Github user yhuai commented on a diff in the pull request:
https://github.com/apache/spark/pull/9055#discussion_r42581785
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -270,6 +273,146 @@ class Analyzer(
}
/**
+ * Rewrite the [[Exists]] [[In]] with left semi join or anti join.
+ */
+ object RewriteFilterSubQuery extends Rule[LogicalPlan] with
PredicateHelper {
+ def unapply(condition: Expression): Option[(Expression,
Seq[Expression])] = {
+ if (condition.resolved == false) {
+ return None
+ }
+
+ val conjuctions = splitConjunctivePredicates(condition).map(_
transformDown {
+ // Remove the Cast expression for SubQueryExpression.
+ case Cast(f: SubQueryExpression, BooleanType) => f
+ }
+ )
+
+ val (subqueries, others) = conjuctions.partition(c =>
c.isInstanceOf[SubQueryExpression])
+ if (subqueries.isEmpty) {
+ None
+ } else if (subqueries.length > 1) {
+ throw new AnalysisException(
+ s"Only 1 SubQuery expression is supported, but we got
$subqueries")
+ } else {
+ val subQueryExpr = subqueries(0).asInstanceOf[SubQueryExpression]
+ // try to resolve the subquery
+
+ val subquery = Analyzer.this.execute(subQueryExpr.subquery) match {
+ case Distinct(child) => child // Distinct is useless for semi
join, ignore it.
--- End diff --
Can you add comment to explain when we will get a `Distinct`?
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