Github user liancheng commented on a diff in the pull request: https://github.com/apache/spark/pull/12222#discussion_r60927757 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/command/commands.scala --- @@ -423,6 +426,102 @@ 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] = { + sqlContext.sessionState.catalog.getTableMetadata(table).schema.map { c => + Row(c.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, + spec: Option[TablePartitionSpec]) extends RunnableCommand { + // The result of SHOW PARTITIONS has one column called 'result' + override val output: Seq[Attribute] = { + AttributeReference("result", StringType, nullable = false)() :: Nil + } + + def getPartName(spec: TablePartitionSpec): String = { + spec.map {s => + PartitioningUtils.escapePathName(s._1) + "=" + PartitioningUtils.escapePathName(s._2) + }.mkString("/") + } + override def run(sqlContext: SQLContext): Seq[Row] = { + val catalog = sqlContext.sessionState.catalog + val db = table.database.getOrElse(catalog.getCurrentDatabase) + if (catalog.isTemporaryTable(table)) { + throw new AnalysisException("SHOW PARTITIONS is not allowed on a temporary table: " + + s"${table.unquotedString}") --- End diff -- Wrong indentation here.
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