Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/3249#discussion_r22004038
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -314,6 +318,113 @@ class Analyzer(catalog: Catalog, registry:
FunctionRegistry, caseSensitive: Bool
protected def containsStar(exprs: Seq[Expression]): Boolean =
exprs.collect { case _: Star => true }.nonEmpty
}
+
+ /**
+ * Transforms the query which has subquery expressions in where clause
to join queries.
+ * Case 1 Uncorelated queries
+ * -- original query
+ * select C from R1 where R1.A in (Select B from R2)
+ * -- rewritten query
+ * Select C from R1 left semi join (select B as sqc0 from R2) subquery
on R1.A = subquery.sqc0
+ *
+ * Case 2 Corelated queries
+ * -- original query
+ * select C from R1 where R1.A in (Select B from R2 where R1.X = R2.Y)
+ * -- rewritten query
+ * select C from R1 left semi join (select B as sqc0, R2.Y as sqc1 from
R2) subquery
+ * on R1.X = subquery.sqc1 and R1.A = subquery.sqc0
+ *
+ * Refer:
https://issues.apache.org/jira/secure/attachment/12614003/SubQuerySpec.pdf
+ */
+ object SubQueryExpressions extends Rule[LogicalPlan] {
+
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ case filter @ Filter(conditions, child) =>
+ val subqueryExprs = new
scala.collection.mutable.ArrayBuffer[SubqueryExpression]()
+ val nonSubQueryConds = new
scala.collection.mutable.ArrayBuffer[Expression]()
+ val transformedConds = conditions.transform{
--- End diff --
Space before `{`.
Also I would consider doing this in two steps to avoid depending on
transform for side effects: a collect to get the list and then a transform to
replace with `true`.
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