[jira] [Assigned] (HIVE-26704) Cleaner shouldn't be blocked by global min open txnId

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

     [ https://issues.apache.org/jira/browse/HIVE-26704?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Denys Kuzmenko reassigned HIVE-26704:
-------------------------------------

    Assignee: Denys Kuzmenko

> Cleaner shouldn't be blocked by global min open txnId
> -----------------------------------------------------
>
>                 Key: HIVE-26704
>                 URL: https://issues.apache.org/jira/browse/HIVE-26704
>             Project: Hive
>          Issue Type: Task
>            Reporter: Denys Kuzmenko
>            Assignee: Denys Kuzmenko
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> *Single transaction blocks cluster-wide Cleaner operations*
> Currently, if there is a single long-running transaction that can prevent the Cleaner to clean up any tables. This causes file buildup in tables, which can cause performance penalties when listing the directories (note that the compaction is not blocked by this, so unnecessary data is not read, but the files remain there which causes performance penalty). 
> We can reduce the protected files from the open transaction if we have query-table correlation data stored in the backend DB, but this change will need the current method of recording that detail to be revisited. 
> The naive and somewhat backward-compatible approach is to capture the minOpenWriteIds per table. It involves a non-mutation operation (as in, there is no need for the HMS DB to wait for another user’s operation to record it). This does spew data writes into the HMS backend DB, but this is a blind insert operation that can be group-committed across many users. 



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