maropu commented on a change in pull request #29585:
URL: https://github.com/apache/spark/pull/29585#discussion_r493977794
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveUnion.scala
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@@ -18,17 +18,34 @@
package org.apache.spark.sql.catalyst.analysis
import org.apache.spark.sql.AnalysisException
-import org.apache.spark.sql.catalyst.expressions.{Alias, Literal}
+import org.apache.spark.sql.catalyst.expressions.{Alias, Attribute,
AttributeReference, Literal, NamedExpression}
import org.apache.spark.sql.catalyst.optimizer.CombineUnions
import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, Project,
Union}
import org.apache.spark.sql.catalyst.rules.Rule
import org.apache.spark.sql.internal.SQLConf
+import org.apache.spark.sql.types.StructType
import org.apache.spark.sql.util.SchemaUtils
/**
* Resolves different children of Union to a common set of columns.
*/
object ResolveUnion extends Rule[LogicalPlan] {
+
+ private[catalyst] def makeUnionOutput(children: Seq[LogicalPlan]):
Seq[Attribute] = {
+ children.map(_.output).transpose.map { attrs =>
+ val firstAttr = attrs.head
+ val nullable = attrs.exists(_.nullable)
+ val newDt = attrs.map(_.dataType).reduce(StructType.merge)
+ val newExprId = NamedExpression.newExprId
+ if (firstAttr.dataType == newDt) {
+ firstAttr.withExprId(newExprId).withNullability(nullable)
Review comment:
NOTE: I've updated the code to assign new expr Ids in this case because
the `UpdateAttributeNullability` rule wrongly updates nullability in
`unionOutput` of `Union` if we reuse IDs here.
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