peter-toth commented on a change in pull request #28885: URL: https://github.com/apache/spark/pull/28885#discussion_r460115721
########## File path: sql/catalyst/src/main/scala/org/apache/spark/sql/util/ReuseMap.scala ########## @@ -0,0 +1,72 @@ +/* + * 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.util + +import scala.collection.mutable.{ArrayBuffer, Map} + +import org.apache.spark.sql.catalyst.plans.QueryPlan +import org.apache.spark.sql.types.StructType + +/** + * Map of canonicalized plans that can be used to find reuse possibilities. + * + * To avoid costly canonicalization of a plan: + * - we use its schema first to check if it can be replaced to a reused one at all + * - we insert it into the map of canonicalized plans only when at least 2 have the same schema + * + * @tparam T the type of the node we want to reuse + */ +class ReuseMap[T <: T2, T2 <: QueryPlan[T2]] { Review comment: It might look like `T2` is not required, but it is "silently" used at `sameSchema.find(plan.sameResult)` and Scala would complain without it. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org
