xzj7019 commented on code in PR #28143: URL: https://github.com/apache/doris/pull/28143#discussion_r1420205675
########## fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/PushDownCountThroughJoinOneSide.java: ########## @@ -0,0 +1,216 @@ +// 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; + +import org.apache.doris.nereids.rules.Rule; +import org.apache.doris.nereids.rules.RuleType; +import org.apache.doris.nereids.trees.expressions.Alias; +import org.apache.doris.nereids.trees.expressions.Expression; +import org.apache.doris.nereids.trees.expressions.NamedExpression; +import org.apache.doris.nereids.trees.expressions.Slot; +import org.apache.doris.nereids.trees.expressions.functions.agg.AggregateFunction; +import org.apache.doris.nereids.trees.expressions.functions.agg.Count; +import org.apache.doris.nereids.trees.expressions.functions.agg.Sum; +import org.apache.doris.nereids.trees.plans.Plan; +import org.apache.doris.nereids.trees.plans.logical.LogicalAggregate; +import org.apache.doris.nereids.trees.plans.logical.LogicalJoin; +import org.apache.doris.nereids.trees.plans.logical.LogicalProject; + +import com.google.common.base.Preconditions; +import com.google.common.collect.ImmutableList; +import com.google.common.collect.ImmutableList.Builder; + +import java.util.ArrayList; +import java.util.HashMap; +import java.util.HashSet; +import java.util.List; +import java.util.Map; +import java.util.Set; + +/** + * TODO: distinct | just push one level + * Support Pushdown Count(col). + * Count(col) -> Sum( cnt ) + * <p> + * Related paper "Eager aggregation and lazy aggregation". + * <pre> + * aggregate: count(x) + * | + * join + * | \ + * | * + * (x) + * -> + * aggregate: Sum( cnt ) + * | + * join + * | \ + * | * + * aggregate: count(x) as cnt + * </pre> + * Notice: rule can't optimize condition that groupby is empty when Count(*) exists. + */ +public class PushDownCountThroughJoinOneSide implements RewriteRuleFactory { + @Override + public List<Rule> buildRules() { + return ImmutableList.of( + logicalAggregate(innerLogicalJoin()) + .when(agg -> agg.child().getOtherJoinConjuncts().isEmpty()) + .whenNot(agg -> agg.child().children().stream().anyMatch(p -> p instanceof LogicalAggregate)) + .when(agg -> agg.getGroupByExpressions().stream().allMatch(e -> e instanceof Slot)) + .when(agg -> { + Set<AggregateFunction> funcs = agg.getAggregateFunctions(); + return !funcs.isEmpty() && funcs.stream() + .allMatch(f -> f instanceof Count && !f.isDistinct() + && (!((Count) f).isCountStar() && f.child(0) instanceof Slot)); + }) + .thenApply(ctx -> { + Set<Integer> enableNereidsRules = ctx.cascadesContext.getConnectContext() + .getSessionVariable().getEnableNereidsRules(); + if (!enableNereidsRules.contains(RuleType.PUSH_DOWN_COUNT_THROUGH_JOIN_ONE_SIDE.type())) { + return null; + } + LogicalAggregate<LogicalJoin<Plan, Plan>> agg = ctx.root; + return pushCount(agg, agg.child(), ImmutableList.of()); + }) + .toRule(RuleType.PUSH_DOWN_COUNT_THROUGH_JOIN_ONE_SIDE), + logicalAggregate(logicalProject(innerLogicalJoin())) + .when(agg -> agg.child().isAllSlots()) + .when(agg -> agg.child().child().getOtherJoinConjuncts().isEmpty()) + .whenNot(agg -> agg.child().children().stream().anyMatch(p -> p instanceof LogicalAggregate)) + .when(agg -> agg.getGroupByExpressions().stream().allMatch(e -> e instanceof Slot)) + .when(agg -> { + Set<AggregateFunction> funcs = agg.getAggregateFunctions(); + return !funcs.isEmpty() && funcs.stream() + .allMatch(f -> f instanceof Count && !f.isDistinct() + && (!((Count) f).isCountStar() && f.child(0) instanceof Slot)); + }) + .thenApply(ctx -> { + Set<Integer> enableNereidsRules = ctx.cascadesContext.getConnectContext() + .getSessionVariable().getEnableNereidsRules(); + if (!enableNereidsRules.contains(RuleType.PUSH_DOWN_COUNT_THROUGH_JOIN_ONE_SIDE.type())) { + return null; + } + LogicalAggregate<LogicalProject<LogicalJoin<Plan, Plan>>> agg = ctx.root; + return pushCount(agg, agg.child().child(), agg.child().getProjects()); + }) + .toRule(RuleType.PUSH_DOWN_COUNT_THROUGH_JOIN_ONE_SIDE) + ); + } + + private LogicalAggregate<Plan> pushCount(LogicalAggregate<? extends Plan> agg, + LogicalJoin<Plan, Plan> join, List<NamedExpression> projects) { + List<Slot> leftOutput = join.left().getOutput(); + List<Slot> rightOutput = join.right().getOutput(); + + List<Count> leftCounts = new ArrayList<>(); + List<Count> rightCounts = new ArrayList<>(); + for (AggregateFunction f : agg.getAggregateFunctions()) { + Count count = (Count) f; + Slot slot = (Slot) count.child(0); + if (leftOutput.contains(slot)) { + leftCounts.add(count); + } else if (rightOutput.contains(slot)) { + rightCounts.add(count); + } else { + throw new IllegalStateException("Slot " + slot + " not found in join output"); + } + } + + Set<Slot> leftGroupBy = new HashSet<>(); + Set<Slot> rightGroupBy = new HashSet<>(); + for (Expression e : agg.getGroupByExpressions()) { + Slot slot = (Slot) e; + if (leftOutput.contains(slot)) { + leftGroupBy.add(slot); + } else if (rightOutput.contains(slot)) { + rightGroupBy.add(slot); + } else { + return null; + } + } + join.getHashJoinConjuncts().forEach(e -> e.getInputSlots().forEach(slot -> { + if (leftOutput.contains(slot)) { + leftGroupBy.add(slot); + } else if (rightOutput.contains(slot)) { + rightGroupBy.add(slot); + } else { + throw new IllegalStateException("Slot " + slot + " not found in join output"); + } + })); + + Plan left = join.left(); + Plan right = join.right(); + + Map<Slot, NamedExpression> leftCntSlotToOutput = new HashMap<>(); + Map<Slot, NamedExpression> rightCntSlotToOutput = new HashMap<>(); + + // left Count agg + if (!leftCounts.isEmpty()) { + Builder<NamedExpression> leftCntAggOutputBuilder = ImmutableList.<NamedExpression>builder() + .addAll(leftGroupBy); + leftCounts.forEach(func -> { + Alias alias = func.alias(func.getName()); + leftCntSlotToOutput.put((Slot) func.child(0), alias); + leftCntAggOutputBuilder.add(alias); + }); + left = new LogicalAggregate<>(ImmutableList.copyOf(leftGroupBy), leftCntAggOutputBuilder.build(), + join.left()); + } + + // right Count agg + if (!rightCounts.isEmpty()) { + Builder<NamedExpression> rightCntAggOutputBuilder = ImmutableList.<NamedExpression>builder() + .addAll(rightGroupBy); + rightCounts.forEach(func -> { + Alias alias = func.alias(func.getName()); + rightCntSlotToOutput.put((Slot) func.child(0), alias); + rightCntAggOutputBuilder.add(alias); + }); + + right = new LogicalAggregate<>(ImmutableList.copyOf(rightGroupBy), rightCntAggOutputBuilder.build(), + join.right()); + } + + Preconditions.checkState(left != join.left() || right != join.right()); + Plan newJoin = join.withChildren(left, right); + + // top Sum agg + // count(slot) -> sum( count(slot) as cnt ) + List<NamedExpression> newOutputExprs = new ArrayList<>(); + for (NamedExpression ne : agg.getOutputExpressions()) { + if (ne instanceof Alias && ((Alias) ne).child() instanceof Count) { + Count oldTopCnt = (Count) ((Alias) ne).child(); + + Slot slot = (Slot) oldTopCnt.child(0); + if (leftCntSlotToOutput.containsKey(slot)) { Review Comment: would we do some pre-processing ahead, such as judge which side will push down, and at this point, we just do the transformation without the additional 'if-else'? 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