[GitHub] [spark] cloud-fan commented on issue #24467: [SPARK-27568][CORE] Fix readLock leak while calling take()/first() on a cached rdd

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cloud-fan commented on issue #24467: [SPARK-27568][CORE] Fix readLock leak while calling take()/first() on a cached rdd
URL: https://github.com/apache/spark/pull/24467#issuecomment-489882706
 
 
   This reminds me of the memory leak issue in sort-merge-join.
   
   We use scala `Iterator` to exchange data between SQL operators/RDDs, and we can only do the cleanup work when the `Iterator` is consumed up, or in a task completion listener.
   
   But what we really need is a traditional database iterator, with `open`, `next`, `get` and `close` methods. When a downstream operator finishes its work without consuming up the input data, it can call `close` to do free the resource.
   
   For this particular case, I think using a task completion listener is good enough?

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