[jira] [Assigned] (HIVE-18570) ACID IOW implemented using base may delete too much data

["Eugene Koifman (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-18570?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Eugene Koifman reassigned HIVE-18570:
-------------------------------------

    Assignee: Eugene Koifman

> ACID IOW implemented using base may delete too much data
> --------------------------------------------------------
>
>                 Key: HIVE-18570
>                 URL: https://issues.apache.org/jira/browse/HIVE-18570
>             Project: Hive
>          Issue Type: Bug
>          Components: Transactions
>            Reporter: Sergey Shelukhin
>            Assignee: Eugene Koifman
>            Priority: Blocker
>
> Suppose we have a table with delta_0 insert data.
> Txn 1 starts an insert into delta_1.
> Txn 2 starts an IOW into base_2.
> Txn 2 commits.
> Txn 1 commits after txn 2 but its results would be invisible.
> Txn 2 deletes rows committed by txn 1 that according to standard ACID semantics it could have never observed and affected; this sequence of events is only possible under read-uncommitted isolation level (so, 2 deletes rows written by 1 before 1 commits them). 
> This is if we look at IOW as transactional delete+insert. Otherwise we are just saying IOW performs "semi"-transactional delete.
> If 1 ran an update on rows instead of an insert, and 2 still ran an IOW/delete, row lock conflict (or equivalent) should cause one of them to fail.



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