Github user xuanyuanking commented on a diff in the pull request:
https://github.com/apache/spark/pull/19773#discussion_r216127880
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/ddl.scala ---
@@ -350,16 +366,11 @@ case class AlterTableChangeColumnCommand(
s"${schema.fieldNames.mkString("[`", "`, `", "`]")}"))
}
- // Add the comment to a column, if comment is empty, return the original
column.
- private def addComment(column: StructField, comment: Option[String]):
StructField = {
- comment.map(column.withComment(_)).getOrElse(column)
- }
-
--- End diff --
Thanks for the checking, my mistake of not describe the intention to do
this feature. We want support type change just want to add the ability of
changing the metadata of column type. The scenario we meet is our user want a
type change(like int is not enough, need a long type), they has done the type
changing in their data file, but we should hack to change the metastore or
create the whole table again.
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