EmmyMiao87 commented on code in PR #8947: URL: https://github.com/apache/incubator-doris/pull/8947#discussion_r855940321
########## fe/fe-core/src/main/java/org/apache/doris/statistics/BaseStatsDerive.java: ########## @@ -0,0 +1,158 @@ +// 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.statistics; + +import com.google.common.base.Preconditions; +import com.google.common.collect.Lists; +import org.apache.doris.analysis.Expr; +import org.apache.doris.analysis.SlotId; +import org.apache.doris.common.UserException; +import org.apache.doris.planner.PlanNode; +import org.apache.logging.log4j.LogManager; +import org.apache.logging.log4j.Logger; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.HashMap; +import java.util.List; + +public class BaseStatsDerive { + private static final Logger LOG = LogManager.getLogger(BaseStatsDerive.class); + // estimate of the output rowCount of this node; + // invalid: -1 + protected long rowCount = -1; + protected long limit = -1; + + protected List<Expr> conjuncts = Lists.newArrayList(); + protected List<StatsDeriveResult> childrenStatsResult = Lists.newArrayList(); + + protected void init(PlanNode node) throws UserException { + limit = node.getLimit(); + conjuncts.addAll(node.getConjuncts()); + + for (PlanNode childNode : node.getChildren()) { + StatsDeriveResult result = childNode.getStatsDeriveResult(); + if (result == null) { + throw new UserException("childNode statsDeriveResult is null, childNodeType is " + childNode.getNodeType() + + "parentNodeType is " + node.getNodeType()); + } + childrenStatsResult.add(result); + } + } + + public StatsDeriveResult deriveStats() { + return new StatsDeriveResult(deriveRowCount(), deriveColumnToDataSize(), deriveColumnToNdv()); + } + + public boolean hasLimit() { + return limit > -1; + } + + protected void applyConjunctsSelectivity() { + if (rowCount == -1) { + return; + } + applySelectivity(); + } + + private void applySelectivity() { + double selectivity = computeSelectivity(); + Preconditions.checkState(rowCount >= 0); + long preConjunctrowCount = rowCount; + rowCount = Math.round(rowCount * selectivity); + // don't round rowCount down to zero for safety. + if (rowCount == 0 && preConjunctrowCount > 0) { + rowCount = 1; + } + } + + protected double computeSelectivity() { + for (Expr expr : conjuncts) { + expr.setSelectivity(); + } + return computeCombinedSelectivity(conjuncts); + } + + /** + * Returns the estimated combined selectivity of all conjuncts. Uses heuristics to + * address the following estimation challenges: + * 1. The individual selectivities of conjuncts may be unknown. + * 2. Two selectivities, whether known or unknown, could be correlated. Assuming + * independence can lead to significant underestimation. + * <p> + * The first issue is addressed by using a single default selectivity that is + * representative of all conjuncts with unknown selectivities. + * The second issue is addressed by an exponential backoff when multiplying each + * additional selectivity into the final result. + */ + protected double computeCombinedSelectivity(List<Expr> conjuncts) { + // Collect all estimated selectivities. + List<Double> selectivities = new ArrayList<>(); + for (Expr e : conjuncts) { + if (e.hasSelectivity()) selectivities.add(e.getSelectivity()); + } + if (selectivities.size() != conjuncts.size()) { + // Some conjuncts have no estimated selectivity. Use a single default + // representative selectivity for all those conjuncts. + selectivities.add(Expr.DEFAULT_SELECTIVITY); + } + // Sort the selectivities to get a consistent estimate, regardless of the original + // conjunct order. Sort in ascending order such that the most selective conjunct + // is fully applied. + Collections.sort(selectivities); + double result = 1.0; + // selectivity = 1 * (s1)^(1/1) * (s2)^(1/2) * ... * (sn-1)^(1/(n-1)) * (sn)^(1/n) + for (int i = 0; i < selectivities.size(); ++i) { + // Exponential backoff for each selectivity multiplied into the final result. + result *= Math.pow(selectivities.get(i), 1.0 / (double) (i + 1)); + } + // Bound result in [0, 1] + return Math.max(0.0, Math.min(1.0, result)); + } + + protected void capRowCountAtLimit() { + if (hasLimit()) { + rowCount = rowCount == -1 ? limit : Math.min(rowCount, limit); + } + } + + + // Currently it simply adds the number of rows of children + protected long deriveRowCount() { + applyConjunctsSelectivity(); Review Comment: ```suggestion rowcount = children max(rowcount) applyConjunctsSelectivity(); ``` ########## fe/fe-core/src/main/java/org/apache/doris/planner/OlapScanNode.java: ########## @@ -386,6 +403,18 @@ public void computeStats(Analyzer analyzer) { } // when node scan has no data, cardinality should be 0 instead of a invalid value after computeStats() cardinality = cardinality == -1 ? 0 : cardinality; + + // update statsDeriveResult for real statistics + // After statistics collection is complete, remove the logic + if (analyzer.safeIsEnableJoinReorderBasedCost()) { + statsDeriveResult.setRowCount(cardinality); Review Comment: Only keep this line ########## fe/fe-core/src/main/java/org/apache/doris/planner/OlapScanNode.java: ########## @@ -386,6 +403,18 @@ public void computeStats(Analyzer analyzer) { } // when node scan has no data, cardinality should be 0 instead of a invalid value after computeStats() cardinality = cardinality == -1 ? 0 : cardinality; + + // update statsDeriveResult for real statistics + // After statistics collection is complete, remove the logic + if (analyzer.safeIsEnableJoinReorderBasedCost()) { + statsDeriveResult.setRowCount(cardinality); + for (Map.Entry<SlotId, Long> entry : statsDeriveResult.getColumnToNdv().entrySet()) { Review Comment: remove from 411 ~ 416 -- This is an automated message from the Apache Git Service. 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