Sketch writing with V2 API

src/main/scala/uk/co/gresearch/spark/dgraph/connector/TableBase.scala

@@ -22,7 +22,7 @@ import java.util
 import java.util.UUID
 import scala.jdk.CollectionConverters._
 
-trait TableBase extends Table with SupportsRead{
+trait TableBase extends Table with SupportsRead {
 
   val cid: UUID
 

src/main/scala/uk/co/gresearch/spark/dgraph/connector/TripleBatchWrite.scala

@@ -0,0 +1,16 @@
+package uk.co.gresearch.spark.dgraph.connector
+
+import org.apache.spark.sql.connector.write.{BatchWrite, DataWriterFactory, PhysicalWriteInfo, WriterCommitMessage}
+import org.apache.spark.sql.types.StructType
+import uk.co.gresearch.spark.dgraph.connector.model.GraphTableModel
+
+case class TripleBatchWrite(schema: StructType, model: GraphTableModel) extends BatchWrite {
+  override def createBatchWriterFactory(physicalWriteInfo: PhysicalWriteInfo): DataWriterFactory =
+    TripleDataWriterFactory(schema, model)
+
+  override def commit(writerCommitMessages: Array[WriterCommitMessage]): Unit = {
+    writerCommitMessages.foreach(msg => Console.println(s"Committed $msg"))
+  }
+
+  override def abort(writerCommitMessages: Array[WriterCommitMessage]): Unit = { }
+}

src/main/scala/uk/co/gresearch/spark/dgraph/connector/TripleDataWriter.scala

@@ -0,0 +1,28 @@
+package uk.co.gresearch.spark.dgraph.connector
+
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.connector.write.{DataWriter, WriterCommitMessage}
+import org.apache.spark.sql.types.StructType
+import uk.co.gresearch.spark.dgraph.connector.model.GraphTableModel
+
+case class TripleDataWriter(schema: StructType, model: GraphTableModel) extends DataWriter[InternalRow] {
+  var triples = 0L
+
+  override def write(row: InternalRow): Unit = {
+    // Console.println(s"Writing row: $row")
+    triples = triples + 1
+  }
+
+  override def commit(): WriterCommitMessage = {
+    val msg: WriterCommitMessage = new WriterCommitMessage {
+      val name: String = s"$triples triples (${Thread.currentThread().getName})"
+      override def toString: String = name
+    }
+    Console.println(s"Committing $msg")
+    msg
+  }
+
+  override def abort(): Unit = { }
+
+  override def close(): Unit = { }
+}

src/main/scala/uk/co/gresearch/spark/dgraph/connector/TripleDataWriterFactory.scala

@@ -0,0 +1,10 @@
+package uk.co.gresearch.spark.dgraph.connector
+
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.connector.write.{DataWriter, DataWriterFactory}
+import org.apache.spark.sql.types.StructType
+import uk.co.gresearch.spark.dgraph.connector.model.GraphTableModel
+
+case class TripleDataWriterFactory(schema: StructType, model: GraphTableModel) extends DataWriterFactory {
+  override def createWriter(partitionId: Int, taskId: Long): DataWriter[InternalRow] = TripleDataWriter(schema, model)
+}

src/main/scala/uk/co/gresearch/spark/dgraph/connector/TripleTable.scala

@@ -16,19 +16,31 @@
 
 package uk.co.gresearch.spark.dgraph.connector
 
-import java.util.UUID
-
+import org.apache.spark.sql.connector.catalog.{SupportsWrite, TableCapability}
 import org.apache.spark.sql.connector.read.ScanBuilder
+import org.apache.spark.sql.connector.write.{LogicalWriteInfo, WriteBuilder}
 import org.apache.spark.sql.types.StructType
 import org.apache.spark.sql.util.CaseInsensitiveStringMap
 import uk.co.gresearch.spark.dgraph.connector.model.GraphTableModel
 import uk.co.gresearch.spark.dgraph.connector.partitioner.Partitioner
 
-case class TripleTable(partitioner: Partitioner, model: GraphTableModel, val cid: UUID) extends TableBase {
+import java.util
+import java.util.UUID
+import scala.jdk.CollectionConverters._
+
+case class TripleTable(partitioner: Partitioner, model: GraphTableModel, cid: UUID)
+  extends TableBase with SupportsWrite {
 
   override def schema(): StructType = model.schema()
 
   override def newScanBuilder(options: CaseInsensitiveStringMap): ScanBuilder =
     TripleScanBuilder(partitioner, model)
 
+  override def newWriteBuilder(logicalWriteInfo: LogicalWriteInfo): WriteBuilder =
+    TripleWriteBuilder(logicalWriteInfo.schema(), model)
+
+  override def capabilities(): util.Set[TableCapability] = Set(
+    TableCapability.BATCH_READ, TableCapability.BATCH_WRITE, TableCapability.ACCEPT_ANY_SCHEMA
+  ).asJava
+
 }

src/main/scala/uk/co/gresearch/spark/dgraph/connector/TripleWriteBuilder.scala

@@ -0,0 +1,10 @@
+package uk.co.gresearch.spark.dgraph.connector
+
+import org.apache.spark.sql.connector.write.{BatchWrite, WriteBuilder}
+import org.apache.spark.sql.types.StructType
+import uk.co.gresearch.spark.dgraph.connector.model.GraphTableModel
+
+case class TripleWriteBuilder(schema: StructType, model: GraphTableModel)
+  extends WriteBuilder {
+  override def buildForBatch(): BatchWrite = TripleBatchWrite(schema, model)
+}

src/main/scala/uk/co/gresearch/spark/dgraph/connector/sources/NodeSource.scala

@@ -16,8 +16,10 @@
 
 package uk.co.gresearch.spark.dgraph.connector.sources
 
+import org.apache.spark.sql.{DataFrame, SQLContext, SaveMode}
 import org.apache.spark.sql.connector.catalog.Table
 import org.apache.spark.sql.connector.expressions.Transform
+import org.apache.spark.sql.sources.{BaseRelation, CreatableRelationProvider}
 import org.apache.spark.sql.types.StructType
 import org.apache.spark.sql.util.CaseInsensitiveStringMap
 import uk.co.gresearch.spark.dgraph.connector._
@@ -99,4 +101,11 @@ class NodeSource() extends TableProviderBase
     TripleTable(partitioner, model, clusterState.cid)
   }
 
+  def createRelation(context: SQLContext, mode: SaveMode, parameters: Map[String, String], data: DataFrame): BaseRelation = {
+    new BaseRelation {
+      override def sqlContext: SQLContext = context
+      override def schema: StructType = data.schema
+    }
+  }
+
 }

src/test/scala/uk/co/gresearch/spark/dgraph/connector/TestWriter.scala

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2020 G-Research
+ *
+ * Licensed 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 uk.co.gresearch.spark.dgraph.connector
+
+import org.apache.spark.sql.SaveMode
+import org.apache.spark.sql.types.{DoubleType, StringType}
+import org.scalatest.funspec.AnyFunSpec
+import uk.co.gresearch.spark.dgraph.DgraphTestCluster
+
+class TestWriter extends AnyFunSpec with ConnectorSparkTestSession with DgraphTestCluster {
+
+  import spark.implicits._
+
+  // we want a fresh cluster that we can mutate, definitively not one that is always running and used by all tests
+  override val clusterAlwaysStartUp: Boolean = true
+
+  describe("Connector") {
+    it("should write") {
+      spark.range(0, 1000000, 1, 10)
+        .select(
+          $"id".as("subject"),
+          $"id".cast(StringType).as("str"),
+          $"id".cast(DoubleType).as("dbl")
+        )
+        .repartition($"subject")
+        .sortWithinPartitions($"subject")
+        .write
+        .mode(SaveMode.Append)
+        .option("dgraph.nodes.mode", "wide")
+        .format("uk.co.gresearch.spark.dgraph.nodes")
+        .save(dgraph.target)
+    }
+  }
+}