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

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-24291?focusedWorklogId=502687&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-502687 ]

ASF GitHub Bot logged work on HIVE-24291:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 20/Oct/20 13:34
            Start Date: 20/Oct/20 13:34
    Worklog Time Spent: 10m 
      Work Description: pvargacl opened a new pull request #1592:
URL: https://github.com/apache/hive/pull/1592


   
   
   ### What changes were proposed in this pull request?
   Compaction cleaner should wait for all previous txns to commit
   
   ### Why are the changes needed?
   Example buggy scenario in the Jira
   
   
   ### Does this PR introduce _any_ user-facing change?
   No
   
   
   ### How was this patch tested?
   Unit tests
   


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Issue Time Tracking
-------------------

            Worklog Id:     (was: 502687)
    Remaining Estimate: 0h
            Time Spent: 10m

> 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
>          Time Spent: 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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