maropu commented on a change in pull request #29587:
URL: https://github.com/apache/spark/pull/29587#discussion_r480085360
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveUnion.scala
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@@ -17,29 +17,97 @@
package org.apache.spark.sql.catalyst.analysis
+import scala.collection.mutable
+
import org.apache.spark.sql.AnalysisException
-import org.apache.spark.sql.catalyst.expressions.{Alias, Literal}
+import org.apache.spark.sql.catalyst.expressions.{Alias, Attribute,
Expression, Literal, NamedExpression, WithFields}
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._
import org.apache.spark.sql.util.SchemaUtils
/**
* Resolves different children of Union to a common set of columns.
*/
object ResolveUnion extends Rule[LogicalPlan] {
- private def unionTwoSides(
+ /**
+ * Adds missing fields recursively into given `col` expression, based on the
target `StructType`.
+ * For example, given `col` as "a struct<a:int, b:int>, b int" and `target`
as
+ * "a struct<a:int, b:int, c: long>, b int, c string", this method should
add `a.c` and `c` to
+ * `col` expression.
+ */
+ private def addFields(col: NamedExpression, target: StructType):
Option[Expression] = {
+ require(col.dataType.isInstanceOf[StructType], "Only support StructType.")
+
+ val resolver = SQLConf.get.resolver
+ val missingFields =
+ StructType.findMissingFields(col.dataType.asInstanceOf[StructType],
target, resolver)
+ if (missingFields.length == 0) {
+ None
+ } else {
+ Some(addFieldsInto(col, "", missingFields.fields))
+ }
+ }
+
+ private def addFieldsInto(col: Expression, base: String, fields:
Seq[StructField]): Expression = {
+ var currCol = col
+ fields.foreach { field =>
+ field.dataType match {
+ case dt: AtomicType =>
+ // We need to sort columns in result, because we might add another
column in other side.
+ // E.g., we want to union two structs "a int, b long" and "a int, c
string".
+ // If we don't sort, we will have "a int, b long, c string" and "a
int, c string, b long",
+ // which are not compatible.
Review comment:
To avoid the issue described here, we cannot just sort input columns
instead of adding.a new filed `sortColumns` in `WithFields`?
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