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https://issues.apache.org/jira/browse/HIVE-15988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15901370#comment-15901370
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Gopal V commented on HIVE-15988:
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[~teddy.choi]: the delete deltas pose a deadlock possibility - since they are
not opened one by one, but all at the same time, they have the possibility of
locking out the entire cache under some circumstances (i.e all deltas are open,
but not all have been consumed).
This is not the case with the insert deltas, since only one will be opened per
split at a time, with the previous one being closed before the next one is
opened - the eviction behaviour is much more easy to model.
> LLAP: cache ORC ACID delete deltas
> ----------------------------------
>
> Key: HIVE-15988
> URL: https://issues.apache.org/jira/browse/HIVE-15988
> Project: Hive
> Issue Type: Improvement
> Components: llap, Transactions
> Reporter: Teddy Choi
> Assignee: Teddy Choi
> Attachments: HIVE-15988.1.patch
>
>
> HIVE-12631 implemented ORC ACID table support in LLAP. If we cache ACID
> delete delta in LLAP, it will be faster.
> The cache is currently low-level (CB-level in ORC), so we could just use it
> to read bases and deltas (deltas should be cached with higher priority) and
> merge as usual. We could also cache merged representation in future.
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