prakharjain09 commented on a change in pull request #30300:
URL: https://github.com/apache/spark/pull/30300#discussion_r521211539
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File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/AliasAwareOutputExpression.scala
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@@ -25,20 +25,14 @@ import
org.apache.spark.sql.catalyst.plans.physical.{HashPartitioning, Partition
trait AliasAwareOutputExpression extends UnaryExecNode {
protected def outputExpressions: Seq[NamedExpression]
- protected def hasAlias: Boolean = outputExpressions.collectFirst { case _:
Alias => }.isDefined
+ lazy val aliasMap = AttributeMap(outputExpressions.collect {
+ case a @ Alias(child: AttributeReference, _) => (child, a.toAttribute)
+ })
- protected def replaceAliases(exprs: Seq[Expression]): Seq[Expression] = {
- exprs.map {
- case a: AttributeReference => replaceAlias(a).getOrElse(a)
- case other => other
- }
- }
+ protected def hasAlias: Boolean = aliasMap.nonEmpty
protected def replaceAlias(attr: AttributeReference): Option[Attribute] = {
Review comment:
I looked into AliasHelper - it has utility methods to pushdown
expressions. i.e. suppose we have f1 filter on top of Project, how to transform
f1 so that we can use it below Project. For this it creates mapping between
newName -> oldExpression.
In our case, we want different kind of map. given an expression coming from
below the project, how will it look above Project. For this we need
oldAttributeReference -> newAttributeReference map.
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