Peng-Lei commented on a change in pull request #33175:
URL: https://github.com/apache/spark/pull/33175#discussion_r664475325
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/v2Commands.scala
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@@ -662,6 +662,14 @@ case class ShowCurrentNamespace(catalogManager:
CatalogManager) extends LeafComm
AttributeReference("namespace", StringType, nullable = false)())
}
+/**
+ * The logical plan of the SHOW CATALOGS command.
+ */
+case class ShowCatalogs(catalogManager: CatalogManager) extends LeafCommand {
+ override val output: Seq[Attribute] = Seq(
+ AttributeReference("catalog", StringType, nullable = false)())
Review comment:
in big dataļ¼
1.[Presto](https://prestodb.io/docs/current/sql/show-catalogs.html), There
is no output information in the link, but actual output is just `name`
2.[Flink](https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/dev/table/sql/show/#run-a-show-statement).
in RDBMS
The catalog layer is not strictly implemented in RDS
1.In PG, Catalog(=database).Schema(namespace).Table, So `show catalogs` ==
`show databases`; Unfortunately, pg doesn't have this command. we should use
`select statement` instead of `show` command.
[difference-between-a-catalog-and-a-schema-in-a-relational-database](https://stackoverflow.com/questions/7022755/whats-the-difference-between-a-catalog-and-a-schema-in-a-relational-database)
2.In MySQL, There is no catalog, just schema(database).table. So we can
create a database use create schema/database xxx
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