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https://issues.apache.org/jira/browse/HIVE-21757?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16844339#comment-16844339
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Gopal V commented on HIVE-21757:
--------------------------------

Found the other data-loss comment in RB - https://reviews.apache.org/r/66485/

"That's a REPL event & the trouble with IOW is that it also destroys commits in 
progress with the new base_n files, where n > all previous open txns."

So even if you're compacting transaction 10, if transaction 11,12 are open, you 
cannot create a base_13 until 11 & 12 are done. The compactor now blocks behind 
writes it is not compacting either.

> ACID: use a new write id for compaction's output instead of the visibility id
> -----------------------------------------------------------------------------
>
>                 Key: HIVE-21757
>                 URL: https://issues.apache.org/jira/browse/HIVE-21757
>             Project: Hive
>          Issue Type: Bug
>          Components: Transactions
>    Affects Versions: 4.0.0
>            Reporter: Vaibhav Gumashta
>            Priority: Major
>
> HIVE-20823 added support for running compaction within a transaction. To 
> control the visibility of the output directory, it uses 
> base_writeId_visibilityId, where visibilityId is the transaction id of the 
> transaction that the compactor ran in. Perhaps we can keep using the 
> base_writeId format, by allocating a new writeId for the compactor and 
> creating the new base/delta with that.



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