XieJiann commented on code in PR #13902: URL: https://github.com/apache/doris/pull/13902#discussion_r1013581583
########## fe/fe-core/src/main/java/org/apache/doris/nereids/rules/joinreorder/hypergraph/GraphSimplifier.java: ########## @@ -0,0 +1,383 @@ +// 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.joinreorder.hypergraph; + +import org.apache.doris.common.Pair; +import org.apache.doris.nereids.memo.Group; +import org.apache.doris.nereids.memo.GroupExpression; +import org.apache.doris.nereids.properties.PhysicalProperties; +import org.apache.doris.nereids.stats.StatsCalculator; +import org.apache.doris.nereids.trees.plans.GroupPlan; +import org.apache.doris.nereids.trees.plans.Plan; +import org.apache.doris.nereids.trees.plans.logical.LogicalJoin; + +import com.google.common.base.Preconditions; + +import java.util.ArrayList; +import java.util.BitSet; +import java.util.List; +import java.util.Optional; +import java.util.PriorityQueue; + +/** + * GraphSimplifier is used to simplify HyperGraph {@link HyperGraph} + */ +public class GraphSimplifier { + class SimplificationStep { + double benefit; + int beforeIndex; + int afterIndex; + BitSet newLeft; + BitSet newRight; + Plan leftPlan; + Plan rightPlan; + + SimplificationStep(double benefit, int beforeIndex, int afterIndex, Plan leftPlan, Plan rightPlan, + BitSet newLeft, BitSet newRight) { + this.afterIndex = afterIndex; + this.beforeIndex = beforeIndex; + this.benefit = benefit; + this.leftPlan = leftPlan; + this.rightPlan = rightPlan; + this.newLeft = newLeft; + this.newRight = newRight; + } + + public double getBenefit() { + return benefit; + } + } + + class BestSimplification implements Comparable<BestSimplification> { + int bestNeighbor = -1; + Optional<SimplificationStep> step = Optional.empty(); + // This data whether to be added to the queue + boolean isInQueue = false; + + @Override + public int compareTo(GraphSimplifier.BestSimplification o) { + Preconditions.checkArgument(step.isPresent()); + return Double.compare(getBenefit(), o.getBenefit()); + } + + public double getBenefit() { + return step.get().getBenefit(); + } + + public void setStep(SimplificationStep step) { + this.step = Optional.of(step); + } + + public SimplificationStep getStep() { + return step.get(); + } + } + + // The graph we are simplifying + HyperGraph graph; + + // It stores the children plan of one edge. + // we don't store it in hyper graph, because it's just used for simulating join. + // In fact, the graph simplifier just generate the partial order of join operator. + List<Pair<Plan, Plan>> joinPlans = new ArrayList<>(); + + // This is used for cache the intermediate results when calculate the benefit + // Note that we store it for the after. Because if we put B after A (t1 Join_A t2 Join_B t3), + // B is changed. Therefore, Any step that involves B need to be recalculated. + List<BestSimplification> simplifications = new ArrayList<>(); + PriorityQueue<BestSimplification> priorityQueue = new PriorityQueue<>(); + int edgeSize; + + GraphSimplifier(HyperGraph graph) { + this.graph = graph; + edgeSize = graph.edges.size(); + for (int i = 0; i < edgeSize; i++) { + BestSimplification bestSimplification = new BestSimplification(); + Plan leftPlan = graph.getPlan(graph.getEdge(i).getLeft()); + Plan rightPlan = graph.getPlan(graph.getEdge(i).getRight()); + joinPlans.add(Pair.of(leftPlan, rightPlan)); + simplifications.add(bestSimplification); + } + } + + /** + * This function init the first simplification step + */ + public void initFirstStep() { + for (int i = 0; i < edgeSize; i += 2) { + processNeighbors(i, i + 1, edgeSize); + } + } + + /** + * This function will repeatedly apply simplification steps util the number of csg-cmp pair + * is under the limit. + * In hyper graph, counting the csg-cmp pair is more expensive than the apply simplification step, therefore + * we use binary search to find the least step we should apply. + * + * @param limit the limit number of the csg-cmp pair + */ + public boolean simplifyGraph(int limit) { + // Now we only support simplify graph until the hyperGraph only contains one plan + Preconditions.checkArgument(limit == 1); + while (applySimplificationStep()) {} + return true; + } + + /** + * This function apply a simplification step + * + * @return If there is no other steps, return false. + */ + public boolean applySimplificationStep() { + if (priorityQueue.isEmpty()) { + return false; + } + BestSimplification bestSimplification = priorityQueue.poll(); + SimplificationStep bestStep = bestSimplification.step.get(); + // TODO: add circle detector to refuse the edge that can cause a circle + graph.modifyEdge(bestStep.afterIndex, bestStep.newLeft, bestStep.newRight); + proposeJoin(bestStep.afterIndex, bestStep.leftPlan, bestStep.rightPlan); + processNeighbors(bestStep.afterIndex, 0, edgeSize); + return true; + } + + /** + * Process all neighbors and try to make simplification step + * Note that when a given ordering is less advantageous and dropped out, + * we need to call this function recursively to update all relative steps. + * + * @param edgeIndex1 The index of join operator that we need to process its neighbors + * @param beginIndex The beginning index of the processing join operators + * @param endIndex The end index of the processing join operators + */ + private void processNeighbors(int edgeIndex1, int beginIndex, int endIndex) { + // Go through the neighbors with lower index, where the best simplification is stored + // Because the best simplification is stored in the edge with lower index, we need to update it recursively + // when we can't reset that best simplification + for (int edgeIndex2 = beginIndex; edgeIndex2 < Integer.max(endIndex, edgeIndex1); edgeIndex2 += 2) { + BestSimplification bestSimplification = simplifications.get(edgeIndex2); + Optional<SimplificationStep> optionalStep = makeSimplificationStep(edgeIndex1, edgeIndex2); + if (!optionalStep.isPresent()) { + continue; + } + if (!proposeSimplificationStep(optionalStep.get(), bestSimplification, edgeIndex1)) { + // Because edgeIndex2 < edgeIndex1, so the recursion is guaranteed to terminate + processNeighbors(edgeIndex2, 0, edgeSize); + } + } + + // Go through the neighbors with higher index, we only need to recalculate all related steps + for (int edgeIndex2 = Integer.max(beginIndex, edgeIndex1 + 1); edgeIndex2 < endIndex; edgeIndex2 += 2) { + BestSimplification bestSimplification = simplifications.get(edgeIndex1); + bestSimplification.bestNeighbor = -1; + Optional<SimplificationStep> optionalStep = makeSimplificationStep(edgeIndex1, edgeIndex2); + if (!optionalStep.isPresent()) { + continue; + } + proposeSimplificationStep(optionalStep.get(), bestSimplification, edgeIndex2); + } + } + + private boolean proposeSimplificationStep(SimplificationStep step, BestSimplification bestSimplification, + int index) { + if (bestSimplification.bestNeighbor == -1 || bestSimplification.getBenefit() <= step.getBenefit()) { + bestSimplification.bestNeighbor = index; + bestSimplification.setStep(step); + updatePriorityQueue(index); + return true; + } + return false; + } + + private void updatePriorityQueue(int index) { + BestSimplification bestSimplification = simplifications.get(index); + if (!bestSimplification.isInQueue) { + if (bestSimplification.bestNeighbor != -1) { + priorityQueue.add(bestSimplification); + bestSimplification.isInQueue = true; + } + } else { + priorityQueue.remove(bestSimplification); + if (bestSimplification.bestNeighbor == -1) { + bestSimplification.isInQueue = false; + } else { + priorityQueue.add(bestSimplification); + } + } + } + + private Optional<SimplificationStep> makeSimplificationStep(int edgeIndex1, int edgeIndex2) { + Edge edge1 = graph.getEdge(edgeIndex1); + Edge edge2 = graph.getEdge(edgeIndex2); + if (edge1.isBefore(edge2) || edge2.isBefore(edge1)) { + return Optional.empty(); + } + + Plan leftPlan1 = joinPlans.get(edgeIndex1).first; + Plan rightPlan1 = joinPlans.get(edgeIndex1).second; + Plan leftPlan2 = joinPlans.get(edgeIndex1).first; + Plan rightPlan2 = joinPlans.get(edgeIndex1).second; + Edge edge1Before2; + Edge edge2Before1; + List<Plan> commonPlan = new ArrayList<>(); + if (isSubPlan(leftPlan1, edge1.getLeft(), leftPlan2, edge2.getLeft(), commonPlan)) { + // (common Join1 right1) Join2 right2 + edge1Before2 = threeLeftJoin(commonPlan.get(0), edge1, rightPlan1, edge2, rightPlan2); + // (common Join2 right2) Join1 right1 + edge2Before1 = threeLeftJoin(commonPlan.get(0), edge2, rightPlan2, edge1, rightPlan1); + } else if (isSubPlan(leftPlan1, edge1.getLeft(), rightPlan2, edge2.getRight(), commonPlan)) { + // left2 Join2 (common Join1 right1) + edge1Before2 = threeRightJoin(leftPlan2, edge2, commonPlan.get(0), edge1, rightPlan1); + // (left2 Join2 common) join1 right1 + edge2Before1 = threeLeftJoin(leftPlan2, edge2, commonPlan.get(0), edge1, rightPlan1); + } else if (isSubPlan(rightPlan1, edge1.getRight(), leftPlan2, edge2.getLeft(), commonPlan)) { + // (left1 Join1 common) Join2 right2 + edge1Before2 = threeLeftJoin(leftPlan1, edge1, commonPlan.get(0), edge2, rightPlan2); + // left1 Join1 (common Join2 right2) + edge2Before1 = threeRightJoin(leftPlan1, edge1, commonPlan.get(0), edge2, rightPlan2); + } else if (isSubPlan(rightPlan1, edge1.getRight(), rightPlan2, edge2.getRight(), commonPlan)) { + // left2 Join2 (left1 Join1 common) + edge1Before2 = threeRightJoin(leftPlan2, edge2, leftPlan1, edge1, commonPlan.get(0)); + // left1 Join1 (left2 Join2 common) + edge2Before1 = threeRightJoin(leftPlan1, edge1, leftPlan2, edge2, commonPlan.get(0)); + } else { + return Optional.empty(); + } + // edge1 is not the neighborhood of edge2 + return Optional.of(orderJoin(edge1Before2, edge2Before1, edgeIndex1, edgeIndex2)); + } + + Edge threeLeftJoin(Plan plan1, Edge edge1, Plan plan2, Edge edge2, Plan plan3) { + // (plan1 edge1 plan2) edge2 plan3 + LogicalJoin join = simulateJoin(simulateJoin(plan1, edge1.getJoin(), plan2), + edge2.getJoin(), plan3); + Edge edge = new Edge(join, -1); + edge.addLeftNodes(edge1.getLeft(), edge1.getRight(), edge2.getLeft()); + edge.addRightNode(edge2.getRight()); + return edge; + } + + Edge threeRightJoin(Plan plan1, Edge edge1, Plan plan2, Edge edge2, Plan plan3) { + // plan1 edge1 (plan2 edge2 plan3) + LogicalJoin join = simulateJoin(plan1, edge1.getJoin(), + simulateJoin(plan2, edge2.getJoin(), plan3)); + Edge edge = new Edge(join, -1); + edge.addLeftNode(edge1.getLeft()); + edge.addRightNodes(edge2.getRight(), edge2.getLeft(), edge1.getRight()); + return edge; + } + + private Group getGroup(Plan plan) { + if (plan instanceof GroupPlan) { + return ((GroupPlan) plan).getGroup(); + } + assert plan.getGroupExpression().isPresent() : "All plan in GraphSimplifier must have a group"; + return plan.getGroupExpression().get().getOwnerGroup(); + } + + private SimplificationStep orderJoin(Edge edge1Before2, Edge edge2Before1, + int edgeIndex1, int edgeIndex2) { + double cost1Before2 = getSimpleCost(edge1Before2.getJoin()); + double cost2Before1 = getSimpleCost(edge2Before1.getJoin()); + double benefit = Double.MAX_VALUE; + SimplificationStep step; + // Choose the plan with smaller cost and make the simplification step to replace the old edge by it. + if (cost1Before2 < cost2Before1) { + if (cost1Before2 != 0) { + benefit = cost2Before1 / cost1Before2; + } + step = new SimplificationStep(benefit, edgeIndex1, edgeIndex2, + edge1Before2.getJoin().left(), edge1Before2.getJoin().right(), + edge1Before2.getLeft(), edge2Before1.getRight()); + } else { + if (cost2Before1 != 0) { + benefit = cost1Before2 / cost2Before1; + } + step = new SimplificationStep(benefit, edgeIndex2, edgeIndex1, + edge2Before1.getJoin().left(), edge2Before1.getJoin().right(), + edge2Before1.getLeft(), edge2Before1.getRight()); + } + return step; + } + + /** + * This function check whether the plan1 is a sub-plan of plan2 or the opposite + * @param plan1 the fist plan + * @param bitSet1 the reference nodes of the first plan + * @param plan2 the second plan + * @param bitSet2 the reference nodes of the second plan + * @param commonPlan the super plan is store here + * @return whether the plan1 is a sub-plan of plan2 or the opposite + */ + private boolean isSubPlan(Plan plan1, BitSet bitSet1, Plan plan2, BitSet bitSet2, List<Plan> commonPlan) { + if (isSubset(bitSet1, bitSet2)) { + commonPlan.add(plan2); + return true; + } else if (isSubset(bitSet2, bitSet1)) { + commonPlan.add(plan1); + return true; + } + return false; + } + + private double getSimpleCost(Plan plan) { + if (plan instanceof GroupPlan) { + return ((GroupPlan) plan).getGroup().getStatistics().getRowCount(); + } + return plan.getGroupExpression().get().getCostByProperties(PhysicalProperties.ANY); + } + + private LogicalJoin simulateJoin(Plan plan1, LogicalJoin join, Plan plan2) { + // In Graph Simplifier, we use the simple cost model, that is + // Plan.cost = Plan.rowCount + Plan.children1.cost + ... + // The reason is that this cost model has ASI (adjacent sequence interchange) property. + // TODO: consider network, data distribution cost + double cost = 0; + LogicalJoin newJoin = new LogicalJoin(join.getJoinType(), plan1, plan2); + List<Group> children = new ArrayList<>(); + cost += getGroup(plan1).getStatistics().getRowCount(); + children.add(getGroup(plan1)); + cost += getGroup(plan2).getStatistics().getRowCount(); + children.add(getGroup(plan2)); + + GroupExpression groupExpression = new GroupExpression(newJoin, children); + Group group = new Group(); + group.addGroupExpression(groupExpression); + StatsCalculator.estimate(groupExpression); + cost += group.getStatistics().getRowCount(); + + List<PhysicalProperties> inputs = new ArrayList<>(); + inputs.add(PhysicalProperties.ANY); + inputs.add(PhysicalProperties.ANY); + groupExpression.updateLowestCostTable(PhysicalProperties.ANY, inputs, cost); + + return (LogicalJoin) newJoin.withGroupExpression(Optional.of(groupExpression)); + } + + private void proposeJoin(int edgeIndex, Plan plan1, Plan plan2) { Review Comment: done -- This is an automated message from the Apache Git Service. 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