[GitHub] [spark] HyukjinKwon commented on a change in pull request #29812: [SPARK-32941][SQL] Optimize UpdateFields expression chain and put the rule early in Analysis phase

[GitBox <gi...@apache.org>]

HyukjinKwon commented on a change in pull request #29812:
URL: https://github.com/apache/spark/pull/29812#discussion_r508195964



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/UpdateFields.scala
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@@ -17,19 +17,68 @@
 
 package org.apache.spark.sql.catalyst.optimizer
 
-import org.apache.spark.sql.catalyst.expressions.UpdateFields
+import java.util.Locale
+
+import scala.collection.mutable
+
+import org.apache.spark.sql.catalyst.expressions.{Expression, UpdateFields, WithField}
 import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
 import org.apache.spark.sql.catalyst.rules.Rule
+import org.apache.spark.sql.internal.SQLConf
 
 
 /**
- * Combines all adjacent [[UpdateFields]] expression into a single [[UpdateFields]] expression.
+ * Optimizes [[UpdateFields]] expression chains.
  */
-object CombineUpdateFields extends Rule[LogicalPlan] {
-  def apply(plan: LogicalPlan): LogicalPlan = plan transformAllExpressions {
+object OptimizeUpdateFields extends Rule[LogicalPlan] {
+  private def canOptimize(names: Seq[String]): Boolean = {
+    if (SQLConf.get.caseSensitiveAnalysis) {
+      names.distinct.length != names.length
+    } else {
+      names.map(_.toLowerCase(Locale.ROOT)).distinct.length != names.length
+    }
+  }
+
+  val optimizeUpdateFields: PartialFunction[Expression, Expression] = {
+    case UpdateFields(structExpr, fieldOps)
+      if fieldOps.forall(_.isInstanceOf[WithField]) &&
+        canOptimize(fieldOps.map(_.asInstanceOf[WithField].name)) =>
+      val caseSensitive = SQLConf.get.caseSensitiveAnalysis
+
+      val withFields = fieldOps.map(_.asInstanceOf[WithField])
+      val names = withFields.map(_.name)
+      val values = withFields.map(_.valExpr)
+
+      val newNames = mutable.ArrayBuffer.empty[String]
+      val newValues = mutable.ArrayBuffer.empty[Expression]
+
+      if (caseSensitive) {
+        names.zip(values).reverse.foreach { case (name, value) =>

Review comment:
       I wonder if we could just do like: `collection.immutable.ListMap(names.zip(values): _*)` which will keep the last win here and keep the order of fields to use later. But I guess it's no big deal. Just saying.




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