dilipbiswal 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_r344250658
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/subquery.scala
##########
@@ -171,6 +171,63 @@ 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[Boolean] = null)
+ extends ExecSubqueryExpression {
+
+ @transient private var result: Boolean = _
+
+ 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 = {
+ result = !plan.execute().isEmpty()
Review comment:
@cloud-fan @AngersZhuuuu Thanks for pinging me. Just for me to understand,
since we refer to another pr in this pr.
So we are considering planning the Subqueries appearing inside ON clause as
a Join, right ?
Assuming above, so if the query was :
```
SELECT * FROM T1 JOIN T2 ON T1.C1 = T2.C1 AND T1.C1 EXISTS (SELECT 1 FROM T3
WHERE T1.C1 = T3.C1)
```
We are considering to plan it as :
```
(T1 LeftSemi T3 ON T1.C1 = T3.C1) Join T2 ON T1.C1 = T2.C2
```
This Looks okay to me for inner joins. I am just not sure about outer
joins.. What do you think Wenchen ?
Now, coming to the non-correlated subqueries, if we keep it as a
PlanExpression and execute it, one thing we have to see is "what is the join
strategy thats being picked". Its always going to be broadcast nested loop as
it won't be a "equi-join" ? right ?
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