gianm commented on a change in pull request #9111: Add HashJoinSegment, a virtual segment for joins. URL: https://github.com/apache/druid/pull/9111#discussion_r367607423
########## File path: processing/src/main/java/org/apache/druid/segment/join/JoinableClause.java ########## @@ -0,0 +1,145 @@ +/* + * 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.join; + +import com.google.common.base.Preconditions; +import org.apache.druid.java.util.common.IAE; + +import javax.annotation.Nullable; +import java.util.List; +import java.util.Objects; +import java.util.stream.Collectors; + +/** + * Represents everything about a join clause except for the left-hand datasource. In other words, if the full join + * clause is "t1 JOIN t2 ON t1.x = t2.x" then this class represents "JOIN t2 ON x = t2.x" -- it does not include + * references to the left-hand "t1". + */ +public class JoinableClause +{ + private final String prefix; Review comment: I'm planning to add this javadoc, which'll make it clearer: ```java /** * The prefix to apply to all columns from the Joinable. The idea is that during a join, any columns that start with * this prefix should be retrieved from our Joinable's {@link JoinMatcher#getColumnSelectorFactory()}. Any other * columns should be returned from the left-hand side of the join. * * The prefix can be any string, as long as it is nonempty and not itself a prefix of the reserved column name * {@code __time}. * * @see #getAvailableColumnsPrefixed() the list of columns from our {@link Joinable} with prefixes attached * @see #unprefix a method for removing prefixes */ ``` ---------------------------------------------------------------- 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 With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@druid.apache.org For additional commands, e-mail: commits-h...@druid.apache.org
