Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/16422#discussion_r122348016
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/tables.scala ---
@@ -619,6 +620,104 @@ case class DescribeTableCommand(
}
}
+/**
+ * A command to list the info for a column, including name, data type,
column stats and comment.
+ * This function creates a [[DescribeColumnCommand]] logical plan.
+ *
+ * The syntax of using this command in SQL is:
+ * {{{
+ * DESCRIBE [EXTENDED|FORMATTED] table_name column_name;
+ * }}}
+ */
+case class DescribeColumnCommand(
+ table: TableIdentifier,
+ column: String,
+ isFormatted: Boolean)
+ extends RunnableCommand {
+
+ override val output: Seq[Attribute] = {
+ // The displayed names are based on Hive.
+ // (Link for the corresponding Hive Jira:
https://issues.apache.org/jira/browse/HIVE-7050)
+ if (isFormatted) {
+ Seq(
+ AttributeReference("col_name", StringType, nullable = false,
+ new MetadataBuilder().putString("comment", "name of the
column").build())(),
+ AttributeReference("data_type", StringType, nullable = false,
+ new MetadataBuilder().putString("comment", "data type of the
column").build())(),
+ AttributeReference("min", StringType, nullable = true,
+ new MetadataBuilder().putString("comment", "min value of the
column").build())(),
+ AttributeReference("max", StringType, nullable = true,
--- End diff --
shall we use the actual column type?
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