viirya commented on a change in pull request #29812:
URL: https://github.com/apache/spark/pull/29812#discussion_r493111576
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/WithFields.scala
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@@ -17,16 +17,29 @@
package org.apache.spark.sql.catalyst.optimizer
-import org.apache.spark.sql.catalyst.expressions.WithFields
+import scala.collection.mutable
+
+import org.apache.spark.sql.catalyst.expressions.{Expression, GetStructField,
WithFields}
import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
import org.apache.spark.sql.catalyst.rules.Rule
/**
- * Combines all adjacent [[WithFields]] expression into a single
[[WithFields]] expression.
+ * Optimizes [[WithFields]] expression chains.
*/
-object CombineWithFields extends Rule[LogicalPlan] {
+object OptimizeWithFields extends Rule[LogicalPlan] {
def apply(plan: LogicalPlan): LogicalPlan = plan transformAllExpressions {
+ case WithFields(structExpr, names, values) if names.distinct.length !=
names.length =>
+ val newNames = mutable.ArrayBuffer.empty[String]
+ val newValues = mutable.ArrayBuffer.empty[Expression]
+ names.zip(values).reverse.foreach { case (name, value) =>
+ if (!newNames.contains(name)) {
+ newNames += name
+ newValues += value
+ }
+ }
+ WithFields(structExpr, names = newNames.reverse.toSeq, valExprs =
newValues.reverse.toSeq)
Review comment:
Actually I'd like to run these rules to simplify `WithFields` tree early
in analysis stage. After #29587, I thought that it is very likely to write bad
`WithFields` tree. Once hitting that, it is very hard to debug and the
analyzer/optimizer spend a lot of time traversing expression tree. So I think
it is very useful keep this rule to simplify the expression tree, but I don't
think we want to do `ReplaceWithFieldsExpression` in analysis stage.
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