AngersZhuuuu commented on a change in pull request #26437: [SPARK-29800][SQL]
Plan Exists 's subquery in PlanSubqueries
URL: https://github.com/apache/spark/pull/26437#discussion_r344188653
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/subquery.scala
##########
@@ -171,6 +171,69 @@ case class InSubqueryExec(
}
}
+/**
+ * The physical node of exists-subquery. This is for support use exists in
join's on condition,
+ * since some join type we can't pushdown exists condition, we plan it here
+ */
+case class ExistsExec(child: Expression,
+ subQuery: String,
+ plan: BaseSubqueryExec,
+ exprId: ExprId,
+ private var resultBroadcast: Broadcast[Array[Any]] =
null)
+ extends ExecSubqueryExpression {
+
+ @transient private var result: Array[Any] = _
+
+ override def dataType: DataType = BooleanType
+ override def children: Seq[Expression] = child :: Nil
+ override def nullable: Boolean = child.nullable
+ override def toString: String = s"EXISTS ${plan.name}"
+ override def withNewPlan(plan: BaseSubqueryExec): ExistsExec = copy(plan =
plan)
+
+ override def semanticEquals(other: Expression): Boolean = other match {
+ case in: ExistsExec => child.semanticEquals(in.child) &&
plan.sameResult(in.plan)
+ case _ => false
+ }
+
+
+ def updateResult(): Unit = {
+ val rows = plan.executeCollect()
Review comment:
> The reason why we don't have a physical plan for Exists is: it's not
robust. Collecting the entire result of a query plan at the driver side is very
likely to hit OOM. That's why we have to convert Exists to a join.
We can make it just return rdd.isEmpy() since exists just need to judge if
result is empty.
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