Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/17152#discussion_r104743057
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/views.scala ---
@@ -358,4 +366,51 @@ object ViewHelper {
generateViewDefaultDatabase(viewDefaultDatabase) ++
generateQueryColumnNames(queryOutput)
}
+
+ /**
+ * Recursively search the logical plan to detect cyclic view references,
throw an
+ * AnalysisException if cycle detected.
+ *
+ * A cyclic view reference is a cycle of reference dependencies, for
example, if the following
+ * statements are executed:
+ * CREATE VIEW testView AS SELECT id FROM tbl
+ * CREATE VIEW testView2 AS SELECT id FROM testView
+ * ALTER VIEW testView AS SELECT * FROM testView2
+ * The view `testView` references `testView2`, and `testView2` also
references `testView`,
+ * therefore a reference cycle (testView -> testView2 -> testView)
exists.
+ *
+ * @param plan the logical plan we detect cyclic view references from.
+ * @param path the path between the altered view and current node.
+ * @param viewIdent the table identifier of the altered view, we compare
two views by the
+ * `desc.identifier`.
+ */
+ def checkCyclicViewReference(
+ plan: LogicalPlan,
+ path: Seq[TableIdentifier],
+ viewIdent: TableIdentifier): Unit = {
+ plan match {
+ case v: View =>
+ val ident = v.desc.identifier
+ val newPath = path :+ ident
+ // If the table identifier equals to the `viewIdent`, current view
node is the same with
+ // the altered view. We detect a view reference cycle, should
throw an AnalysisException.
+ if (ident == viewIdent) {
+ throw new AnalysisException(s"Recursive view $viewIdent detected
" +
+ s"(cycle: ${newPath.mkString(" -> ")})")
+ } else {
+ v.children.foreach { child =>
+ checkCyclicViewReference(child, newPath, viewIdent)
+ }
+ }
+ case _ =>
+ plan.children.foreach(child => checkCyclicViewReference(child,
path, viewIdent))
+ }
+
+ // Detect cyclic references from subqueries.
+ plan.expressions.foreach { expr =>
+ if (expr.isInstanceOf[SubqueryExpression]) {
+
checkCyclicViewReference(expr.asInstanceOf[SubqueryExpression].plan, path,
viewIdent)
--- End diff --
+1
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