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Posted to dev@hive.apache.org by "John Sichi (JIRA)" <ji...@apache.org> on 2010/08/20 00:33:19 UTC
[jira] Updated: (HIVE-1293) Concurrency Model for Hive
[ https://issues.apache.org/jira/browse/HIVE-1293?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
John Sichi updated HIVE-1293:
-----------------------------
Summary: Concurrency Model for Hive (was: Concurreny Model for Hive)
> Concurrency 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
> Fix For: 0.7.0
>
> Attachments: hive.1293.1.patch, hive.1293.2.patch, hive.1293.3.patch, hive.1293.4.patch, hive.1293.5.patch, hive.1293.6.patch, hive_leases.txt
>
>
> 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.
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