Github user davies commented on a diff in the pull request:
https://github.com/apache/spark/pull/12720#discussion_r61520953
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -866,71 +867,233 @@ class Analyzer(
* Note: CTEs are handled in CTESubstitution.
*/
object ResolveSubquery extends Rule[LogicalPlan] with PredicateHelper {
-
/**
- * Resolve the correlated predicates in the clauses (e.g. WHERE or
HAVING) of a
- * sub-query by using the plan the predicates should be correlated to.
+ * Resolve the correlated expressions in a subquery by using the an
outer plans' references. All
+ * resolved outer references are wrapped in an [[OuterReference]]
*/
- private def resolveCorrelatedSubquery(
- sub: LogicalPlan, outer: LogicalPlan,
- aliases: scala.collection.mutable.Map[Attribute, Alias]):
LogicalPlan = {
- // First resolve as much of the sub-query as possible
- val analyzed = execute(sub)
- if (analyzed.resolved) {
- analyzed
- } else {
- // Only resolve the lowest plan that is not resolved by outer
plan, otherwise it could be
- // resolved by itself
- val resolvedByOuter = analyzed transformDown {
- case q: LogicalPlan if q.childrenResolved && !q.resolved =>
- q transformExpressions {
- case u @ UnresolvedAttribute(nameParts) =>
- withPosition(u) {
- try {
- val outerAttrOpt = outer.resolve(nameParts, resolver)
- if (outerAttrOpt.isDefined) {
- val outerAttr = outerAttrOpt.get
- if (q.inputSet.contains(outerAttr)) {
- // Got a conflict, create an alias for the
attribute come from outer table
- val alias = Alias(outerAttr, outerAttr.toString)()
- val attr = alias.toAttribute
- aliases += attr -> alias
- attr
- } else {
- outerAttr
- }
- } else {
- u
- }
- } catch {
- case a: AnalysisException => u
+ private def resolveOuterReferences(plan: LogicalPlan, outer:
LogicalPlan): LogicalPlan = {
+ plan resolveOperators {
+ case q: LogicalPlan if q.childrenResolved && !q.resolved =>
+ q transformExpressions {
+ case u @ UnresolvedAttribute(nameParts) =>
+ withPosition(u) {
+ try {
+ outer.resolve(nameParts, resolver) match {
+ case Some(outerAttr) => OuterReference(outerAttr)
+ case None => u
}
+ } catch {
+ case _: AnalysisException => u
}
- }
- }
- if (resolvedByOuter fastEquals analyzed) {
- analyzed
- } else {
- resolveCorrelatedSubquery(resolvedByOuter, outer, aliases)
- }
+ }
+ }
}
}
+ /**
+ * Resolve the subqueries in a single LogicalPlan using the given
outer plans. This method
+ * alternates between applying the regular analyzer on the subquery
and applying the
+ * resolveOuterReferences rule.
+ */
+ private def resolveSubQueries(
+ plan: LogicalPlan,
+ outerPlans: Seq[LogicalPlan]): LogicalPlan = plan
transformExpressions {
+ case e: SubqueryExpression if !e.query.resolved =>
+ var previous: LogicalPlan = null
+ var current = e.query
+ do {
+ previous = current
+ // Try to resolve the subquery plan using the regular analyzer.
+ current = execute(current)
+
+ // Use the outer references to resolve the subquery plan if it
isn't resolved yet.
+ val i = outerPlans.iterator
+ while (!current.resolved && i.hasNext) {
+ current = resolveOuterReferences(current, i.next())
--- End diff --
```
do {
current = execute(current)
previous = current
val i = outerPlans.iterator
while (!current.resolved && current.fastEqual(previous) && i.hasNext) {
current = resolveOuterReferences(current, i.next())
)
} while (!current.resolved && !current.fastEquals(previous))
```
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