[jira] (HIVE-24291) Compaction Cleaner prematurely cleans up deltas

["Denys Kuzmenko (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-24291 ]


    Denys Kuzmenko deleted comment on HIVE-24291:
    ---------------------------------------

was (Author: dkuzmenko):
Merged to master.
[~kkasa], thank you for the review!

> Compaction Cleaner prematurely cleans up deltas
> -----------------------------------------------
>
>                 Key: HIVE-24291
>                 URL: https://issues.apache.org/jira/browse/HIVE-24291
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Peter Varga
>            Assignee: Peter Varga
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 4.0.0-alpha-1
>
>          Time Spent: 2h 10m
>  Remaining Estimate: 0h
>
> Since HIVE-23107 the cleaner can clean up deltas that are still used by running queries.
> Example:
>  * TxnId 1-5 writes to a partition, all commits
>  * Compactor starts with txnId=6
>  * Long running query starts with txnId=7, it sees txnId=6 as open in its snapshot
>  * Compaction commits
>  * Cleaner runs
> Previously min_history_level table would have prevented the Cleaner to delete the deltas1-5 until txnId=7 is open, but now they will be deleted and the long running query may fail if its tries to access the files.
> Solution could be to not run the cleaner until any txn is open that was opened before the compaction was committed (CQ_NEXT_TXN_ID)



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