Github user HyukjinKwon commented on a diff in the pull request: https://github.com/apache/spark/pull/21889#discussion_r209528183 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetSchemaPruning.scala --- @@ -0,0 +1,200 @@ +/* + * 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.parquet + +import org.apache.spark.sql.catalyst.expressions.{And, Attribute, Expression, NamedExpression} +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.{ProjectionOverSchema, SelectedField} +import org.apache.spark.sql.execution.datasources.{HadoopFsRelation, LogicalRelation} +import org.apache.spark.sql.internal.SQLConf +import org.apache.spark.sql.types.{ArrayType, DataType, MapType, StructField, StructType} + +/** + * Prunes unnecessary Parquet columns given a [[PhysicalOperation]] over a + * [[ParquetRelation]]. By "Parquet column", we mean a column as defined in the + * Parquet format. In Spark SQL, a root-level Parquet column corresponds to a + * SQL column, and a nested Parquet column corresponds to a [[StructField]]. + */ +private[sql] object ParquetSchemaPruning extends Rule[LogicalPlan] { + override def apply(plan: LogicalPlan): LogicalPlan = + if (SQLConf.get.nestedSchemaPruningEnabled) { + apply0(plan) + } else { + plan + } + + private def apply0(plan: LogicalPlan): LogicalPlan = + plan transformDown { + case op @ PhysicalOperation(projects, filters, + l @ LogicalRelation(hadoopFsRelation @ HadoopFsRelation(_, _, + dataSchema, _, _: ParquetFileFormat, _), _, _, _)) => + val projectionRootFields = projects.flatMap(getRootFields) + val filterRootFields = filters.flatMap(getRootFields) + val requestedRootFields = (projectionRootFields ++ filterRootFields).distinct + + // If requestedRootFields includes a nested field, continue. Otherwise, + // return op + if (requestedRootFields.exists { case RootField(_, derivedFromAtt) => !derivedFromAtt }) { --- End diff -- Are we really unable to make some private functions and split some logics at least?
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