gustavodemorais commented on code in PR #27733: URL: https://github.com/apache/flink/pull/27733#discussion_r2885015444
########## flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/rules/logical/SimplifyCoalesceWithEquiJoinConditionRule.java: ########## @@ -0,0 +1,302 @@ +/* + * 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.flink.table.planner.plan.rules.logical; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.table.functions.BuiltInFunctionDefinitions; +import org.apache.flink.table.planner.functions.bridging.BridgingSqlFunction; +import org.apache.flink.table.planner.plan.utils.FlinkRexUtil; + +import org.apache.calcite.plan.RelOptRuleCall; +import org.apache.calcite.plan.RelRule; +import org.apache.calcite.rel.RelNode; +import org.apache.calcite.rel.core.Calc; +import org.apache.calcite.rel.core.Join; +import org.apache.calcite.rel.core.JoinInfo; +import org.apache.calcite.rel.core.JoinRelType; +import org.apache.calcite.rel.core.Project; +import org.apache.calcite.rex.RexBuilder; +import org.apache.calcite.rex.RexCall; +import org.apache.calcite.rex.RexInputRef; +import org.apache.calcite.rex.RexNode; +import org.apache.calcite.rex.RexShuttle; +import org.apache.calcite.sql.SqlKind; +import org.apache.calcite.sql.SqlOperator; +import org.apache.calcite.util.mapping.IntPair; +import org.immutables.value.Value; + +import java.util.function.Predicate; + +/** + * Simplifies {@code COALESCE(b.k, a.k)} to the preserved-side column reference when the two + * arguments reference columns from opposite sides of an equi-join condition. + * + * <p>For a {@code LEFT JOIN a ON a.k = b.k}, {@code COALESCE(b.k, a.k)} always equals {@code a.k}: + * + * <ul> + * <li>When b matches: {@code b.k = a.k} (equi-join guarantees this), so the result is {@code + * a.k}. + * <li>When b doesn't match: {@code b.k} is NULL, so the result falls through to {@code a.k}. + * </ul> + * + * <p>Both orderings ({@code COALESCE(b.k, a.k)} and {@code COALESCE(a.k, b.k)}) resolve to the + * preserved-side key. This applies to LEFT, RIGHT, and INNER joins. FULL OUTER joins are not + * handled because both sides can generate nulls. + * + * <p>This rule matches a {@link Project} or {@link Calc} whose input is a {@link Join}. It uses a + * {@link RexShuttle} to recursively find and simplify applicable COALESCE calls, including those + * nested inside other expressions (e.g., {@code CAST(COALESCE(b.k, a.k) AS VARCHAR)}). + */ +@Internal [email protected] +public class SimplifyCoalesceWithEquiJoinConditionRule Review Comment: I think having different rules is cleaner since they work differently: 1. RemoveUnreachableCoalesceArgumentsRule trims arguments based on type nullability metadata (e.g., COALESCE(nonNull, x) -> nonNull), without any join awareness. 2. This one is specific to joins and merging both would look less elegant IMO. -- 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]
