Github user xuanyuanking commented on a diff in the pull request: https://github.com/apache/spark/pull/19773#discussion_r151990044 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/command/ddl.scala --- @@ -318,16 +318,28 @@ case class AlterTableChangeColumnCommand( s"'${newColumn.name}' with type '${newColumn.dataType}'") } + val changeSchema = originColumn.dataType != newColumn.dataType val newSchema = table.schema.fields.map { field => if (field.name == originColumn.name) { - // Create a new column from the origin column with the new comment. - addComment(field, newColumn.getComment) + var newField = field --- End diff -- More clear for getting rid of var, pls check next patch. If we implement rename or others meta change feature here, may still need some code rework.
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