Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/15717#discussion_r92117267
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/ddl.scala ---
@@ -274,6 +274,76 @@ case class AlterTableUnsetPropertiesCommand(
}
+
+/**
+ * A command to change the columns for a table, only support changing the
comments of non-partition
+ * columns for now.
+ *
+ * The syntax of using this command in SQL is:
+ * {{{
+ * ALTER TABLE table_identifier
+ * CHANGE [COLUMN] column_old_name column_new_name column_dataType
[COMMENT column_comment]
+ * [FIRST | AFTER column_name];
+ * }}}
+ */
+case class AlterTableChangeColumnsCommand(
+ tableName: TableIdentifier,
+ columns: Map[String, StructField]) extends RunnableCommand {
+
+ // TODO: support change column name/dataType/metadata/position.
+ override def run(sparkSession: SparkSession): Seq[Row] = {
+ val catalog = sparkSession.sessionState.catalog
+ val table = catalog.getTableMetadata(tableName)
+ val resolver = sparkSession.sessionState.conf.resolver
+ DDLUtils.verifyAlterTableType(catalog, table, isView = false)
+
+ // Create a map that converts the origin column to the new column with
changed comment, throw
+ // a Exception if the column reference is invalid or the column
name/dataType is changed.
+ val columnsMap = columns.map { case (oldName: String, newField:
StructField) =>
+ // Find the origin column from schema by column name.
+ val originColumn = findColumn(table.schema, oldName, resolver)
+ // Throw a Exception if the column name/dataType is changed.
--- End diff --
Nit: please correct `a Exception` to `an exception` in all the comments you
added. Thanks!
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