Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/16233#discussion_r94682588
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -510,32 +539,93 @@ class Analyzer(
* Replaces [[UnresolvedRelation]]s with concrete relations from the
catalog.
*/
object ResolveRelations extends Rule[LogicalPlan] {
- private def lookupTableFromCatalog(u: UnresolvedRelation): LogicalPlan
= {
+
+ // If the unresolved relation is running directly on files, we just
return the original
+ // UnresolvedRelation, the plan will get resolved later. Else we look
up the table from catalog
+ // and change the default database name if it is a view.
+ // We usually look up a table from the default database if the table
identifier has an empty
+ // database part, for a view the default database should be the
currentDb when the view was
+ // created. When the case comes to resolving a nested view, the view
may have different default
+ // database with that the referenced view has, so we need to use the
variable `defaultDatabase`
+ // to track the current default database.
+ // When the relation we resolve is a view, we fetch the
view.desc(which is a CatalogTable), and
+ // then set the value of `CatalogTable.viewDefaultDatabase` to the
variable `defaultDatabase`,
+ // we look up the relations that the view references using the default
database.
+ // For example:
+ // |- view1 (defaultDatabase = db1)
+ // |- operator
+ // |- table2 (defaultDatabase = db1)
+ // |- view2 (defaultDatabase = db2)
+ // |- view3 (defaultDatabase = db3)
+ // |- view4 (defaultDatabase = db4)
+ // In this case, the view `view1` is a nested view, it directly
references `table2`ã`view2`
+ // and `view4`, the view `view2` references `view3`. On resolving the
table, we look up the
+ // relations `table2`ã`view2`ã`view4` using the default database
`db1`, and look up the
+ // relation `view3` using the default database `db2`.
+ //
+ // Note this is compatible with the views defined by older versions of
Spark(before 2.2), which
+ // have empty defaultDatabase and all the relations in viewText have
database part defined.
+ def resolveRelation(
+ plan: LogicalPlan,
+ defaultDatabase: Option[String] = None): LogicalPlan = plan match {
+ case u @ UnresolvedRelation(table: TableIdentifier, _) if
isRunningDirectlyOnFiles(table) =>
+ u
+ case u: UnresolvedRelation =>
+ val defaultDatabase = AnalysisContext.get.defaultDatabase
+ val relation = lookupTableFromCatalog(u, defaultDatabase)
+ resolveRelation(relation, defaultDatabase)
+ // Hive support is required to resolve a persistent view, the
logical plan returned by
+ // catalog.lookupRelation() should be:
+ // `SubqueryAlias(_, View(desc: CatalogTable, desc.output, child:
LogicalPlan), _)`,
+ // where the child should be a logical plan parsed from
`desc.viewText`.
+ // If the child of a view is empty, we will throw an
AnalysisException later in
+ // `checkAnalysis`.
+ case view @ View(desc, _, Some(child)) =>
+ val context = AnalysisContext(defaultDatabase =
desc.viewDefaultDatabase)
--- End diff --
Also set the nestedViewLevel?
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