Github user ravipesala commented on a diff in the pull request: https://github.com/apache/spark/pull/3249#discussion_r22148838 --- 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 -- Ok. Done in two steps.
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