[jira] [Created] (HIVE-17411) LLAP IO may incorrectly release a refcount in some cases

["Sergey Shelukhin (JIRA)" <ji...@apache.org>]

Sergey Shelukhin created HIVE-17411:
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             Summary: LLAP IO may incorrectly release a refcount in some cases
                 Key: HIVE-17411
                 URL: https://issues.apache.org/jira/browse/HIVE-17411
             Project: Hive
          Issue Type: Bug
            Reporter: Sergey Shelukhin
            Assignee: Sergey Shelukhin


Not sure why this doesn't happen much more often, actually.
In a large stream whose buffers are not reused (e.g. a dictionary, that is locked once for all RGs), separated into many buffers (e.g. due to a small ORC compression buffer size), it may happen that some, but not all, buffers are evicted from cache.
If CacheBuffer follows BufferChunk in the buffer list, the latter will be converted to ProcCacheChunk;  it is possible for early refcount release logic from the former to release the refcount (for a dictionary it would always be released cause by definition there's no reuse), and then backtrack to the latter, and try to decref an uninitialized MemoryBuffer in ProcCacheChunk because ProcCacheChunk looks like a CacheChunk. PCC initial refcounts are released separately after the data is uncompressed.



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