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https://issues.apache.org/jira/browse/HIVE-11833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14746496#comment-14746496
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Alan Gates commented on HIVE-11833:
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Just to be clear, is the main motivation here to lower contention on the DB?
+1, patch looks good.
> TxnHandler heartbeat txn doesn't need to serializable DB txn level
> ------------------------------------------------------------------
>
> Key: HIVE-11833
> URL: https://issues.apache.org/jira/browse/HIVE-11833
> Project: Hive
> Issue Type: Bug
> Reporter: Sergey Shelukhin
> Assignee: Sergey Shelukhin
> Attachments: HIVE-11833.patch
>
>
> What it does is:
> 1) Update lock heartbeat time, fails if not found.
> 2) Get txn state.
> 3) If not found, look for txn in completed, fails regardless of result.
> 4) Update txn heartbeat time if not (3) and not aborted.
> All this can run the same under repeatable-reads.
> Now if it runs under read-committed, someone could
> 1) update txn state after we read it
> 2) delete txn state (moving to completed) after we read it
> 3) same for completed state
> In case of 1 we will update heartbeat for e.g. aborted txn without detecting
> it. UPD: We can change queries to detect it
> In case of 2 the update will produce 0 rows so we will detect that and can
> check completed as we already do.
> The 3 case seems like it doesn't matter.
> I don't know if (1) matters. These heartbeats happen often and can cause
> contention on the db
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