Github user andrewor14 commented on a diff in the pull request:
https://github.com/apache/spark/pull/12222#discussion_r59631726
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/commands.scala
---
@@ -423,6 +424,100 @@ case class ShowTablePropertiesCommand(
}
/**
+ * A command for users to list the column names for a table. This function
creates a
+ * [[ShowColumnsCommand]] logical plan.
+ *
+ * The syntax of using this command in SQL is:
+ * {{{
+ * SHOW COLUMNS (FROM | IN) table_identifier [(FROM | IN) database];
+ * }}}
+ */
+case class ShowColumnsCommand(table: TableIdentifier) extends
RunnableCommand {
+ // The result of SHOW COLUMNS has one column called 'result'
+ override val output: Seq[Attribute] = {
+ AttributeReference("result", StringType, nullable = false)() :: Nil
+ }
+
+ override def run(sqlContext: SQLContext): Seq[Row] = {
+ val relation = sqlContext.sessionState.catalog.lookupRelation(table,
None)
+ relation.schema.fields.map { field =>
+ Row(field.name)
+ }
+ }
+}
+
+/**
+ * A command for users to list the partition names of a table. If the
partition spec is specified,
+ * partitions that match the spec are returned. [[AnalysisException]]
exception is thrown under
+ * the following conditions:
+ *
+ * 1. If the command is called for a non partitioned table.
+ * 2. If the partition spec refers to the columns that are not defined as
partitioning columns.
+ *
+ * This function creates a [[ShowPartitionsCommand]] logical plan
+ *
+ * The syntax of using this command in SQL is:
+ * {{{
+ * SHOW PARTITIONS [db_name.]table_name [PARTITION(partition_spec)]
+ * }}}
+ */
+case class ShowPartitionsCommand(
+ table: TableIdentifier,
+ partitionSpec: Option[Map[String, String]]) extends RunnableCommand {
--- End diff --
please use `ExternalCatalog.TablePartitionSpec` here
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