milanisvet commented on code in PR #49518:
URL: https://github.com/apache/spark/pull/49518#discussion_r1917917583
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/CheckAnalysis.scala:
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@@ -1042,6 +1043,75 @@ trait CheckAnalysis extends PredicateHelper with
LookupCatalog with QueryErrorsB
if (Utils.isTesting) scrubOutIds(result) else result
}
+ /**
+ * Recursion, according to SQL standard, comes with several limitations:
+ * 1. Recursive term can contain one recursive reference only.
+ * 2. Recursive reference can't be used in some kinds of joins and
aggregations.
+ * This rule checks that these restrictions are not violated.
+ */
+ private def checkRecursion(
+ plan: LogicalPlan,
+ references: mutable.Map[Long, (Int, Seq[DataType])] =
mutable.Map.empty): Unit = {
+ plan match {
+ // The map is filled with UnionLoop id as key and 0 (number of Ref
occasions) and datatype
+ // as value
+ case UnionLoop(id, anchor, recursion, _) =>
+ checkRecursion(anchor, references)
Review Comment:
`anchor` plan can't contain recursive references, but we also need to enter
it to really confirm that.
Here we are entering it with the `references` map which does not contain
current id, so if we encounter a self-references there, it will throw an error.
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