[GitHub] spark pull request #16578: [SPARK-4502][SQL] Parquet nested column pruning

[viirya <gi...@git.apache.org>]

Github user viirya commented on a diff in the pull request:

    https://github.com/apache/spark/pull/16578#discussion_r148446396
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/JoinFieldExtractionPushdown.scala ---
    @@ -0,0 +1,66 @@
    +/*
    + * 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.planning.PhysicalOperation
    +import org.apache.spark.sql.catalyst.plans.logical.{Join, LogicalPlan, Project}
    +
    +/**
    + * Pushes down aliases to [[expressions.GetStructField]] expressions in a projection over a join
    + * and its join condition. The original [[expressions.GetStructField]] expressions are replaced
    + * with references to the pushed down aliases.
    + */
    +object JoinFieldExtractionPushdown extends FieldExtractionPushdown {
    --- End diff --
    
    Oh, I just meant we may skip most of the rule if it can't be applied. Please see my comment below.


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