mgaido91 commented on a change in pull request #23285: [SPARK-26224][SQL] Avoid
creating many project on subsequent calls to withColumn
URL: https://github.com/apache/spark/pull/23285#discussion_r240577269
##########
File path: sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
##########
@@ -2164,16 +2164,16 @@ class Dataset[T] private[sql](
columnMap.find { case (colName, _) =>
resolver(field.name, colName)
} match {
- case Some((colName: String, col: Column)) => col.as(colName)
- case _ => Column(field)
+ case Some((colName: String, col: Column)) => col.as(colName).named
+ case _ => field
}
}
- val newColumns = columnMap.filter { case (colName, col) =>
+ val newColumns = columnMap.filter { case (colName, _) =>
!output.exists(f => resolver(f.name, colName))
- }.map { case (colName, col) => col.as(colName) }
+ }.map { case (colName, col) => col.as(colName).named }
- select(replacedAndExistingColumns ++ newColumns : _*)
+ CollapseProject(Project(replacedAndExistingColumns ++ newColumns,
logicalPlan))
Review comment:
I don't think we can do that. Imagine the case when all the columns depend
on the previously added one: if we would do that, we would end up with an
invalid plan. Or am I missing something?
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