[GitHub] [spark] viirya commented on a change in pull request #28975: [SPARK-32148][SS] Fix stream-stream join issue on missing to copy reused unsafe row

[GitBox <gi...@apache.org>]

viirya commented on a change in pull request #28975:
URL: https://github.com/apache/spark/pull/28975#discussion_r449689477



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File path: sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/SymmetricHashJoinStateManager.scala
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@@ -451,10 +451,25 @@ class SymmetricHashJoinStateManager(
   }
 
   private trait KeyWithIndexToValueRowConverter {
+    /** Defines the schema of the value row (the value side of K-V in state store). */
     def valueAttributes: Seq[Attribute]
 
+    /**
+     * Convert the value row to (actual value, match) pair.
+     *
+     * NOTE: implementations should ensure the result row is NOT reused during execution, as
+     * caller may use the value to store without copy().

Review comment:
       I recall in Spark SQL, there are some places similar and usually we make it as the caller's responsibility to call copy. Is this a code path critical for performance?




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