[jira] [Commented] (HIVE-14907) Hive Metastore should use repeatable-read consistency level

["Michael Smith (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-14907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17723749#comment-17723749 ] 

Michael Smith commented on HIVE-14907:
--------------------------------------

The current version of DataNucleus fails if repeatable-read is configured while using Oracle database. It should fall back to serializable, except DataNucleus incorrectly expects Oracle to support repeatable-read.

> Hive Metastore should use repeatable-read consistency level
> -----------------------------------------------------------
>
>                 Key: HIVE-14907
>                 URL: https://issues.apache.org/jira/browse/HIVE-14907
>             Project: Hive
>          Issue Type: Bug
>          Components: Metastore
>    Affects Versions: 2.2.0
>            Reporter: Lenni Kuff
>            Priority: Major
>
> Currently HMS uses the "read-committed" consistency level which is the default for DataNucleus. This could cause potential problems since the state visible to each transaction can actually see updates from other transactions,  so it is very difficult to reason about any code that reads multiple pieces of data.
> Instead it should use "repeatable-read" consistency which guarantees that any transaction only sees the state at the beginning of a transaction plus any updates done within a transaction.



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