imply-cheddar commented on code in PR #12646: URL: https://github.com/apache/druid/pull/12646#discussion_r899697562
########## processing/src/main/java/org/apache/druid/segment/DeprecatedQueryableIndexColumnSelector.java: ########## @@ -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.druid.segment; + +import org.apache.druid.segment.column.ColumnHolder; + +import javax.annotation.Nullable; +import java.util.List; + +/** + * It likely looks weird that we are creating a new instance of ColumnSelector here that begins its life deprecated + * and only delegates methods to the Queryable Index. This is done intentionally so that the QueryableIndex doesn't + * accidentally get used as a ColumnSelector. + * + * The lifecycle of the QueryableIndex is over the lifetime of the segment on a specific process, while + * the ColumnSelector's lifecycle is for a given query. When we don't use the same ColumnSelector for an + * entire query, we defeat caching and use a lot more resources than necessary for queries. + * + * Places that use this class are intentionally circumventing column caching and column lifecycle management, + * ostensibly because those code locations know that they are only looking at metadata. If a code path uses this + * and actually accesses a column instead of just looking at metadata, it will leak any resources that said column + * requires. + * + * The ColumnCache is the preferred implementation of a ColumnSelector, it takes a Closer and that closer can be used + * to ensure that resources are cleaned up. + */ +@Deprecated +public class DeprecatedQueryableIndexColumnSelector implements ColumnSelector Review Comment: The `AutoStrategy` one could definitely be adjusted, the other places are all significantly larger changes than the words used to describe them. So, while I agree that I wish this didn't exist, the goal of the PR is to get the pool poisoned so that we are sure that future leaks get caught, I don't think we should block that goal on perfection here. -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
