cloud-fan commented on a change in pull request #28996:
URL: https://github.com/apache/spark/pull/28996#discussion_r450162816
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
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@@ -2656,6 +2656,14 @@ object SQLConf {
.checkValue(_ > 0, "The difference must be positive.")
.createWithDefault(4)
+ val ALLOW_MISSING_COLUMNS_IN_UNION_BY_NAME =
+ buildConf("spark.sql.allowMissingColumnsInUnionByName")
+ .doc("If this config is enabled, `Dataset.unionByName` allows different
set of column names " +
+ "between two Datasets. Missing columns at each side, will be filled with
null values.")
Review comment:
It seems not a breaking change if this case fails before and now we
allow it by filling missing columns with nulls. Do we really need a config? cc
@gatorsmile @bart-samwel
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