feat: Stage based fallback #4519
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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.comet.rules | ||
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| import org.apache.spark.internal.Logging | ||
| import org.apache.spark.sql.SparkSession | ||
| import org.apache.spark.sql.catalyst.rules.Rule | ||
| import org.apache.spark.sql.comet.{CometColumnarToRowExec, CometExec, CometNativeColumnarToRowExec, CometSparkToColumnarExec} | ||
| import org.apache.spark.sql.execution.{ColumnarToRowExec, ColumnarToRowTransition, RowToColumnarExec, SparkPlan} | ||
| import org.apache.spark.sql.execution.adaptive.QueryStageExec | ||
| import org.apache.spark.sql.execution.exchange.{BroadcastExchangeLike, ShuffleExchangeLike} | ||
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| import org.apache.comet.CometConf | ||
| import org.apache.comet.CometSparkSessionExtensions.withFallbackReason | ||
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| /** | ||
| * Reverts a query stage to Spark row-based execution when it has too many columnar-to-row (C2R) | ||
| * transitions. Each C2R indicates Comet could not keep execution columnar and had to fall back. | ||
| * With columnar shuffle enabled, each C2R implies a corresponding R2C round-trip. | ||
| */ | ||
| case class RevertNativeForTransitionHeavyStages(session: SparkSession) | ||
| extends Rule[SparkPlan] | ||
| with Logging { | ||
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| private def enabled = CometConf.COMET_EXEC_TRANSITION_REVERT_ENABLED.get() | ||
| private def maxTransitions = CometConf.COMET_EXEC_TRANSITION_REVERT_MAX_TRANSITIONS.get() | ||
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| override def apply(plan: SparkPlan): SparkPlan = { | ||
| if (!enabled) return plan | ||
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| if (session.sessionState.conf.adaptiveExecutionEnabled) { | ||
| applyForAQE(plan) | ||
| } else { | ||
| applyForNonAQE(plan) | ||
| } | ||
| } | ||
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| private def applyForAQE(plan: SparkPlan): SparkPlan = { | ||
| plan match { | ||
| case _: BroadcastExchangeLike => plan | ||
| case exchange: ShuffleExchangeLike => | ||
| revertStageIfNeeded(exchange.child, exchange.supportsColumnar) | ||
| .map(reverted => exchange.withNewChildren(Seq(reverted))) | ||
| .getOrElse(plan) | ||
| case _ => | ||
| // Result stage: its output is collected as rows, so no consumer requires columnar input | ||
| // and the reverted stage needs no trailing R2C. | ||
| revertStageIfNeeded(plan, outputColumnar = false).getOrElse(plan) | ||
| } | ||
| } | ||
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| private def applyForNonAQE(plan: SparkPlan): SparkPlan = { | ||
| val withRevertedStages = plan.transformUp { case exchange: ShuffleExchangeLike => | ||
| revertStageIfNeeded(exchange.child, exchange.supportsColumnar) | ||
| .map(reverted => exchange.withNewChildren(Seq(reverted))) | ||
| .getOrElse(exchange) | ||
| } | ||
| revertStageIfNeeded(withRevertedStages, outputColumnar = false) | ||
| .getOrElse(withRevertedStages) | ||
| } | ||
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| /** | ||
| * Reverts the stage if C2R count exceeds threshold. Wraps in R2C if exchange needs columnar. | ||
| */ | ||
| private def revertStageIfNeeded( | ||
| stagePlan: SparkPlan, | ||
| outputColumnar: Boolean): Option[SparkPlan] = { | ||
| val transitionCount = countTransitions(stagePlan) | ||
| if (transitionCount <= maxTransitions) return None | ||
|
Contributor
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| val reason = | ||
| s"Stage reverted: $transitionCount C2R transitions exceed threshold $maxTransitions" | ||
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| val reverted = revertToSpark(stagePlan) | ||
| val result = if (outputColumnar && !reverted.supportsColumnar) { | ||
| RowToColumnarExec(withFallbackReason(reverted, reason)) | ||
| } else { | ||
| withFallbackReason(reverted, reason) | ||
| } | ||
| Some(result) | ||
| } | ||
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| /** | ||
| * A node that marks the boundary between this stage and an adjacent one. | ||
| */ | ||
| private def isStageBoundary(plan: SparkPlan): Boolean = plan match { | ||
| case _: QueryStageExec | _: ShuffleExchangeLike | _: BroadcastExchangeLike => true | ||
| case _ => false | ||
| } | ||
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| /** | ||
| * Like `transformDown`, never descends stage-boundary children. | ||
| */ | ||
| private def transformStageDown(plan: SparkPlan)( | ||
| rule: PartialFunction[SparkPlan, SparkPlan]): SparkPlan = { | ||
| val transformed = rule.applyOrElse(plan, identity[SparkPlan]) | ||
| val newChildren = transformed.children.map { child => | ||
| if (isStageBoundary(child)) child else transformStageDown(child)(rule) | ||
| } | ||
| if (newChildren == transformed.children) transformed | ||
| else transformed.withNewChildren(newChildren) | ||
| } | ||
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| /** Like `transformUp`, never descends stage-boundary children. */ | ||
| private def transformStageUp(plan: SparkPlan)( | ||
| rule: PartialFunction[SparkPlan, SparkPlan]): SparkPlan = { | ||
| val newChildren = plan.children.map { child => | ||
| if (isStageBoundary(child)) child else transformStageUp(child)(rule) | ||
| } | ||
| val withNewChildren = | ||
| if (newChildren == plan.children) plan else plan.withNewChildren(newChildren) | ||
| rule.applyOrElse(withNewChildren, identity[SparkPlan]) | ||
| } | ||
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| /** Counts C2R transitions within this stage, stopping at stage boundaries. */ | ||
| private[rules] def countTransitions(plan: SparkPlan): Int = { | ||
| var count = 0 | ||
| def visit(node: SparkPlan): Unit = node match { | ||
| case _ if isStageBoundary(node) => () | ||
| case _: ColumnarToRowTransition => | ||
| count += 1 | ||
| node.children.foreach(visit) | ||
| case _ => | ||
| node.children.foreach(visit) | ||
| } | ||
| visit(plan) | ||
| count | ||
| } | ||
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| private[rules] def revertToSpark(plan: SparkPlan): SparkPlan = { | ||
| val stripped = transformStageDown(plan) { | ||
| case CometNativeColumnarToRowExec(child) => child | ||
| case CometColumnarToRowExec(child) => child | ||
| case ColumnarToRowExec(child) => child | ||
| case sparkToColumnar: CometSparkToColumnarExec => sparkToColumnar.child | ||
| case RowToColumnarExec(child) => child | ||
| } | ||
| val reverted = transformStageUp(stripped) { case cometExec: CometExec => | ||
| if (cometExec.originalPlan.children.size == cometExec.children.size) { | ||
| cometExec.originalPlan.withNewChildren(cometExec.children) | ||
| } else { | ||
| logWarning( | ||
| "Comet plan and original have different child count for " + | ||
| s"${cometExec.getClass.getSimpleName}, using originalPlan as-is.") | ||
| cometExec.originalPlan | ||
| } | ||
| } | ||
| insertTransitions(reverted) | ||
| } | ||
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| private def insertTransitions(plan: SparkPlan): SparkPlan = { | ||
| // transformStageUp never descends into stage-boundary nodes (QueryStageExec, exchanges), so | ||
| // this only needs to bridge row nodes that still have a columnar child within the stage. | ||
| transformStageUp(plan) { | ||
| case node if !node.supportsColumnar => | ||
| val newChildren = node.children.map { child => | ||
| if (child.supportsColumnar) ColumnarToRowExec(child) else child | ||
|
parthchandra marked this conversation as resolved.
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| } | ||
| if (newChildren != node.children) node.withNewChildren(newChildren) else node | ||
| } | ||
| } | ||
| } | ||
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parthchandra marked this conversation as resolved.
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Why is there no
case _ =>arm like in the AQE case.There was a problem hiding this comment.
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Added
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I don't see it
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This handles the final stage, since case match on
Exchnageabove(usingtransformUp) cannot catch it, which is the equivalent ofcase _(ResultStage) in AQE flow