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[feature](Nereids): rewrite count(null) to 0 (#27471)

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select count(null) --> select 0
This commit is contained in:
谢健
2023-11-28 16:25:34 +08:00
committed by GitHub
parent c203d36300
commit 3d46643dab
5 changed files with 120 additions and 10 deletions
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4
fe/fe-core/src/main/java/org/apache/doris/nereids/jobs/executor/Rewriter.java
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@ -48,7 +48,7 @@ import org.apache.doris.nereids.rules.rewrite.CollectProjectAboveConsumer;
import org.apache.doris.nereids.rules.rewrite.ColumnPruning;
import org.apache.doris.nereids.rules.rewrite.ConvertInnerOrCrossJoin;
import org.apache.doris.nereids.rules.rewrite.CountDistinctRewrite;
import org.apache.doris.nereids.rules.rewrite.CountLiteralToCountStar;
import org.apache.doris.nereids.rules.rewrite.CountLiteralRewrite;
import org.apache.doris.nereids.rules.rewrite.CreatePartitionTopNFromWindow;
import org.apache.doris.nereids.rules.rewrite.DeferMaterializeTopNResult;
import org.apache.doris.nereids.rules.rewrite.EliminateAggregate;
@ -194,7 +194,7 @@ public class Rewriter extends AbstractBatchJobExecutor {
topDown(
new SimplifyAggGroupBy(),
new NormalizeAggregate(),
new CountLiteralToCountStar(),
new CountLiteralRewrite(),
new NormalizeSort()
),
topic("Window analysis",

2
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/RuleType.java
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@ -59,7 +59,7 @@ public enum RuleType {
BINDING_INSERT_TARGET_TABLE(RuleTypeClass.REWRITE),
BINDING_INSERT_FILE(RuleTypeClass.REWRITE),
COUNT_LITERAL_TO_COUNT_STAR(RuleTypeClass.REWRITE),
COUNT_LITERAL_REWRITE(RuleTypeClass.REWRITE),
REPLACE_SORT_EXPRESSION_BY_CHILD_OUTPUT(RuleTypeClass.REWRITE),
FILL_UP_HAVING_AGGREGATE(RuleTypeClass.REWRITE),

46
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/CountLiteralToCountStar.java → fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/CountLiteralRewrite.java
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@ -23,6 +23,9 @@ import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.NamedExpression;
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.literal.BigIntLiteral;
import org.apache.doris.nereids.trees.plans.Plan;
import org.apache.doris.nereids.trees.plans.logical.LogicalProject;
import com.google.common.collect.Lists;
@ -30,22 +33,43 @@ import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;
/**
* count(1) ==> count(*)
* count(null) ==> 0
*/
public class CountLiteralToCountStar extends OneRewriteRuleFactory {
public class CountLiteralRewrite extends OneRewriteRuleFactory {
@Override
public Rule build() {
return logicalAggregate().then(
agg -> {
List<NamedExpression> newExprs = Lists.newArrayListWithCapacity(agg.getOutputExpressions().size());
if (rewriteCountLiteral(agg.getOutputExpressions(), newExprs)) {
return agg.withAggOutput(newExprs);
if (!rewriteCountLiteral(agg.getOutputExpressions(), newExprs)) {
// no need to rewrite
return agg;
}
Map<Boolean, List<NamedExpression>> projectsAndAggFunc = newExprs.stream()
.collect(Collectors.partitioningBy(Expression::isConstant));
if (projectsAndAggFunc.get(false).isEmpty()) {
// if there is no group by keys and other agg func, don't rewrite
return null;
} else {
// if there is group by keys, put count(null) in projects, such as
// project(0 as count(null))
// --Aggregate(k1, group by k1)
Plan plan = agg.withAggOutput(projectsAndAggFunc.get(false));
if (!projectsAndAggFunc.get(true).isEmpty()) {
projectsAndAggFunc.get(false).stream().map(NamedExpression::toSlot)
.forEach(projectsAndAggFunc.get(true)::add);
plan = new LogicalProject<>(projectsAndAggFunc.get(true), plan);
}
return plan;
}
return agg;
}
).toRule(RuleType.COUNT_LITERAL_TO_COUNT_STAR);
).toRule(RuleType.COUNT_LITERAL_REWRITE);
}
private boolean rewriteCountLiteral(List<NamedExpression> oldExprs, List<NamedExpression> newExprs) {
@ -55,7 +79,7 @@ public class CountLiteralToCountStar extends OneRewriteRuleFactory {
Set<AggregateFunction> oldAggFuncSet = expr.collect(AggregateFunction.class::isInstance);
oldAggFuncSet.stream()
.filter(this::isCountLiteral)
.forEach(c -> replaced.put(c, new Count()));
.forEach(c -> replaced.put(c, rewrite((Count) c)));
expr = expr.rewriteUp(s -> replaced.getOrDefault(s, s));
changed |= !replaced.isEmpty();
newExprs.add((NamedExpression) expr);
@ -66,6 +90,14 @@ public class CountLiteralToCountStar extends OneRewriteRuleFactory {
private boolean isCountLiteral(AggregateFunction aggFunc) {
return !aggFunc.isDistinct()
&& aggFunc instanceof Count
&& aggFunc.children().stream().allMatch(e -> e.isLiteral() && !e.isNullLiteral());
&& aggFunc.children().size() == 1
&& aggFunc.child(0).isLiteral();
}
private Expression rewrite(Count count) {
if (count.child(0).isNullLiteral()) {
return new BigIntLiteral(0);
}
return new Count();
}
}

5
fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/Expression.java
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@ -23,6 +23,7 @@ import org.apache.doris.nereids.exceptions.AnalysisException;
import org.apache.doris.nereids.trees.AbstractTreeNode;
import org.apache.doris.nereids.trees.expressions.functions.ExpressionTrait;
import org.apache.doris.nereids.trees.expressions.functions.Nondeterministic;
import org.apache.doris.nereids.trees.expressions.functions.agg.AggregateFunction;
import org.apache.doris.nereids.trees.expressions.literal.Literal;
import org.apache.doris.nereids.trees.expressions.literal.NullLiteral;
import org.apache.doris.nereids.trees.expressions.shape.LeafExpression;
@ -224,6 +225,10 @@ public abstract class Expression extends AbstractTreeNode<Expression> implements
* Whether the expression is a constant.
*/
public boolean isConstant() {
if (this instanceof AggregateFunction) {
// agg_fun(literal) is not constant, the result depends on the group by keys
return false;
}
if (this instanceof LeafExpression) {
return this instanceof Literal;
} else {

73
fe/fe-core/src/test/java/org/apache/doris/nereids/rules/rewrite/CountLiteralRewriteTest.java Normal file
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@ -0,0 +1,73 @@
// 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.trees.expressions.functions.agg.Count;
import org.apache.doris.nereids.util.MemoPatternMatchSupported;
import org.apache.doris.nereids.util.PlanChecker;
import org.apache.doris.utframe.TestWithFeService;
import org.junit.jupiter.api.Test;
/**
* CountLiteralRewriteTest
*/
class CountLiteralRewriteTest extends TestWithFeService implements MemoPatternMatchSupported {
@Override
protected void runBeforeAll() throws Exception {
createDatabase("test");
createTable("create table test.student (\n" + "id int not null,\n" + "name varchar(128),\n"
+ "age int, sex int)\n" + "distributed by hash(id) buckets 10\n"
+ "properties('replication_num' = '1');");
connectContext.setDatabase("default_cluster:test");
}
@Test
void testCountLiteral() {
PlanChecker.from(connectContext)
.analyze("select count(1) as c from student group by id")
.rewrite()
.matches(logicalAggregate()
.when(agg -> agg.getOutputExpressions().stream()
.allMatch(expr -> expr.anyMatch(c -> !(c instanceof Count) || ((Count) c).isCountStar()))))
.printlnTree();
PlanChecker.from(connectContext)
.analyze("select count(1), sum(id) from student")
.rewrite()
.matches(logicalAggregate()
.when(agg -> agg.getOutputExpressions().stream()
.allMatch(expr -> expr.anyMatch(c -> !(c instanceof Count) || ((Count) c).isCountStar()))))
.printlnTree();
}
@Test
void testCountNull() {
PlanChecker.from(connectContext)
.analyze("select count(null) as c from student group by id")
.rewrite()
.matches(logicalAggregate().when(agg -> agg.getExpressions().stream().noneMatch(Count.class::isInstance)))
.printlnTree();
PlanChecker.from(connectContext)
.analyze("select count(null) as c, sum(id) from student")
.rewrite()
.matches(logicalAggregate().when(agg -> agg.getExpressions().stream().noneMatch(Count.class::isInstance)))
.printlnTree();
}
}