wangshuo128 commented on code in PR #10890: URL: https://github.com/apache/doris/pull/10890#discussion_r924092890
########## fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/logical/ReorderJoin.java: ########## @@ -0,0 +1,215 @@ +// 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.doris.nereids.rules.rewrite.logical; + +import org.apache.doris.nereids.rules.Rule; +import org.apache.doris.nereids.rules.RuleType; +import org.apache.doris.nereids.rules.rewrite.OneRewriteRuleFactory; +import org.apache.doris.nereids.trees.expressions.EqualTo; +import org.apache.doris.nereids.trees.expressions.Expression; +import org.apache.doris.nereids.trees.expressions.Slot; +import org.apache.doris.nereids.trees.expressions.visitor.SlotExtractor; +import org.apache.doris.nereids.trees.plans.JoinType; +import org.apache.doris.nereids.trees.plans.Plan; +import org.apache.doris.nereids.trees.plans.logical.LogicalFilter; +import org.apache.doris.nereids.trees.plans.logical.LogicalJoin; +import org.apache.doris.nereids.trees.plans.visitor.PlanVisitor; +import org.apache.doris.nereids.util.ExpressionUtils; + +import java.util.ArrayList; +import java.util.HashSet; +import java.util.List; +import java.util.Map; +import java.util.Optional; +import java.util.Set; +import java.util.stream.Collectors; + +/** + * Try to eliminate cross join via finding join conditions in filters and change the join orders. + * <p> + * <pre> + * For example: + * + * input: + * SELECT * FROM t1, t2, t3 WHERE t1.id=t3.id AND t2.id=t3.id + * + * output: + * SELECT * FROM t1 JOIN t3 ON t1.id=t3.id JOIN t2 ON t2.id=t3.id + * </pre> + * </p> + * TODO: This is tested by SSB queries currently, add more `unit` test for this rule + * when we have a plan building and comparing framework. + */ +public class ReorderJoin extends OneRewriteRuleFactory { + @Override + public Rule<Plan> build() { + return logicalFilter(subTree(LogicalJoin.class, LogicalFilter.class)).then(filter -> { + PlanCollector collector = new PlanCollector(); + filter.accept(collector, null); + List<Plan> joinInputs = collector.joinInputs; + List<Expression> conjuncts = collector.conjuncts; + + if (joinInputs.size() >= 3 && !conjuncts.isEmpty()) { + return reorderJoinsAccordingToConditions(joinInputs, conjuncts); + } else { + return filter; + } + }).toRule(RuleType.REORDER_JOIN); + } + + /** + * Reorder join orders according to join conditions to eliminate cross join. + * <p/> + * Let's say we have input join tables: [t1, t2, t3] and + * conjunctive predicates: [t1.id=t3.id, t2.id=t3.id] + * The input join for t1 and t2 is cross join. + * <p/> + * The algorithm split join inputs into two groups: `left input` t1 and `candidate right input` [t2, t3]. + * Try to find an inner join from t1 and candidate right inputs [t2, t3], if any combination + * of [Join(t1, t2), Join(t1, t3)] could be optimized to inner join according to the join conditions. + * <p/> + * As a result, Join(t1, t3) is an inner join. + * Then the logic is applied to the rest of [Join(t1, t3), t2] recursively. + */ + private Plan reorderJoinsAccordingToConditions(List<Plan> joinInputs, List<Expression> conjuncts) { + if (joinInputs.size() == 2) { + Set<Slot> joinOutput = getJoinOutput(joinInputs.get(0), joinInputs.get(1)); + Map<Boolean, List<Expression>> split = splitConjuncts(conjuncts, joinOutput); + List<Expression> joinConditions = split.get(true); + List<Expression> nonJoinConditions = split.get(false); + + Optional<Expression> cond; + if (joinConditions.isEmpty()) { + cond = Optional.empty(); + } else { + cond = Optional.of(ExpressionUtils.and(joinConditions)); + } + + LogicalJoin join = new LogicalJoin(JoinType.INNER_JOIN, cond, joinInputs.get(0), joinInputs.get(1)); + if (nonJoinConditions.isEmpty()) { + return join; + } else { + return new LogicalFilter(ExpressionUtils.and(nonJoinConditions), join); + } + } else { + Plan left = joinInputs.get(0); + List<Plan> candidate = joinInputs.subList(1, joinInputs.size()); + + List<Slot> leftOutput = left.getOutput(); + Optional<Plan> rightOpt = candidate.stream().filter(right -> { + List<Slot> rightOutput = right.getOutput(); + + Set<Slot> joinOutput = getJoinOutput(left, right); + Optional<Expression> joinCond = conjuncts.stream() + .filter(expr -> { + Set<Slot> exprInputSlots = SlotExtractor.extractSlot(expr); + if (exprInputSlots.isEmpty()) { + return false; + } + + if (new HashSet<>(leftOutput).containsAll(exprInputSlots)) { + return false; + } + + if (new HashSet<>(rightOutput).containsAll(exprInputSlots)) { + return false; + } + + return joinOutput.containsAll(exprInputSlots); + }).findFirst(); + return joinCond.isPresent(); + }).findFirst(); + + Plan right = rightOpt.orElseGet(() -> candidate.get(1)); + Set<Slot> joinOutput = getJoinOutput(left, right); + Map<Boolean, List<Expression>> split = splitConjuncts(conjuncts, joinOutput); + List<Expression> joinConditions = split.get(true); + List<Expression> nonJoinConditions = split.get(false); + + Optional<Expression> cond; + if (joinConditions.isEmpty()) { + cond = Optional.empty(); + } else { + cond = Optional.of(ExpressionUtils.and(joinConditions)); + } + + LogicalJoin join = new LogicalJoin(JoinType.INNER_JOIN, cond, left, right); + + List<Plan> newInputs = new ArrayList<>(); + newInputs.add(join); + newInputs.addAll(candidate.stream().filter(plan -> !right.equals(plan)).collect(Collectors.toList())); + return reorderJoinsAccordingToConditions(newInputs, nonJoinConditions); + } + } + + private Set<Slot> getJoinOutput(Plan left, Plan right) { + HashSet<Slot> joinOutput = new HashSet<>(); + joinOutput.addAll(left.getOutput()); + joinOutput.addAll(right.getOutput()); + return joinOutput; + } + + private Map<Boolean, List<Expression>> splitConjuncts(List<Expression> conjuncts, Set<Slot> slots) { Review Comment: I would refactor similar logic when we support a more comprehensive join and filter rewrite. -- This is an automated message from the Apache Git Service. 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