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Posted to github@datafusion.apache.org by "andygrove (via GitHub)" <gi...@apache.org> on 2025/12/14 18:36:49 UTC

[PR] feat: Proof-of-concept of AQE cost-based optimization [datafusion-comet]

andygrove opened a new pull request, #2906:
URL: https://github.com/apache/datafusion-comet/pull/2906

   ## Which issue does this PR close?
   
   <!--
   We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. For example `Closes #123` indicates that this PR will close issue #123.
   -->
   
   Closes https://github.com/apache/datafusion-comet/issues/2785
   
   ## Rationale for this change
   
   <!--
    Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed.
    Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes.
   -->
   
   I would like to start experimenting with CBO and allow users to also experiment by providing their own cost models, tailored to their specific workloads.
   
   ## What changes are included in this PR?
   
   <!--
   There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR.
   -->
   
   Add a starting point for development and experimentation.
   
   ## How are these changes tested?
   
   <!--
   We typically require tests for all PRs in order to:
   1. Prevent the code from being accidentally broken by subsequent changes
   2. Serve as another way to document the expected behavior of the code
   
   If tests are not included in your PR, please explain why (for example, are they covered by existing tests)?
   -->
   
   Not at all yet. I will leave this as draft until it is farther along and has some tests, but I would like to get feedback early since this is a proof-of-concept.
   


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Re: [PR] feat: Proof-of-concept of AQE cost-based optimization [datafusion-comet]

Posted by "coderfender (via GitHub)" <gi...@apache.org>.
coderfender commented on code in PR #2906:
URL: https://github.com/apache/datafusion-comet/pull/2906#discussion_r2617426301


##########
spark/src/main/scala/org/apache/comet/cost/CometCostModel.scala:
##########
@@ -0,0 +1,103 @@
+/*
+ * 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.comet.cost
+
+import org.apache.spark.sql.catalyst.expressions.{BinaryArithmetic, Expression}
+import org.apache.spark.sql.comet.{CometColumnarToRowExec, CometPlan, CometProjectExec}
+import org.apache.spark.sql.comet.execution.shuffle.{CometColumnarShuffle, CometNativeShuffle, CometShuffleExchangeExec}
+import org.apache.spark.sql.execution.SparkPlan
+
+import org.apache.comet.DataTypeSupport
+
+case class CometCostEstimate(acceleration: Double)
+
+trait CometCostModel {
+
+  /** Estimate the relative cost of one operator */
+  def estimateCost(plan: SparkPlan): CometCostEstimate
+}
+
+class DefaultCometCostModel extends CometCostModel {
+
+  // optimistic default of 2x acceleration
+  private val defaultAcceleration = 2.0
+
+  override def estimateCost(plan: SparkPlan): CometCostEstimate = {
+    // Walk the entire plan tree and accumulate costs
+    var totalAcceleration = 0.0
+    var operatorCount = 0
+
+    def collectOperatorCosts(node: SparkPlan): Unit = {
+      val operatorCost = estimateOperatorCost(node)
+      totalAcceleration += operatorCost.acceleration
+      operatorCount += 1
+
+      // Recursively process children
+      node.children.foreach(collectOperatorCosts)

Review Comment:
   Perhaps we could remove usage of vars and let the function return the totalAcceleration and operator count itself ? 
   
   Something like : 
   ```
   def countItems(list: List[Any], accumulator: Int = 0): Int = {
     list match {
       case head :: tail => countItems(tail, accumulator + 1)
       case Nil => accumulator
     }
   }
   
   val myList = List(1, 2, 3, 4)
   val count = countItems(myList)  // result: 4
   ```



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Re: [PR] feat: Proof-of-concept of cost-based optimization [WIP / Experimental] [datafusion-comet]

Posted by "andygrove (via GitHub)" <gi...@apache.org>.
andygrove commented on code in PR #2906:
URL: https://github.com/apache/datafusion-comet/pull/2906#discussion_r2621037810


##########
spark/src/main/scala/org/apache/comet/cost/CometCostModel.scala:
##########
@@ -0,0 +1,103 @@
+/*
+ * 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.comet.cost
+
+import org.apache.spark.sql.catalyst.expressions.{BinaryArithmetic, Expression}
+import org.apache.spark.sql.comet.{CometColumnarToRowExec, CometPlan, CometProjectExec}
+import org.apache.spark.sql.comet.execution.shuffle.{CometColumnarShuffle, CometNativeShuffle, CometShuffleExchangeExec}
+import org.apache.spark.sql.execution.SparkPlan
+
+import org.apache.comet.DataTypeSupport
+
+case class CometCostEstimate(acceleration: Double)
+
+trait CometCostModel {
+
+  /** Estimate the relative cost of one operator */
+  def estimateCost(plan: SparkPlan): CometCostEstimate
+}
+
+class DefaultCometCostModel extends CometCostModel {
+
+  // optimistic default of 2x acceleration
+  private val defaultAcceleration = 2.0
+
+  override def estimateCost(plan: SparkPlan): CometCostEstimate = {
+    // Walk the entire plan tree and accumulate costs
+    var totalAcceleration = 0.0
+    var operatorCount = 0
+
+    def collectOperatorCosts(node: SparkPlan): Unit = {
+      val operatorCost = estimateOperatorCost(node)
+      totalAcceleration += operatorCost.acceleration
+      operatorCount += 1
+
+      // Recursively process children
+      node.children.foreach(collectOperatorCosts)

Review Comment:
   I don't know how much of this code will still exist by the time the proof-of-concept is working and ready for detailed code review, so I'll hold off from making these changes now. 
   
   I am really looking for high-level feedback on the general approach at the moment.



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Re: [PR] feat: Proof-of-concept of cost-based optimization [WIP / Experimental] [datafusion-comet]

Posted by "andygrove (via GitHub)" <gi...@apache.org>.
andygrove closed pull request #2906: feat: Proof-of-concept of cost-based optimization [WIP / Experimental]
URL: https://github.com/apache/datafusion-comet/pull/2906


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Re: [PR] feat: Proof-of-concept of AQE cost-based optimization [datafusion-comet]

Posted by "codecov-commenter (via GitHub)" <gi...@apache.org>.
codecov-commenter commented on PR #2906:
URL: https://github.com/apache/datafusion-comet/pull/2906#issuecomment-3651848288

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   <details><summary>Additional details and impacted files</summary>
   
   
   
   ```diff
   @@              Coverage Diff              @@
   ##               main    #2906       +/-   ##
   =============================================
   - Coverage     56.12%   10.08%   -46.05%     
   + Complexity      976      234      -742     
   =============================================
     Files           119      169       +50     
     Lines         11743    15384     +3641     
     Branches       2251     2532      +281     
   =============================================
   - Hits           6591     1551     -5040     
   - Misses         4012    13657     +9645     
   + Partials       1140      176      -964     
   ```
   </details>
   
   [:umbrella: View full report in Codecov by Sentry](https://app.codecov.io/gh/apache/datafusion-comet/pull/2906?dropdown=coverage&src=pr&el=continue&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache).   
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Re: [PR] feat: Proof-of-concept of AQE cost-based optimization [datafusion-comet]

Posted by "andygrove (via GitHub)" <gi...@apache.org>.
andygrove commented on PR #2906:
URL: https://github.com/apache/datafusion-comet/pull/2906#issuecomment-3651802026

   @mbutrovich I expect that you may have some opinions on this one!


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