imback82 commented on a change in pull request #30881:
URL: https://github.com/apache/spark/pull/30881#discussion_r548272691
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/v2Commands.scala
##########
@@ -344,10 +344,11 @@ case class DescribeRelation(
*/
case class DescribeColumn(
relation: LogicalPlan,
- colNameParts: Seq[String],
+ column: NamedExpression,
isExtended: Boolean) extends Command {
override def children: Seq[LogicalPlan] = Seq(relation)
override def output: Seq[Attribute] =
DescribeCommandSchema.describeColumnAttributes()
+ override lazy val references: AttributeSet = AttributeSet.empty
Review comment:
This is one possible implementation of `inputSet` here:
```scala
override lazy val inputSet: AttributeSet = {
val output = relation match {
case r: ResolvedTable => r.table.schema.toAttributes // creates new
AttributeReference
case _ => Seq() // should assert
}
AttributeSet(output)
}
```
However, when `DescribeColumn` case class is copied in `ResolveAttribute`
(`r.copy(column = resolvedCol)`), new `AttributeReference`s are created since
`toAttributes` is called.
Any idea on the workaround (without updating `ResolvedTable` to have
`output`)?
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