[GitHub] [spark] ulysses-you commented on a diff in pull request #41046: [SPARK-43376][SQL] Improve reuse subquery with table cache

["ulysses-you (via GitHub)" <gi...@apache.org>]

ulysses-you commented on code in PR #41046:
URL: https://github.com/apache/spark/pull/41046#discussion_r1185645621


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sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/ReuseAdaptiveSubquery.scala:
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@@ -33,10 +33,13 @@ case class ReuseAdaptiveSubquery(
 
     plan.transformAllExpressionsWithPruning(_.containsPattern(PLAN_EXPRESSION)) {
       case sub: ExecSubqueryExpression =>
-        val newPlan = reuseMap.getOrElseUpdate(sub.plan.canonicalized, sub.plan)
-        if (newPlan.ne(sub.plan)) {
-          sub.withNewPlan(ReusedSubqueryExec(newPlan))
-        } else {
+        // `InsertAdaptiveSparkPlan` compiles subquery for each exprId, then the java object
+        // is always `eq` if two subqueries have same exprId.
+        // Check if the subquery can be reused manually instead of call `getOrElseUpdate`.
+        reuseMap.get(sub.plan.canonicalized).map { subquery =>
+          sub.withNewPlan(ReusedSubqueryExec(subquery))
+        }.getOrElse {
+          reuseMap.put(sub.plan.canonicalized, sub.plan)

Review Comment:
   The behavior should be same with `getOrElseUpdate`. I changed `put` to `putIfAbsent` to fully equivalent with `getOrElseUpdate` that the first `put` will win if there is race condition.



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