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https://issues.apache.org/jira/browse/HIVE-15988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15901394#comment-15901394
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Gopal V commented on HIVE-15988:
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The delete deltas are still really small in memory, so this is more of a
hypothetical concern for a large cache (~4 bits per delete row?).
Looks like we already have a configuration parameter which changes the way ACID
deletes are read into memory, which can also apply to the caching operations -
{{hive.transactional.events.mem}}
> 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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