", allocator)
+ override protected val valueMutator: NullableFloat8Vector#Mutator =
valueVector.getMutator
+
+ override def setNull(): Unit = valueMutator.setNull(count)
+ override def setValue(row: InternalRow, ordinal: Int): Unit
+ = valueMutator.setSafe(count, row.getDouble(ordinal))
+}
+
+private[sql] class ByteColumnWriter(allocator: BaseAllocator)
+ extends PrimitiveColumnWriter(allocator) {
+ override protected val valueVector: NullableUInt1Vector
+ = new NullableUInt1Vector("ByteValue", allocator)
+ override protected val valueMutator: NullableUInt1Vector#Mutator =
valueVector.getMutator
+
+ override def setNull(): Unit = valueMutator.setNull(count)
+ override def setValue(row: InternalRow, ordinal: Int): Unit
+ = valueMutator.setSafe(count, row.getByte(ordinal))
+}
+
+private[sql] class UTF8StringColumnWriter(allocator: BaseAllocator)
+ extends PrimitiveColumnWriter(allocator) {
+ override protected val valueVector: NullableVarBinaryVector
+ = new NullableVarBinaryVector("UTF8StringValue", allocator)
+ override protected val valueMutator: NullableVarBinaryVector#Mutator =
valueVector.getMutator
+
+ override def setNull(): Unit = valueMutator.setNull(count)
+ override def setValue(row: InternalRow, ordinal: Int): Unit = {
+ val bytes = row.getUTF8String(ordinal).getBytes
+ valueMutator.setSafe(count, bytes, 0, bytes.length)
+ }
+}
+
+private[sql] class BinaryColumnWriter(allocator: BaseAllocator)
+ extends PrimitiveColumnWriter(allocator) {
+ override protected val valueVector: NullableVarBinaryVector
+ = new NullableVarBinaryVector("UTF8StringValue", allocator)
+ override protected val valueMutator: NullableVarBinaryVector#Mutator =
valueVector.getMutator
+
+ override def setNull(): Unit = valueMutator.setNull(count)
+ override def setValue(row: InternalRow, ordinal: Int): Unit = {
+ val bytes = row.getBinary(ordinal)
+ valueMutator.setSafe(count, bytes, 0, bytes.length)
+ }
+}
+
+private[sql] class DateColumnWriter(allocator: BaseAllocator)
+ extends PrimitiveColumnWriter(allocator) {
+ override protected val valueVector: NullableDateVector
+ = new NullableDateVector("DateValue", allocator)
+ override protected val valueMutator: NullableDateVector#Mutator =
valueVector.getMutator
+
+ override protected def setNull(): Unit = valueMutator.setNull(count)
+ override protected def setValue(row: InternalRow, ordinal: Int): Unit = {
+ valueMutator.setSafe(count, row.getInt(ordinal).toLong * 24 * 3600 *
1000)
--- End diff --
Can you add a comment explaining the difference between the value
representations (date ordinal vs. Joda-compatible milliseconds timestamp)?
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