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[SPARK-11810][SQL] Java-based encoder for opaque types in Datasets.
This patch refactors the existing Kryo encoder expressions and adds support for Java serialization. Author: Reynold Xin <rxin@databricks.com> Closes #9802 from rxin/SPARK-11810.
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‎sql/catalyst/src/main/scala/org/apache/spark/sql/Encoder.scala‎

Lines changed: 31 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -20,7 +20,7 @@ package org.apache.spark.sql
2020
import scala.reflect.{ClassTag, classTag}
2121

2222
import org.apache.spark.sql.catalyst.encoders.{ExpressionEncoder, encoderFor}
23-
import org.apache.spark.sql.catalyst.expressions.{DeserializeWithKryo, BoundReference, SerializeWithKryo}
23+
import org.apache.spark.sql.catalyst.expressions.{DecodeUsingSerializer, BoundReference, EncodeUsingSerializer}
2424
import org.apache.spark.sql.types._
2525

2626
/**
@@ -43,28 +43,49 @@ trait Encoder[T] extends Serializable {
4343
*/
4444
object Encoders {
4545

46-
/**
47-
* (Scala-specific) Creates an encoder that serializes objects of type T using Kryo.
48-
* This encoder maps T into a single byte array (binary) field.
49-
*/
50-
def kryo[T: ClassTag]: Encoder[T] = {
51-
val ser = SerializeWithKryo(BoundReference(0, ObjectType(classOf[AnyRef]), nullable = true))
52-
val deser = DeserializeWithKryo[T](BoundReference(0, BinaryType, nullable = true), classTag[T])
46+
/** A way to construct encoders using generic serializers. */
47+
private def genericSerializer[T: ClassTag](useKryo: Boolean): Encoder[T] = {
5348
ExpressionEncoder[T](
5449
schema = new StructType().add("value", BinaryType),
5550
flat = true,
56-
toRowExpressions = Seq(ser),
57-
fromRowExpression = deser,
51+
toRowExpressions = Seq(
52+
EncodeUsingSerializer(
53+
BoundReference(0, ObjectType(classOf[AnyRef]), nullable = true), kryo = useKryo)),
54+
fromRowExpression =
55+
DecodeUsingSerializer[T](
56+
BoundReference(0, BinaryType, nullable = true), classTag[T], kryo = useKryo),
5857
clsTag = classTag[T]
5958
)
6059
}
6160

61+
/**
62+
* (Scala-specific) Creates an encoder that serializes objects of type T using Kryo.
63+
* This encoder maps T into a single byte array (binary) field.
64+
*/
65+
def kryo[T: ClassTag]: Encoder[T] = genericSerializer(useKryo = true)
66+
6267
/**
6368
* Creates an encoder that serializes objects of type T using Kryo.
6469
* This encoder maps T into a single byte array (binary) field.
6570
*/
6671
def kryo[T](clazz: Class[T]): Encoder[T] = kryo(ClassTag[T](clazz))
6772

73+
/**
74+
* (Scala-specific) Creates an encoder that serializes objects of type T using generic Java
75+
* serialization. This encoder maps T into a single byte array (binary) field.
76+
*
77+
* Note that this is extremely inefficient and should only be used as the last resort.
78+
*/
79+
def javaSerialization[T: ClassTag]: Encoder[T] = genericSerializer(useKryo = false)
80+
81+
/**
82+
* Creates an encoder that serializes objects of type T using generic Java serialization.
83+
* This encoder maps T into a single byte array (binary) field.
84+
*
85+
* Note that this is extremely inefficient and should only be used as the last resort.
86+
*/
87+
def javaSerialization[T](clazz: Class[T]): Encoder[T] = javaSerialization(ClassTag[T](clazz))
88+
6889
def BOOLEAN: Encoder[java.lang.Boolean] = ExpressionEncoder(flat = true)
6990
def BYTE: Encoder[java.lang.Byte] = ExpressionEncoder(flat = true)
7091
def SHORT: Encoder[java.lang.Short] = ExpressionEncoder(flat = true)

‎sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects.scala‎

Lines changed: 43 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -21,7 +21,7 @@ import scala.language.existentials
2121
import scala.reflect.ClassTag
2222

2323
import org.apache.spark.SparkConf
24-
import org.apache.spark.serializer.{KryoSerializerInstance, KryoSerializer}
24+
import org.apache.spark.serializer._
2525
import org.apache.spark.sql.Row
2626
import org.apache.spark.sql.catalyst.analysis.SimpleAnalyzer
2727
import org.apache.spark.sql.catalyst.plans.logical.{Project, LocalRelation}
@@ -517,29 +517,39 @@ case class GetInternalRowField(child: Expression, ordinal: Int, dataType: DataTy
517517
}
518518
}
519519

520-
/** Serializes an input object using Kryo serializer. */
521-
case class SerializeWithKryo(child: Expression) extends UnaryExpression {
520+
/**
521+
* Serializes an input object using a generic serializer (Kryo or Java).
522+
* @param kryo if true, use Kryo. Otherwise, use Java.
523+
*/
524+
case class EncodeUsingSerializer(child: Expression, kryo: Boolean) extends UnaryExpression {
522525

523526
override def eval(input: InternalRow): Any =
524527
throw new UnsupportedOperationException("Only code-generated evaluation is supported")
525528

526529
override protected def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): String = {
527-
val input = child.gen(ctx)
528-
val kryo = ctx.freshName("kryoSerializer")
529-
val kryoClass = classOf[KryoSerializer].getName
530-
val kryoInstanceClass = classOf[KryoSerializerInstance].getName
531-
val sparkConfClass = classOf[SparkConf].getName
530+
// Code to initialize the serializer.
531+
val serializer = ctx.freshName("serializer")
532+
val (serializerClass, serializerInstanceClass) = {
533+
if (kryo) {
534+
(classOf[KryoSerializer].getName, classOf[KryoSerializerInstance].getName)
535+
} else {
536+
(classOf[JavaSerializer].getName, classOf[JavaSerializerInstance].getName)
537+
}
538+
}
539+
val sparkConf = s"new ${classOf[SparkConf].getName}()"
532540
ctx.addMutableState(
533-
kryoInstanceClass,
534-
kryo,
535-
s"$kryo = ($kryoInstanceClass) new $kryoClass(new $sparkConfClass()).newInstance();")
541+
serializerInstanceClass,
542+
serializer,
543+
s"$serializer = ($serializerInstanceClass) new $serializerClass($sparkConf).newInstance();")
536544

545+
// Code to serialize.
546+
val input = child.gen(ctx)
537547
s"""
538548
${input.code}
539549
final boolean ${ev.isNull} = ${input.isNull};
540550
${ctx.javaType(dataType)} ${ev.value} = ${ctx.defaultValue(dataType)};
541551
if (!${ev.isNull}) {
542-
${ev.value} = $kryo.serialize(${input.value}, null).array();
552+
${ev.value} = $serializer.serialize(${input.value}, null).array();
543553
}
544554
"""
545555
}
@@ -548,29 +558,38 @@ case class SerializeWithKryo(child: Expression) extends UnaryExpression {
548558
}
549559

550560
/**
551-
* Deserializes an input object using Kryo serializer. Note that the ClassTag is not an implicit
552-
* parameter because TreeNode cannot copy implicit parameters.
561+
* Serializes an input object using a generic serializer (Kryo or Java). Note that the ClassTag
562+
* is not an implicit parameter because TreeNode cannot copy implicit parameters.
563+
* @param kryo if true, use Kryo. Otherwise, use Java.
553564
*/
554-
case class DeserializeWithKryo[T](child: Expression, tag: ClassTag[T]) extends UnaryExpression {
565+
case class DecodeUsingSerializer[T](child: Expression, tag: ClassTag[T], kryo: Boolean)
566+
extends UnaryExpression {
555567

556568
override protected def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): String = {
557-
val input = child.gen(ctx)
558-
val kryo = ctx.freshName("kryoSerializer")
559-
val kryoClass = classOf[KryoSerializer].getName
560-
val kryoInstanceClass = classOf[KryoSerializerInstance].getName
561-
val sparkConfClass = classOf[SparkConf].getName
569+
// Code to initialize the serializer.
570+
val serializer = ctx.freshName("serializer")
571+
val (serializerClass, serializerInstanceClass) = {
572+
if (kryo) {
573+
(classOf[KryoSerializer].getName, classOf[KryoSerializerInstance].getName)
574+
} else {
575+
(classOf[JavaSerializer].getName, classOf[JavaSerializerInstance].getName)
576+
}
577+
}
578+
val sparkConf = s"new ${classOf[SparkConf].getName}()"
562579
ctx.addMutableState(
563-
kryoInstanceClass,
564-
kryo,
565-
s"$kryo = ($kryoInstanceClass) new $kryoClass(new $sparkConfClass()).newInstance();")
580+
serializerInstanceClass,
581+
serializer,
582+
s"$serializer = ($serializerInstanceClass) new $serializerClass($sparkConf).newInstance();")
566583

584+
// Code to serialize.
585+
val input = child.gen(ctx)
567586
s"""
568587
${input.code}
569588
final boolean ${ev.isNull} = ${input.isNull};
570589
${ctx.javaType(dataType)} ${ev.value} = ${ctx.defaultValue(dataType)};
571590
if (!${ev.isNull}) {
572591
${ev.value} = (${ctx.javaType(dataType)})
573-
$kryo.deserialize(java.nio.ByteBuffer.wrap(${input.value}), null);
592+
$serializer.deserialize(java.nio.ByteBuffer.wrap(${input.value}), null);
574593
}
575594
"""
576595
}

‎sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/FlatEncoderSuite.scala‎

Lines changed: 22 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -76,17 +76,34 @@ class FlatEncoderSuite extends ExpressionEncoderSuite {
7676
// Kryo encoders
7777
encodeDecodeTest(
7878
"hello",
79-
Encoders.kryo[String].asInstanceOf[ExpressionEncoder[String]],
79+
encoderFor(Encoders.kryo[String]),
8080
"kryo string")
8181
encodeDecodeTest(
82-
new NotJavaSerializable(15),
83-
Encoders.kryo[NotJavaSerializable].asInstanceOf[ExpressionEncoder[NotJavaSerializable]],
82+
new KryoSerializable(15),
83+
encoderFor(Encoders.kryo[KryoSerializable]),
8484
"kryo object serialization")
85+
86+
// Java encoders
87+
encodeDecodeTest(
88+
"hello",
89+
encoderFor(Encoders.javaSerialization[String]),
90+
"java string")
91+
encodeDecodeTest(
92+
new JavaSerializable(15),
93+
encoderFor(Encoders.javaSerialization[JavaSerializable]),
94+
"java object serialization")
8595
}
8696

97+
/** For testing Kryo serialization based encoder. */
98+
class KryoSerializable(val value: Int) {
99+
override def equals(other: Any): Boolean = {
100+
this.value == other.asInstanceOf[KryoSerializable].value
101+
}
102+
}
87103

88-
class NotJavaSerializable(val value: Int) {
104+
/** For testing Java serialization based encoder. */
105+
class JavaSerializable(val value: Int) extends Serializable {
89106
override def equals(other: Any): Boolean = {
90-
this.value == other.asInstanceOf[NotJavaSerializable].value
107+
this.value == other.asInstanceOf[JavaSerializable].value
91108
}
92109
}

‎sql/core/src/test/scala/org/apache/spark/sql/DatasetSuite.scala‎

Lines changed: 34 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -357,15 +357,15 @@ class DatasetSuite extends QueryTest with SharedSQLContext {
357357
assert(ds.toString == "[_1: int, _2: int]")
358358
}
359359

360-
test("kryo encoder") {
360+
test("Kryo encoder") {
361361
implicit val kryoEncoder = Encoders.kryo[KryoData]
362362
val ds = Seq(KryoData(1), KryoData(2)).toDS()
363363

364364
assert(ds.groupBy(p => p).count().collect().toSeq ==
365365
Seq((KryoData(1), 1L), (KryoData(2), 1L)))
366366
}
367367

368-
test("kryo encoder self join") {
368+
test("Kryo encoder self join") {
369369
implicit val kryoEncoder = Encoders.kryo[KryoData]
370370
val ds = Seq(KryoData(1), KryoData(2)).toDS()
371371
assert(ds.joinWith(ds, lit(true)).collect().toSet ==
@@ -375,6 +375,25 @@ class DatasetSuite extends QueryTest with SharedSQLContext {
375375
(KryoData(2), KryoData(1)),
376376
(KryoData(2), KryoData(2))))
377377
}
378+
379+
test("Java encoder") {
380+
implicit val kryoEncoder = Encoders.javaSerialization[JavaData]
381+
val ds = Seq(JavaData(1), JavaData(2)).toDS()
382+
383+
assert(ds.groupBy(p => p).count().collect().toSeq ==
384+
Seq((JavaData(1), 1L), (JavaData(2), 1L)))
385+
}
386+
387+
ignore("Java encoder self join") {
388+
implicit val kryoEncoder = Encoders.javaSerialization[JavaData]
389+
val ds = Seq(JavaData(1), JavaData(2)).toDS()
390+
assert(ds.joinWith(ds, lit(true)).collect().toSet ==
391+
Set(
392+
(JavaData(1), JavaData(1)),
393+
(JavaData(1), JavaData(2)),
394+
(JavaData(2), JavaData(1)),
395+
(JavaData(2), JavaData(2))))
396+
}
378397
}
379398

380399

@@ -406,3 +425,16 @@ class KryoData(val a: Int) {
406425
object KryoData {
407426
def apply(a: Int): KryoData = new KryoData(a)
408427
}
428+
429+
/** Used to test Java encoder. */
430+
class JavaData(val a: Int) extends Serializable {
431+
override def equals(other: Any): Boolean = {
432+
a == other.asInstanceOf[JavaData].a
433+
}
434+
override def hashCode: Int = a
435+
override def toString: String = s"JavaData($a)"
436+
}
437+
438+
object JavaData {
439+
def apply(a: Int): JavaData = new JavaData(a)
440+
}

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