cloud-fan commented on code in PR #49351:
URL: https://github.com/apache/spark/pull/49351#discussion_r1917868339
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveWithCTE.scala:
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@@ -41,16 +47,113 @@ object ResolveWithCTE extends Rule[LogicalPlan] {
plan: LogicalPlan,
cteDefMap: mutable.HashMap[Long, CTERelationDef]): LogicalPlan = {
plan.resolveOperatorsDownWithPruning(_.containsAllPatterns(CTE)) {
- case w @ WithCTE(_, cteDefs) =>
- cteDefs.foreach { cteDef =>
- if (cteDef.resolved) {
- cteDefMap.put(cteDef.id, cteDef)
- }
+ case withCTE @ WithCTE(_, cteDefs) =>
+ val newCTEDefs = cteDefs.map {
+ // `cteDef.recursive` means "presence of a recursive CTERelationRef
under cteDef". The
+ // side effect of node substitution below is that after
CTERelationRef substitution
+ // its cteDef is no more considered `recursive`. This code path is
common for `cteDef`
+ // that were non-recursive from the get go, as well as those that
are no more recursive
+ // due to node substitution.
+ case cteDef if !cteDef.recursive =>
+ if (cteDef.resolved) {
+ cteDefMap.put(cteDef.id, cteDef)
+ }
+ cteDef
+ case cteDef =>
+ cteDef.child match {
+ // If it is a supported recursive CTE query pattern (4 so far),
extract the anchor and
+ // recursive plans from the Union and rewrite Union with
UnionLoop. The recursive CTE
+ // references inside UnionLoop's recursive plan will be
rewritten as UnionLoopRef,
+ // using the output of the resolved anchor plan. The side effect
of recursive
+ // CTERelationRef->UnionLoopRef substitution is that `cteDef`
that was originally
+ // considered `recursive` is no more in the context of
`cteDef.recursive` method
+ // definition.
+ //
+ // Simple case of duplicating (UNION ALL) clause.
+ case alias @ SubqueryAlias(_, Union(Seq(anchor, recursion),
false, false)) =>
+ if (!anchor.resolved) {
+ cteDef
+ } else {
+ val loop = UnionLoop(
+ cteDef.id,
+ anchor,
+ rewriteRecursiveCTERefs(recursion, anchor, cteDef.id,
None))
+ cteDef.copy(child = alias.copy(child = loop))
+ }
+
+ // The case of CTE name followed by a parenthesized list of
column name(s), eg.
+ // WITH RECURSIVE t(n).
+ case alias @ SubqueryAlias(_,
+ columnAlias @ UnresolvedSubqueryColumnAliases(
+ colNames,
+ Union(Seq(anchor, recursion), false, false)
+ )) =>
+ if (!anchor.resolved) {
+ cteDef
+ } else {
+ val loop = UnionLoop(
+ cteDef.id,
+ anchor,
+ rewriteRecursiveCTERefs(recursion, anchor, cteDef.id,
Some(colNames)))
+ cteDef.copy(child = alias.copy(child =
columnAlias.copy(child = loop)))
+ }
+
+ // If the recursion is described with an UNION (deduplicating)
clause then the
+ // recursive term should not return those rows that have been
calculated previously,
+ // and we exclude those rows from the current iteration result.
+ case alias @ SubqueryAlias(_,
+ Distinct(Union(Seq(anchor, recursion), false, false))) =>
Review Comment:
```suggestion
Distinct(Union(Seq(anchor, recursion), false, false))) =>
```
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