/*
 * 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.plans

import org.apache.spark.sql.catalyst.expressions.AttributeSet

/**
 * A trait that overrides `references` using children output.
 *
 * It's unnecessary to rewrite attributes for `ReferenceAllColumns` since all of references
 * come from it's children.
 *
 * Note, the only used place is at [[QueryPlan.transformUpWithNewOutput]].
 */
trait ReferenceAllColumns[PlanType <: QueryPlan[PlanType]] { self: QueryPlan[PlanType] =>

  @transient
  override final lazy val references: AttributeSet = AttributeSet(children.flatMap(_.outputSet))
}
