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HIVE-23723: Limit operator pushdown through LOJ (Attila Magyar, revie…
…wed by Krisztian Kasa)
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154 changes: 154 additions & 0 deletions
154
ql/src/java/org/apache/hadoop/hive/ql/optimizer/OrderlessLimitPushDownOptimizer.java
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| * | ||
| * * 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. | ||
| * | ||
| */ | ||
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| package org.apache.hadoop.hive.ql.optimizer; | ||
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| import static org.apache.hadoop.hive.ql.optimizer.topnkey.TopNKeyProcessor.copyDown; | ||
| import static org.apache.hadoop.hive.ql.optimizer.topnkey.TopNKeyPushdownProcessor.moveDown; | ||
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| import java.util.ArrayList; | ||
| import java.util.LinkedHashMap; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
| import java.util.Stack; | ||
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| import org.apache.hadoop.hive.ql.exec.CommonJoinOperator; | ||
| import org.apache.hadoop.hive.ql.exec.LimitOperator; | ||
| import org.apache.hadoop.hive.ql.exec.Operator; | ||
| import org.apache.hadoop.hive.ql.exec.ReduceSinkOperator; | ||
| import org.apache.hadoop.hive.ql.lib.DefaultGraphWalker; | ||
| import org.apache.hadoop.hive.ql.lib.DefaultRuleDispatcher; | ||
| import org.apache.hadoop.hive.ql.lib.Node; | ||
| import org.apache.hadoop.hive.ql.lib.NodeProcessorCtx; | ||
| import org.apache.hadoop.hive.ql.lib.RuleRegExp; | ||
| import org.apache.hadoop.hive.ql.lib.SemanticGraphWalker; | ||
| import org.apache.hadoop.hive.ql.lib.SemanticNodeProcessor; | ||
| import org.apache.hadoop.hive.ql.lib.SemanticRule; | ||
| import org.apache.hadoop.hive.ql.parse.ParseContext; | ||
| import org.apache.hadoop.hive.ql.parse.SemanticException; | ||
| import org.apache.hadoop.hive.ql.plan.JoinCondDesc; | ||
| import org.apache.hadoop.hive.ql.plan.JoinDesc; | ||
| import org.apache.hadoop.hive.ql.plan.LimitDesc; | ||
| import org.apache.hadoop.hive.ql.plan.OperatorDesc; | ||
| import org.slf4j.Logger; | ||
| import org.slf4j.LoggerFactory; | ||
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| /** | ||
| * Push LIMIT without an Order By through Selects and Left Outer Joins | ||
| */ | ||
| public class OrderlessLimitPushDownOptimizer extends Transform { | ||
| private static final Logger LOG = LoggerFactory.getLogger(OrderlessLimitPushDownOptimizer.class); | ||
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| @Override | ||
| public ParseContext transform(ParseContext pctx) throws SemanticException { | ||
| Map<SemanticRule, SemanticNodeProcessor> opRules = new LinkedHashMap<SemanticRule, SemanticNodeProcessor>(); | ||
| opRules.put( | ||
| new RuleRegExp("LIMIT push down", LimitOperator.getOperatorName() + "%"), | ||
| new LimitPushDown()); | ||
| SemanticGraphWalker walker = new DefaultGraphWalker(new DefaultRuleDispatcher(null, opRules, null)); | ||
| walker.startWalking(new ArrayList<>(pctx.getTopOps().values()), null); | ||
| return pctx; | ||
| } | ||
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| private static class LimitPushDown implements SemanticNodeProcessor { | ||
| @Override | ||
| public Object process(Node nd, Stack<Node> stack, NodeProcessorCtx procCtx, Object... nodeOutputs) throws SemanticException { | ||
| ReduceSinkOperator reduceSink = findReduceSink(stack); | ||
| if (reduceSink == null || !reduceSink.getConf().hasOrderBy()) { // LIMIT + ORDER BY handled by TopNKey push down | ||
| pushDown((LimitOperator) nd); | ||
| } | ||
| return null; | ||
| } | ||
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| private ReduceSinkOperator findReduceSink(Stack<Node> stack) { | ||
| for (int i = stack.size() - 2 ; i >= 0; i--) { | ||
| Operator<?> operator = (Operator<?>) stack.get(i); | ||
| if (operator instanceof ReduceSinkOperator) { | ||
| return ((ReduceSinkOperator) operator); | ||
| } | ||
| } | ||
| return null; | ||
| } | ||
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| private void pushDown(LimitOperator limit) throws SemanticException { | ||
| Operator<? extends OperatorDesc> parent = limit.getParentOperators().get(0); | ||
| if (parent.getNumChild() != 1) { | ||
| return; | ||
| } | ||
| switch (parent.getType()) { | ||
| case LIMIT: | ||
| combineLimits(limit); | ||
| break; | ||
| case SELECT: | ||
| case FORWARD: | ||
| pushdownThroughParent(limit); | ||
| break; | ||
| case MERGEJOIN: | ||
| case JOIN: | ||
| case MAPJOIN: | ||
| pushThroughLeftOuterJoin(limit); | ||
| break; | ||
| default: | ||
| break; | ||
| } | ||
| } | ||
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| private void combineLimits(LimitOperator childLimit) throws SemanticException { | ||
| LimitOperator parentLimit = (LimitOperator) childLimit.getParentOperators().get(0); | ||
| LimitDesc parentConf = parentLimit.getConf(); | ||
| LimitDesc childConf = childLimit.getConf(); | ||
| if (parentConf.getOffset() == childConf.getOffset()) { | ||
| int min = Math.min(parentConf.getLimit(), childConf.getLimit()); | ||
| LOG.debug("Combining two limits child={}, parent={}, newLimit={}", childLimit, parentLimit, min); | ||
| parentConf.setLimit(min); | ||
| parentLimit.removeChildAndAdoptItsChildren(childLimit); | ||
| pushDown(parentLimit); | ||
| } | ||
| } | ||
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| private void pushdownThroughParent(LimitOperator limit) throws SemanticException { | ||
| Operator<? extends OperatorDesc> parent = limit.getParentOperators().get(0); | ||
| LOG.debug("Pushing {} through {}", limit.getName(), parent.getName()); | ||
| moveDown(limit); | ||
| pushDown(limit); | ||
| } | ||
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| private void pushThroughLeftOuterJoin(LimitOperator limit) | ||
| throws SemanticException { | ||
| CommonJoinOperator<? extends JoinDesc> join = | ||
| (CommonJoinOperator<? extends JoinDesc>) limit.getParentOperators().get(0); | ||
| JoinCondDesc[] joinConds = join.getConf().getConds(); | ||
| JoinCondDesc firstJoinCond = joinConds[0]; | ||
| for (JoinCondDesc joinCond : joinConds) { | ||
| if (!firstJoinCond.equals(joinCond)) { | ||
| return; | ||
| } | ||
| } | ||
| if (firstJoinCond.getType() == JoinDesc.LEFT_OUTER_JOIN) { | ||
| List<Operator<? extends OperatorDesc>> joinInputs = join.getParentOperators(); | ||
| final ReduceSinkOperator reduceSinkOperator = (ReduceSinkOperator) joinInputs.get(0); | ||
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| pushDown((LimitOperator) copyDown(reduceSinkOperator, new LimitDesc(limit.getConf()))); | ||
| // the copied limit will take care of the offset, need to reset the offset in the original to not to lose rows | ||
| limit.getConf().setOffset(0); | ||
| } | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,33 @@ | ||
| --! qt:dataset:src | ||
| --! qt:dataset:alltypesorc | ||
| set hive.mapred.mode=nonstrict; | ||
| set hive.explain.user=false; | ||
| set hive.limit.pushdown.memory.usage=0.3f; | ||
| set hive.optimize.reducededuplication.min.reducer=1; | ||
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| -- SORT_QUERY_RESULTS | ||
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| -- push through LOJ | ||
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| set hive.optimize.limit=true; | ||
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| select 'positive LOJ'; | ||
| explain | ||
| SELECT src1.key, src2.value FROM src src1 LEFT OUTER JOIN src src2 ON (src1.key = src2.key) LIMIT 5; | ||
| SELECT src1.key, src2.value FROM src src1 LEFT OUTER JOIN src src2 ON (src1.key = src2.key) LIMIT 5; | ||
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| select 'negative - order'; | ||
| explain | ||
| SELECT src1.key, src2.value FROM src src1 LEFT OUTER JOIN src src2 ON (src1.key = src2.key) ORDER BY src1.key LIMIT 5; | ||
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| select 'negative - group by'; | ||
| explain | ||
| SELECT src1.key, count(src2.value) FROM src src1 LEFT OUTER JOIN src src2 ON (src1.key = src2.key) GROUP BY src1.key LIMIT 5; | ||
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| set hive.optimize.limit=false; | ||
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| select 'negative - disabled'; | ||
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| explain | ||
| SELECT src1.key, src2.value FROM src src1 LEFT OUTER JOIN src src2 ON (src1.key = src2.key) LIMIT 5; | ||
| SELECT src1.key, src2.value FROM src src1 LEFT OUTER JOIN src src2 ON (src1.key = src2.key) LIMIT 5; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,3 +1,4 @@ | ||
| --! qt:dataset:src | ||
| SET hive.vectorized.execution.enabled=true; | ||
| set hive.fetch.task.conversion=none; | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,3 +1,4 @@ | ||
| --! qt:dataset:src | ||
| set hive.fetch.task.conversion=none; | ||
| SET hive.vectorized.execution.enabled=true; | ||
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