mgaido91 commented on a change in pull request #23531: [SPARK-24497][SQL]
Support recursive SQL query
URL: https://github.com/apache/spark/pull/23531#discussion_r248288430
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
##########
@@ -205,30 +206,145 @@ class Analyzer(
CleanupAliases)
)
+ object ResolveRecursiveReferneces extends Rule[LogicalPlan] {
+ def apply(plan: LogicalPlan): LogicalPlan = {
+ val recursiveTables = plan.collect {
+ case rt @ RecursiveTable(name, _, _) if rt.anchorResolved => name -> rt
+ }.toMap
+
+ plan.resolveOperatorsUp {
+ case UnresolvedRecursiveReference(name) if
recursiveTables.contains(name) =>
+ RecursiveReference(name,
recursiveTables(name).output.map(_.newInstance()))
+ case other => other
+ }
+ }
+ }
+
/**
* Analyze cte definitions and substitute child plan with analyzed cte
definitions.
*/
object CTESubstitution extends Rule[LogicalPlan] {
def apply(plan: LogicalPlan): LogicalPlan = plan.resolveOperatorsUp {
- case With(child, relations) =>
+ case With(child, relations, allowRecursion) =>
substituteCTE(child, relations.foldLeft(Seq.empty[(String,
LogicalPlan)]) {
case (resolved, (name, relation)) =>
- resolved :+ name -> executeSameContext(substituteCTE(relation,
resolved))
- })
+ val recursiveTableName = if (allowRecursion) Some(name) else None
+ resolved :+
+ name -> executeSameContext(substituteCTE(relation, resolved,
recursiveTableName))
+ }, None)
case other => other
}
- def substituteCTE(plan: LogicalPlan, cteRelations: Seq[(String,
LogicalPlan)]): LogicalPlan = {
- plan resolveOperatorsDown {
- case u: UnresolvedRelation =>
- cteRelations.find(x => resolver(x._1, u.tableIdentifier.table))
- .map(_._2).getOrElse(u)
- case other =>
- // This cannot be done in ResolveSubquery because ResolveSubquery
does not know the CTE.
- other transformExpressions {
- case e: SubqueryExpression =>
- e.withNewPlan(substituteCTE(e.plan, cteRelations))
+ def substituteCTE(
+ plan: LogicalPlan,
+ cteRelations: Seq[(String, LogicalPlan)],
+ recursiveTableName: Option[String]): LogicalPlan = {
+ def substitute(
+ plan: LogicalPlan,
+ inSubQuery: Boolean = false): (LogicalPlan, Boolean) = {
+ val references = mutable.Set.empty[UnresolvedRecursiveReference]
+
+ def newReference(recursiveTableName: String) = {
+ val recursiveReference =
UnresolvedRecursiveReference(recursiveTableName)
+ references += recursiveReference
+
+ recursiveReference
+ }
+
+ val newPlan = plan resolveOperatorsDown {
+ case u: UnresolvedRelation =>
+ val table = u.tableIdentifier.table
+
+ val recursiveReference = recursiveTableName.find(resolver(_,
table)).map { name =>
+ if (inSubQuery) {
+ throw new AnalysisException(
+ s"Recursive reference ${name} can't be used in a subquery")
+ }
+
+ newReference(name)
+ }
+
+ recursiveReference
+ .orElse(cteRelations.find(x => resolver(x._1, table)).map(_._2))
+ .getOrElse(u)
+
+ case other =>
+ // This cannot be done in ResolveSubquery because ResolveSubquery
does not know the CTE.
+ other transformExpressions {
+ case e: SubqueryExpression => e.withNewPlan(substitute(e.plan,
true)._1)
+ }
+ }
+
+ (newPlan, !references.isEmpty)
+ }
+
+ plan match {
+ case SubqueryAlias(name, u: Union) if recursiveTableName.isDefined =>
+ def combineUnions(union: Union): Seq[LogicalPlan] =
union.children.flatMap {
+ case u: Union => combineUnions(u)
+ case o => Seq(o)
}
+
+ val substitutedTerms = combineUnions(u).map(substitute(_))
+ val (anchorTerms, recursiveTerms) = substitutedTerms.partition(!_._2)
+
+ if (!recursiveTerms.isEmpty) {
+ if (anchorTerms.isEmpty) {
+ throw new AnalysisException("There should be at least 1 anchor
term defined in a " +
+ s"recursive query $name")
+ }
+
+ val recursiveTermPlans = recursiveTerms.map(_._1)
+
+ def traversePlanAndCheck(
+ plan: LogicalPlan,
+ isRecursiveReferenceAllowed: Boolean = true): Boolean = plan
match {
+ case UnresolvedRecursiveReference(name) =>
+ if (!isRecursiveReferenceAllowed) {
+ throw new AnalysisException(s"Wrong usage of recursive
reference ${name}")
Review comment:
I think we can have a trade-off here. I mean we can say something like:
```
Recursive reference ... cannot be used here. This can be caused by using it
on the right side of a left-outer join or ...
```
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
With regards,
Apache Git Services
---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org
For additional commands, e-mail: reviews-h...@spark.apache.org
