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From viirya <...@git.apache.org>
Subject [GitHub] spark pull request #16578: [SPARK-4502][SQL] Parquet nested column pruning
Date Thu, 02 Nov 2017 06:19:16 GMT
Github user viirya commented on a diff in the pull request:

    https://github.com/apache/spark/pull/16578#discussion_r148437575
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/AggregateFieldExtractionPushdown.scala
---
    @@ -0,0 +1,77 @@
    +/*
    + * 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.catalyst.optimizer
    +
    +import org.apache.spark.sql.catalyst.expressions.{Attribute, AttributeSet, NamedExpression}
    +import org.apache.spark.sql.catalyst.plans.logical.{Aggregate, LogicalPlan, Project}
    +
    +/**
    + * Pushes down aliases to [[expressions.GetStructField]] expressions in an aggregate's
grouping and
    + * aggregate expressions into a projection over its children. The original
    + * [[expressions.GetStructField]] expressions are replaced with references to the pushed
down
    + * aliases.
    + */
    +object AggregateFieldExtractionPushdown extends FieldExtractionPushdown {
    +  override def apply(plan: LogicalPlan): LogicalPlan =
    +    plan transformDown {
    +      case agg @ Aggregate(groupingExpressions, aggregateExpressions, child) =>
    +        val expressions = groupingExpressions ++ aggregateExpressions
    +        val attributes = AttributeSet(expressions.collect { case att: Attribute =>
att })
    +        val childAttributes = AttributeSet(child.expressions)
    +        val fieldExtractors0 =
    +          expressions
    +            .flatMap(getFieldExtractors)
    +            .distinct
    +        val fieldExtractors1 =
    +          fieldExtractors0
    +            .filter(_.collectFirst { case att: Attribute => att }
    +              .filter(attributes.contains).isEmpty)
    +        val fieldExtractors =
    +          fieldExtractors1
    +            .filter(_.collectFirst { case att: Attribute => att }
    +              .filter(childAttributes.contains).nonEmpty)
    +
    +        if (fieldExtractors.nonEmpty) {
    +          val (aliases, substituteAttributes) = constructAliasesAndSubstitutions(fieldExtractors)
    --- End diff --
    
    
    
    We can return original plan if aliases is empty.



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