[GitHub] [spark] rdblue commented on a change in pull request #25955: [SPARK-29277][SQL] Add early DSv2 filter and projection pushdown (WIP)

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rdblue commented on a change in pull request #25955: [SPARK-29277][SQL] Add early DSv2 filter and projection pushdown (WIP)
URL: https://github.com/apache/spark/pull/25955#discussion_r331295860
 
 

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 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/V2ScanRelationPushDown.scala
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+/*
+ * 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 org.apache.spark.sql.catalyst.expressions.{And, SubqueryExpression}
+import org.apache.spark.sql.catalyst.planning.PhysicalOperation
+import org.apache.spark.sql.catalyst.plans.logical.{Filter, LogicalPlan, Project}
+import org.apache.spark.sql.catalyst.rules.Rule
+import org.apache.spark.sql.execution.datasources.DataSourceStrategy
+
+object V2ScanRelationPushDown extends Rule[LogicalPlan] {
+  override def apply(plan: LogicalPlan): LogicalPlan = plan transformDown {
+    case PhysicalOperation(project, filters, relation: DataSourceV2Relation) =>
+      val scanBuilder = relation.newScanBuilder()
+
+      val (withSubquery, withoutSubquery) = filters.partition(SubqueryExpression.hasSubquery)
+      val normalizedFilters = DataSourceStrategy.normalizeFilters(
+        withoutSubquery, relation.output)
+
+      // `pushedFilters` will be pushed down and evaluated in the underlying data sources.
+      // `postScanFilters` need to be evaluated after the scan.
+      // `postScanFilters` and `pushedFilters` can overlap, e.g. the parquet row group filter.
+      val (pushedFilters, postScanFiltersWithoutSubquery) =
+      PushDownUtils.pushFilters(scanBuilder, normalizedFilters)
+      val postScanFilters = postScanFiltersWithoutSubquery ++ withSubquery
+      val (scan, output) = PushDownUtils.pruneColumns(
+        scanBuilder, relation, project ++ postScanFilters)
+      logInfo(
+        s"""
+           |Pushing operators to ${relation.name}
+           |Pushed Filters: ${pushedFilters.mkString(", ")}
+           |Post-Scan Filters: ${postScanFilters.mkString(",")}
+           |Output: ${output.mkString(", ")}
+         """.stripMargin)
+
+      val scanRelation = DataSourceV2ScanRelation(relation.table, scan, output)
 
 Review comment:
   I implemented this, but I didn't push it because it would cause test failures when `computeStats` is called on the `DataSourceV2Relation`.
   
   But, that raises another problem with not converting to a scan relation. If stats are used in the optimizer, we have to convert to scan relation to avoid planning the query splits twice. Otherwise, a scan is built for `computeStats` and then another scan is built when converting to the physical plan. Both may have to plan splits. So I think I'll leave this as it is to catch as many cases as possible.

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