[
https://issues.apache.org/jira/browse/HIVE-1293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12864541#action_12864541
]
John Sichi commented on HIVE-1293:
----------------------------------
Right, you get this if for partition p.q.r in t, you add the following to the
flat lock list:
t (S)
t.p (S)
t.p.q (S)
t.p.q.r (S or X depending what the operation is)
This doesn't add a lot of extra locks in general since there are more children
than parents, it makes the low-level recipe a little simpler, and maybe makes
show locks output clearer.
It might be exactly what you are already proposing, in which case we're in
agreement.
> Concurreny Model for Hive
> -------------------------
>
> Key: HIVE-1293
> URL: https://issues.apache.org/jira/browse/HIVE-1293
> Project: Hadoop Hive
> Issue Type: New Feature
> Components: Query Processor
> Reporter: Namit Jain
> Assignee: Namit Jain
>
> Concurrency model for Hive:
> Currently, hive does not provide a good concurrency model. The only
> guanrantee provided in case of concurrent readers and writers is that
> reader will not see partial data from the old version (before the write) and
> partial data from the new version (after the write).
> This has come across as a big problem, specially for background processes
> performing maintenance operations.
> The following possible solutions come to mind.
> 1. Locks: Acquire read/write locks - they can be acquired at the beginning of
> the query or the write locks can be delayed till move
> task (when the directory is actually moved). Care needs to be taken for
> deadlocks.
> 2. Versioning: The writer can create a new version if the current version is
> being read. Note that, it is not equivalent to snapshots,
> the old version can only be accessed by the current readers, and will be
> deleted when all of them have finished.
> Comments.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
