Github user dilipbiswal commented on a diff in the pull request:
https://github.com/apache/spark/pull/12222#discussion_r59687345
--- 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 {
+ // The result of SHOW PARTITIONS has one column called 'result'
+ override val output: Seq[Attribute] = {
+ AttributeReference("result", StringType, nullable = false)() :: Nil
+ }
+
+ /**
+ * This function validates the partitioning spec by making sure all the
referenced columns are
+ * defined as partitioning columns in table definition. An
AnalysisException exception is
+ * thrown if the partitioning spec is invalid.
+ */
+ private def validatePartitionSpec(table: CatalogTable, spec: Map[String,
String]): Unit = {
+ if (!spec.keySet.forall(table.partitionColumns.map(_.name).contains)) {
+ throw new AnalysisException(s"Partition spec ${spec.mkString("(", ",
", ")")} contains " +
+ s"non-partition columns")
+ }
+ }
+
+ /**
+ * Validates and throws an [[AnalysisException]] exception under the
following conditions:
+ * 1. If the table is not partitioned.
+ * 2. If it is a datasource table.
+ * 3. If it is a view or index table.
+ */
+ private def checkRequirements(table: CatalogTable): Unit = {
+ if (table.tableType == CatalogTableType.VIRTUAL_VIEW ||
+ table.tableType == CatalogTableType.INDEX_TABLE) {
+ throw new AnalysisException("Operation not allowed: view or index
table")
+ } else if (!DDLUtils.isTablePartitioned(table)) {
+ throw new AnalysisException(s"Table ${table.qualifiedName} is not a
partitioned table")
+ } else if (DDLUtils.isDatasourceTable(table)) {
+ throw new AnalysisException("Operation not allowed: datasource
table")
--- End diff --
Will make the change
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