cloud-fan commented on a change in pull request #23883: [SPARK-26982][SQL]
Enhance describe framework to describe the output of a query.
URL: https://github.com/apache/spark/pull/23883#discussion_r260712769
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/tables.scala
##########
@@ -617,10 +617,55 @@ case class DescribeTableCommand(
}
private def append(
- buffer: ArrayBuffer[Row], column: String, dataType: String, comment:
String): Unit = {
+ buffer: ArrayBuffer[Row], column: String, dataType: String, comment:
String): Unit = {
buffer += Row(column, dataType, comment)
}
}
+/**
+ * Command can of the following form.
+ * {{{
+ * DESCRIBE [EXTENDED|FORMATTED] table_name partitionSpec?;
+ * }}}
+ */
+case class DescribeTableCommand(
+ tableIdent: TableIdentifier,
+ partitionSpec: TablePartitionSpec,
+ isExtended: Boolean)
+ extends DescribeTableCommandBase {
+
+ override def run(sparkSession: SparkSession): Seq[Row] = {
+ val result = new ArrayBuffer[Row]
+ describeTable(sparkSession, tableIdent, partitionSpec, isExtended, result)
+ result
+ }
+}
+
+/**
+ * Command can of the following form.
+ * {{{
+ * DESCRIBE [QUERY] query_statement
+ * }}}
+ */
+case class DescribeQueryCommand(query: LogicalPlan)
+ extends DescribeTableCommandBase {
+
+ override def run(sparkSession: SparkSession): Seq[Row] = {
+ val result = new ArrayBuffer[Row]
+ query match {
+ case p if p.collectFirst { case _: InsertIntoTable | _: InsertIntoDir =>
true }.isDefined =>
+ throw new AnalysisException("Describe command is not supported for
insert statements.")
Review comment:
I don't have a strong preference here, but the DB2 does this in the parser,
I'm wondering if we should do this in the parser as well.
instead of `(DESC | DESCRIBE) QUERY? query`, how about `(DESC | DESCRIBE)
QUERY? querySpecification`?
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