huaxingao commented on a change in pull request #30473:
URL: https://github.com/apache/spark/pull/30473#discussion_r532990800
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/jdbc/JDBCTableCatalog.scala
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@@ -170,6 +174,125 @@ class JDBCTableCatalog extends TableCatalog with Logging {
}
}
+ override def namespaceExists(namespace: Array[String]): Boolean = namespace
match {
+ case Array(db) =>
+ listNamespaces.exists (_(0) == db)
Review comment:
You mean it's expensive to fetch namespaces info from the underlying
databases, right? We can't save the previously fetched info and reuse it,
because somebody else might have created or dropped namespaces after the last
fetch. I guess we have to fetch again every time we need the info?
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