Github user zsxwing commented on a diff in the pull request:
https://github.com/apache/spark/pull/19925#discussion_r156530920
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/continuous/ContinuousRateStreamSource.scala
---
@@ -0,0 +1,155 @@
+/*
+ * 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.streaming.continuous
+
+import scala.collection.JavaConverters._
+
+import org.json4s.DefaultFormats
+import org.json4s.jackson.Serialization
+
+import org.apache.spark.sql.Row
+import org.apache.spark.sql.catalyst.expressions.UnsafeRow
+import org.apache.spark.sql.catalyst.util.DateTimeUtils
+import org.apache.spark.sql.execution.streaming._
+import org.apache.spark.sql.sources.v2.{ContinuousReadSupport,
DataSourceV2, DataSourceV2Options}
+import org.apache.spark.sql.sources.v2.reader._
+import org.apache.spark.sql.types.{LongType, StructField, StructType,
TimestampType}
+
+object ContinuousRateStreamSource {
+ val NUM_PARTITIONS = "numPartitions"
+ val ROWS_PER_SECOND = "rowsPerSecond"
+}
+
+case class ContinuousRateStreamOffset(partitionToStartValue: Map[Int,
Long]) extends Offset {
+ implicit val defaultFormats: DefaultFormats = DefaultFormats
+ override val json = Serialization.write(partitionToStartValue)
+}
+
+case class ContinuousRateStreamPartitionOffset(partition: Int, start:
Long) extends PartitionOffset
+
+class ContinuousRateStreamReader(options: DataSourceV2Options)
+ extends ContinuousReader {
+ implicit val defaultFormats: DefaultFormats = DefaultFormats
+
+ val numPartitions =
options.get(ContinuousRateStreamSource.NUM_PARTITIONS).orElse("5").toInt
+ val rowsPerSecond =
options.get(ContinuousRateStreamSource.ROWS_PER_SECOND).orElse("6").toLong
+
+ override def mergeOffsets(offsets: Array[PartitionOffset]): Offset = {
+ assert(offsets.length == numPartitions)
+ val tuples = offsets.map {
+ case ContinuousRateStreamPartitionOffset(p, s) => p -> s
+ }
+ ContinuousRateStreamOffset(Map(tuples: _*))
+ }
+
+ override def deserializeOffset(json: String): Offset = {
+ ContinuousRateStreamOffset(Serialization.read[Map[Int, Long]](json))
+ }
+
+ override def readSchema(): StructType = {
+ StructType(
+ StructField("timestamp", TimestampType, false) ::
+ StructField("value", LongType, false) :: Nil)
+ }
+
+ private var offset: java.util.Optional[Offset] = _
+
+ override def setOffset(offset: java.util.Optional[Offset]): Unit = {
+ this.offset = offset
+ }
+
+ override def getStartOffset(): Offset = offset.get()
+
+ override def createReadTasks(): java.util.List[ReadTask[Row]] = {
+ val partitionStartMap = Option(offset.orElse(null)).map {
+ case o: ContinuousRateStreamOffset => o.partitionToStartValue
+ case s: SerializedOffset => Serialization.read[Map[Int,
Long]](s.json)
--- End diff --
A v2 reader should never see `SerializedOffset`. Right? The engine is
supposed to call `deserializeOffset` to get the real offset object.
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