Re: [PR] [SPARK-47167][SQL] Add concrete class for JDBC anonymous relation [spark]

["MaxGekk (via GitHub)" <gi...@apache.org>]

MaxGekk commented on code in PR #45259:
URL: https://github.com/apache/spark/pull/45259#discussion_r1506445746


##########
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/jdbc/JDBCV1CompatibleRelation.scala:
##########
@@ -0,0 +1,57 @@
+/*
+ * 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.jdbc
+
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql.{Row, SQLContext}
+import org.apache.spark.sql.connector.expressions.filter.Predicate
+import org.apache.spark.sql.execution.datasources.jdbc.JDBCRelation
+import org.apache.spark.sql.execution.datasources.v2.TableSampleInfo
+import org.apache.spark.sql.sources.{BaseRelation, TableScan}
+import org.apache.spark.sql.types.StructType
+
+/**
+ * Relation that is compatible with V1 TableScan,
+ * but it uses JDBCRelation's buildScan which accepts all v2 pushdowns
+ */
+case class JDBCV1CompatibleRelation(
+    context: SQLContext,
+    prunedSchema: StructType,
+    relation: JDBCRelation,
+    pushedPredicates: Array[Predicate],
+    pushedAggregateColumn: Array[String] = Array(),
+    groupByColumns: Option[Array[String]],
+    tableSample: Option[TableSampleInfo],
+    pushedLimit: Int,
+    sortOrders: Array[String],
+    pushedOffset: Int) extends BaseRelation with TableScan {
+  override def sqlContext: SQLContext = context
+  override def schema: StructType = prunedSchema
+  override def needConversion: Boolean = relation.needConversion
+  override def buildScan(): RDD[Row] = {
+    val columnList = if (groupByColumns.isEmpty) {
+      prunedSchema.map(_.name).toArray
+    } else {
+      pushedAggregateColumn
+    }
+
+    relation.buildScan(columnList, prunedSchema, pushedPredicates, groupByColumns, tableSample,
+      pushedLimit, sortOrders, pushedOffset)
+  }
+
+  override def toString: String = "JDBC Relation"

Review Comment:
   This one is confusing slightly. How should an user distinguish it from `JDBCRelation` which outputs `JDBCRelation ...`? 



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