allisonwang-db commented on a change in pull request #32303:
URL: https://github.com/apache/spark/pull/32303#discussion_r620004435
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/unresolved.scala
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@@ -392,16 +392,27 @@ case class UnresolvedStar(target: Option[Seq[String]])
extends Star with Unevalu
throw
QueryCompilationErrors.starExpandDataTypeNotSupportedError(target.get)
}
} else {
- val from = input.inputSet.map(_.name).mkString(", ")
- val targetString = target.get.mkString(".")
- throw
QueryCompilationErrors.cannotResolveStarExpandGivenInputColumnsError(
- targetString, from)
+ // Change the unresolved star to an expanded star to indicate the star
has been
+ // expanded once.
+ ExpandedStar(this) :: Nil
}
}
override def toString: String = target.map(_ + ".").getOrElse("") + "*"
}
+/**
+ * Represent an [[UnresolvedStar]] that has been to expand once.
+ * This can be used to resolve a star expression using multiple plans.
+ */
+case class ExpandedStar(star: UnresolvedStar) extends Star with Unevaluable {
Review comment:
This is used to differenate between an unresolved star and a star that
has been tried to resolved once. It's intended to keep the error message
consistent when the star usage is invalid in an expression. But indeed this is
confusing and I will think of other ways to check the invalid usage.
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