[SPARK-23303][SQL] improve the explain result for data source v2 relations

external/kafka-0-10-sql/src/test/scala/org/apache/spark/sql/kafka010/KafkaContinuousSourceSuite.scala

@@ -17,20 +17,9 @@
 
 package org.apache.spark.sql.kafka010
 
-import java.util.Properties
-import java.util.concurrent.atomic.AtomicInteger
-
-import org.scalatest.time.SpanSugar._
-import scala.collection.mutable
-import scala.util.Random
-
-import org.apache.spark.SparkContext
-import org.apache.spark.sql.{DataFrame, Dataset, ForeachWriter, Row}
+import org.apache.spark.sql.Dataset
 import org.apache.spark.sql.execution.datasources.v2.DataSourceV2Relation
-import org.apache.spark.sql.execution.streaming.StreamExecution
-import org.apache.spark.sql.execution.streaming.continuous.ContinuousExecution
-import org.apache.spark.sql.streaming.{StreamTest, Trigger}
-import org.apache.spark.sql.test.{SharedSQLContext, TestSparkSession}
+import org.apache.spark.sql.streaming.Trigger
 
 // Run tests in KafkaSourceSuiteBase in continuous execution mode.
 class KafkaContinuousSourceSuite extends KafkaSourceSuiteBase with KafkaContinuousTest
@@ -71,7 +60,8 @@ class KafkaContinuousSourceTopicDeletionSuite extends KafkaContinuousTest {
         eventually(timeout(streamingTimeout)) {
           assert(
             query.lastExecution.logical.collectFirst {
-              case DataSourceV2Relation(_, r: KafkaContinuousReader) => r
+              case r: DataSourceV2Relation if r.reader.isInstanceOf[KafkaContinuousReader] =>
+                r.reader.asInstanceOf[KafkaContinuousReader]
             }.exists { r =>
               // Ensure the new topic is present and the old topic is gone.
               r.knownPartitions.exists(_.topic == topic2)

external/kafka-0-10-sql/src/test/scala/org/apache/spark/sql/kafka010/KafkaContinuousTest.scala

@@ -47,7 +47,8 @@ trait KafkaContinuousTest extends KafkaSourceTest {
     eventually(timeout(streamingTimeout)) {
       assert(
         query.lastExecution.logical.collectFirst {
-          case DataSourceV2Relation(_, r: KafkaContinuousReader) => r
+          case r: DataSourceV2Relation if r.reader.isInstanceOf[KafkaContinuousReader] =>
+            r.reader.asInstanceOf[KafkaContinuousReader]
         }.exists(_.knownPartitions.size == newCount),
         s"query never reconfigured to $newCount partitions")
     }

external/kafka-0-10-sql/src/test/scala/org/apache/spark/sql/kafka010/KafkaSourceSuite.scala

@@ -117,7 +117,8 @@ abstract class KafkaSourceTest extends StreamTest with SharedSQLContext {
       } ++ (query.get.lastExecution match {
         case null => Seq()
         case e => e.logical.collect {
-          case DataSourceV2Relation(_, reader: KafkaContinuousReader) => reader
+          case r: DataSourceV2Relation if r.reader.isInstanceOf[KafkaContinuousReader] =>
+            r.reader.asInstanceOf[KafkaContinuousReader]
         }
       })
       if (sources.isEmpty) {

sql/core/src/main/scala/org/apache/spark/sql/DataFrameReader.scala

@@ -189,11 +189,9 @@ class DataFrameReader private[sql](sparkSession: SparkSession) extends Logging {
 
     val cls = DataSource.lookupDataSource(source, sparkSession.sessionState.conf)
     if (classOf[DataSourceV2].isAssignableFrom(cls)) {
-      val ds = cls.newInstance()
+      val ds = cls.newInstance().asInstanceOf[DataSourceV2]
       val options = new DataSourceOptions((extraOptions ++
-        DataSourceV2Utils.extractSessionConfigs(
-          ds = ds.asInstanceOf[DataSourceV2],
-          conf = sparkSession.sessionState.conf)).asJava)
+        DataSourceV2Utils.extractSessionConfigs(ds, sparkSession.sessionState.conf)).asJava)
 
       // Streaming also uses the data source V2 API. So it may be that the data source implements
       // v2, but has no v2 implementation for batch reads. In that case, we fall back to loading
@@ -221,7 +219,7 @@ class DataFrameReader private[sql](sparkSession: SparkSession) extends Logging {
       if (reader == null) {
         loadV1Source(paths: _*)
       } else {
-        Dataset.ofRows(sparkSession, DataSourceV2Relation(reader))
+        Dataset.ofRows(sparkSession, DataSourceV2Relation(ds, reader))
       }
     } else {
       loadV1Source(paths: _*)

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/DataSourceV2QueryPlan.scala

@@ -0,0 +1,96 @@
+/*
+ * 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.datasources.v2
+
+import java.util.Objects
+
+import org.apache.commons.lang3.StringUtils
+
+import org.apache.spark.sql.catalyst.expressions.Attribute
+import org.apache.spark.sql.internal.SQLConf
+import org.apache.spark.sql.sources.v2.DataSourceV2
+import org.apache.spark.sql.sources.v2.reader._
+import org.apache.spark.util.Utils
+
+/**
+ * A base class for data source v2 related query plan(both logical and physical). It defines the
+ * equals/hashCode methods, and provides a string representation of the query plan, according to
+ * some common information.
+ */
+trait DataSourceV2QueryPlan {
+
+  /**
+   * The output of the data source reader, w.r.t. column pruning.
+   */
+  def output: Seq[Attribute]
+
+  /**
+   * The instance of this data source implementation. Note that we only consider its class in
+   * equals/hashCode, not the instance itself.
+   */
+  def source: DataSourceV2
+
+  /**
+   * The created data source reader. Here we use it to get the filters that has been pushed down
+   * so far, itself doesn't take part in the equals/hashCode.
+   */
+  def reader: DataSourceReader
+
+  private lazy val filters = reader match {
+    case s: SupportsPushDownCatalystFilters => s.pushedCatalystFilters().toSet
+    case s: SupportsPushDownFilters => s.pushedFilters().toSet
+    case _ => Set.empty
+  }
+
+  /**
+   * The metadata of this data source query plan that can be used for equality check.
+   */
+  private def metadata: Seq[Any] = Seq(output, source.getClass, filters)
+
+  def canEqual(other: Any): Boolean
+
+  override def equals(other: Any): Boolean = other match {
+    case other: DataSourceV2QueryPlan => canEqual(other) && metadata == other.metadata
+    case _ => false
+  }
+
+  override def hashCode(): Int = {
+    metadata.map(Objects.hashCode).foldLeft(0)((a, b) => 31 * a + b)
+  }
+
+  def metadataString: String = {
+    val entries = scala.collection.mutable.ArrayBuffer.empty[(String, String)]
+    if (filters.nonEmpty) entries += "PushedFilter" -> filters.mkString("[", ", ", "]")
+
+    val outputStr = Utils.truncatedString(output, "[", ", ", "]")
+
+    val entriesStr = if (entries.nonEmpty) {
+      Utils.truncatedString(entries.map {
+        case (key, value) => key + ": " + StringUtils.abbreviate(redact(value), 100)
+      }, " (", ", ", ")")
+    } else {
+      ""
+    }
+
+    s"${source.getClass.getSimpleName}$outputStr$entriesStr"
+  }
+
+  private def redact(text: String): String = {
+    Utils.redact(SQLConf.get.stringRedationPattern, text)
+  }
+}

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/DataSourceV2Relation.scala

@@ -20,15 +20,23 @@ package org.apache.spark.sql.execution.datasources.v2
 import org.apache.spark.sql.catalyst.analysis.MultiInstanceRelation
 import org.apache.spark.sql.catalyst.expressions.AttributeReference
 import org.apache.spark.sql.catalyst.plans.logical.{LeafNode, Statistics}
+import org.apache.spark.sql.sources.v2.DataSourceV2
 import org.apache.spark.sql.sources.v2.reader._
 
 case class DataSourceV2Relation(
     output: Seq[AttributeReference],
-    reader: DataSourceReader)
-  extends LeafNode with MultiInstanceRelation with DataSourceReaderHolder {
+    source: DataSourceV2,
+    reader: DataSourceReader,
+    override val isStreaming: Boolean)
+  extends LeafNode with MultiInstanceRelation with DataSourceV2QueryPlan {
 
   override def canEqual(other: Any): Boolean = other.isInstanceOf[DataSourceV2Relation]
 
+  override def simpleString: String = {
+    val streamingHeader = if (isStreaming) "Streaming " else ""
+    s"${streamingHeader}Relation $metadataString"
+  }
+
   override def computeStats(): Statistics = reader match {
     case r: SupportsReportStatistics =>
       Statistics(sizeInBytes = r.getStatistics.sizeInBytes().orElse(conf.defaultSizeInBytes))
@@ -41,18 +49,8 @@ case class DataSourceV2Relation(
   }
 }
 
-/**
- * A specialization of DataSourceV2Relation with the streaming bit set to true. Otherwise identical
- * to the non-streaming relation.
- */
-class StreamingDataSourceV2Relation(
-    output: Seq[AttributeReference],
-    reader: DataSourceReader) extends DataSourceV2Relation(output, reader) {
-  override def isStreaming: Boolean = true
-}
-
 object DataSourceV2Relation {
-  def apply(reader: DataSourceReader): DataSourceV2Relation = {
-    new DataSourceV2Relation(reader.readSchema().toAttributes, reader)
+  def apply(source: DataSourceV2, reader: DataSourceReader): DataSourceV2Relation = {
+    new DataSourceV2Relation(reader.readSchema().toAttributes, source, reader, isStreaming = false)
   }
 }

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/DataSourceV2ScanExec.scala

@@ -27,6 +27,7 @@ import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.physical
 import org.apache.spark.sql.execution.{ColumnarBatchScan, LeafExecNode, WholeStageCodegenExec}
 import org.apache.spark.sql.execution.streaming.continuous._
+import org.apache.spark.sql.sources.v2.DataSourceV2
 import org.apache.spark.sql.sources.v2.reader._
 import org.apache.spark.sql.sources.v2.reader.streaming.ContinuousReader
 import org.apache.spark.sql.types.StructType
@@ -36,11 +37,14 @@ import org.apache.spark.sql.types.StructType
  */
 case class DataSourceV2ScanExec(
     output: Seq[AttributeReference],
+    @transient source: DataSourceV2,
     @transient reader: DataSourceReader)
-  extends LeafExecNode with DataSourceReaderHolder with ColumnarBatchScan {
+  extends LeafExecNode with DataSourceV2QueryPlan with ColumnarBatchScan {
 
   override def canEqual(other: Any): Boolean = other.isInstanceOf[DataSourceV2ScanExec]
 
+  override def simpleString: String = s"Scan $metadataString"
+
   override def outputPartitioning: physical.Partitioning = reader match {
     case s: SupportsReportPartitioning =>
       new DataSourcePartitioning(

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/DataSourceV2Strategy.scala

@@ -23,8 +23,8 @@ import org.apache.spark.sql.execution.SparkPlan
 
 object DataSourceV2Strategy extends Strategy {
   override def apply(plan: LogicalPlan): Seq[SparkPlan] = plan match {
-    case DataSourceV2Relation(output, reader) =>
-      DataSourceV2ScanExec(output, reader) :: Nil
+    case r: DataSourceV2Relation =>
+      DataSourceV2ScanExec(r.output, r.source, r.reader) :: Nil
 
     case WriteToDataSourceV2(writer, query) =>
       WriteToDataSourceV2Exec(writer, planLater(query)) :: Nil

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/PushDownOperatorsToDataSource.scala

@@ -39,11 +39,11 @@ object PushDownOperatorsToDataSource extends Rule[LogicalPlan] with PredicateHel
     // TODO: Ideally column pruning should be implemented via a plan property that is propagated
     // top-down, then we can simplify the logic here and only collect target operators.
     val filterPushed = plan transformUp {
-      case FilterAndProject(fields, condition, r @ DataSourceV2Relation(_, reader)) =>
+      case FilterAndProject(fields, condition, r: DataSourceV2Relation) =>
         val (candidates, nonDeterministic) =
           splitConjunctivePredicates(condition).partition(_.deterministic)
 
-        val stayUpFilters: Seq[Expression] = reader match {
+        val stayUpFilters: Seq[Expression] = r.reader match {
           case r: SupportsPushDownCatalystFilters =>
             r.pushCatalystFilters(candidates.toArray)
 

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

@@ -27,9 +27,9 @@ import org.apache.spark.sql.catalyst.encoders.RowEncoder
 import org.apache.spark.sql.catalyst.expressions.{Attribute, AttributeMap, CurrentBatchTimestamp, CurrentDate, CurrentTimestamp}
 import org.apache.spark.sql.catalyst.plans.logical.{LocalRelation, LogicalPlan}
 import org.apache.spark.sql.execution.SQLExecution
-import org.apache.spark.sql.execution.datasources.v2.{StreamingDataSourceV2Relation, WriteToDataSourceV2}
+import org.apache.spark.sql.execution.datasources.v2.{DataSourceV2Relation, WriteToDataSourceV2}
 import org.apache.spark.sql.execution.streaming.sources.{InternalRowMicroBatchWriter, MicroBatchWriter}
-import org.apache.spark.sql.sources.v2.{DataSourceOptions, MicroBatchReadSupport, StreamWriteSupport}
+import org.apache.spark.sql.sources.v2.{DataSourceOptions, DataSourceV2, MicroBatchReadSupport, StreamWriteSupport}
 import org.apache.spark.sql.sources.v2.reader.streaming.{MicroBatchReader, Offset => OffsetV2}
 import org.apache.spark.sql.sources.v2.writer.SupportsWriteInternalRow
 import org.apache.spark.sql.streaming.{OutputMode, ProcessingTime, Trigger}
@@ -52,6 +52,8 @@ class MicroBatchExecution(
 
   @volatile protected var sources: Seq[BaseStreamingSource] = Seq.empty
 
+  private val readerToDataSourceMap = MutableMap.empty[MicroBatchReader, DataSourceV2]
+
   private val triggerExecutor = trigger match {
     case t: ProcessingTime => ProcessingTimeExecutor(t, triggerClock)
     case OneTimeTrigger => OneTimeExecutor()
@@ -90,6 +92,7 @@ class MicroBatchExecution(
             metadataPath,
             new DataSourceOptions(options.asJava))
           nextSourceId += 1
+          readerToDataSourceMap(reader) = source
           StreamingExecutionRelation(reader, output)(sparkSession)
         })
       case s @ StreamingRelationV2(_, sourceName, _, output, v1Relation) =>
@@ -405,12 +408,15 @@ class MicroBatchExecution(
             case v1: SerializedOffset => reader.deserializeOffset(v1.json)
             case v2: OffsetV2 => v2
           }
-          reader.setOffsetRange(
-            toJava(current),
-            Optional.of(availableV2))
+          reader.setOffsetRange(toJava(current), Optional.of(availableV2))
           logDebug(s"Retrieving data from $reader: $current -> $availableV2")
-          Some(reader ->
-            new StreamingDataSourceV2Relation(reader.readSchema().toAttributes, reader))
+          Some(reader -> new DataSourceV2Relation(
+            reader.readSchema().toAttributes,
+            // Provide a fake value here just in case something went wrong, e.g. the reader gives
+            // a wrong `equals` implementation.
+            readerToDataSourceMap.getOrElse(reader, FakeDataSourceV2),
+            reader,
+            isStreaming = true))
         case _ => None
       }
     }
@@ -500,3 +506,5 @@ class MicroBatchExecution(
     Optional.ofNullable(scalaOption.orNull)
   }
 }
+
+object FakeDataSourceV2 extends DataSourceV2