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https://issues.apache.org/jira/browse/HIVE-18570?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16459367#comment-16459367
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Gopal V commented on HIVE-18570:
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The other optimistic alternative is for the "insert into" to fail, rather than
block readers - very few people do "insert into" + "insert overwrite"
concurrently, but a lot more would do "insert overwrite" + "select"
concurrently.
> 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
> Attachments: HIVE-18570.01.patch
>
>
> 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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