[SPARK-23099][SS] Migrate foreach sink to DataSourceV2

sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/sources/ForeachWriterProvider.scala

@@ -0,0 +1,111 @@
+/*
+ * 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.sources
+
+import org.apache.spark.sql.{Encoder, ForeachWriter, SparkSession}
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.encoders.{encoderFor, ExpressionEncoder}
+import org.apache.spark.sql.sources.v2.{DataSourceOptions, StreamWriteSupport}
+import org.apache.spark.sql.sources.v2.writer.{DataWriter, DataWriterFactory, SupportsWriteInternalRow, WriterCommitMessage}
+import org.apache.spark.sql.sources.v2.writer.streaming.StreamWriter
+import org.apache.spark.sql.streaming.OutputMode
+import org.apache.spark.sql.types.StructType
+
+/**
+ * A [[org.apache.spark.sql.sources.v2.DataSourceV2]] for forwarding data into the specified
+ * [[ForeachWriter]].
+ *
+ * @param writer The [[ForeachWriter]] to process all data.
+ * @tparam T The expected type of the sink.
+ */
+case class ForeachWriterProvider[T: Encoder](writer: ForeachWriter[T]) extends StreamWriteSupport {
+  override def createStreamWriter(
+      queryId: String,
+      schema: StructType,
+      mode: OutputMode,
+      options: DataSourceOptions): StreamWriter = {
+    new StreamWriter with SupportsWriteInternalRow {
+      override def commit(epochId: Long, messages: Array[WriterCommitMessage]): Unit = {}
+      override def abort(epochId: Long, messages: Array[WriterCommitMessage]): Unit = {}
+
+      override def createInternalRowWriterFactory(): DataWriterFactory[InternalRow] = {
+        val encoder = encoderFor[T].resolveAndBind(
+          schema.toAttributes,
+          SparkSession.getActiveSession.get.sessionState.analyzer)
+        ForeachWriterFactory(writer, encoder)
+      }
+
+      override def toString: String = "ForeachSink"
+    }
+  }
+}
+
+case class ForeachWriterFactory[T: Encoder](
+    writer: ForeachWriter[T],
+    encoder: ExpressionEncoder[T])
+  extends DataWriterFactory[InternalRow] {
+  override def createDataWriter(
+      partitionId: Int,
+      attemptNumber: Int,
+      epochId: Long): ForeachDataWriter[T] = {
+    new ForeachDataWriter(writer, encoder, partitionId, epochId)
+  }
+}
+
+/**
+ * A [[DataWriter]] which writes data in this partition to a [[ForeachWriter]].
+ * @param writer The [[ForeachWriter]] to process all data.
+ * @param encoder An encoder which can convert [[InternalRow]] to the required type [[T]]
+ * @param partitionId
+ * @param epochId
+ * @tparam T The type expected by the writer.
+ */
+class ForeachDataWriter[T : Encoder](
+    writer: ForeachWriter[T],
+    encoder: ExpressionEncoder[T],
+    partitionId: Int,
+    epochId: Long)
+  extends DataWriter[InternalRow] {
+
+  // If open returns false, we should skip writing rows.
+  private val opened = writer.open(partitionId, epochId)
+
+  override def write(record: InternalRow): Unit = {
+    if (!opened) return
+
+    try {
+      writer.process(encoder.fromRow(record))
+    } catch {
+      case t: Throwable =>
+        writer.close(t)
+        throw t
+    }
+  }
+
+  override def commit(): WriterCommitMessage = {
+    writer.close(null)
+    ForeachWriterCommitMessage
+  }
+
+  override def abort(): Unit = {}
+}
+
+/**
+ * An empty [[WriterCommitMessage]]. [[ForeachWriter]] implementations have no global coordination.
+ */
+case object ForeachWriterCommitMessage extends WriterCommitMessage

sql/core/src/main/scala/org/apache/spark/sql/streaming/DataStreamWriter.scala

@@ -28,7 +28,7 @@ import org.apache.spark.sql.execution.command.DDLUtils
 import org.apache.spark.sql.execution.datasources.DataSource
 import org.apache.spark.sql.execution.streaming._
 import org.apache.spark.sql.execution.streaming.continuous.ContinuousTrigger
-import org.apache.spark.sql.execution.streaming.sources.{MemoryPlanV2, MemorySinkV2}
+import org.apache.spark.sql.execution.streaming.sources.{ForeachWriterProvider, MemoryPlanV2, MemorySinkV2}
 import org.apache.spark.sql.sources.v2.StreamWriteSupport
 
 /**
@@ -269,7 +269,7 @@ final class DataStreamWriter[T] private[sql](ds: Dataset[T]) {
       query
     } else if (source == "foreach") {
       assertNotPartitioned("foreach")
-      val sink = new ForeachSink[T](foreachWriter)(ds.exprEnc)
+      val sink = new ForeachWriterProvider[T](foreachWriter)(ds.exprEnc)
       df.sparkSession.sessionState.streamingQueryManager.startQuery(
         extraOptions.get("queryName"),
         extraOptions.get("checkpointLocation"),