AngersZhuuuu commented on a change in pull request #26437: [SPARK-29800][SQL]
Rewrite non-correlated subquery use ScalaSubquery to optimize perf
URL: https://github.com/apache/spark/pull/26437#discussion_r363139303
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/finishAnalysis.scala
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@@ -52,6 +52,21 @@ object ReplaceExpressions extends Rule[LogicalPlan] {
}
}
+/**
+ * Rewrite non correlated exists subquery to use ScalarSubquery
+ * WHERE EXISTS (SELECT A FROM TABLE B WHERE COL1 > 10)
+ * will be rewrite to
+ * WHERE (SELECT 1 FROM (SELECT A FROM TABLE B WHERE COL1 > 10) LIMIT 1) IS
NOT NULL
+ */
+object RewriteNonCorrelatedExists extends Rule[LogicalPlan] {
Review comment:
> Shall we add a test for this rule?
I found that there is no DSL function of EXISTS. Should we add this? cc
@cloud-fan
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