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From "Lefty Leverenz (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-1293) Concurrency Model for Hive
Date Sun, 13 Nov 2016 07:54:59 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15661064#comment-15661064
] 

Lefty Leverenz commented on HIVE-1293:
--------------------------------------

Doc note:  This adds several configuration parameters to HiveConf.java:

*  hive.lockmgr.zookeeper.default.partition.name
*  hive.support.concurrency
*  hive.lock.manager
*  hive.lock.numretries
*  hive.lock.sleep.between.retries
*  hive.zookeeper.quorum
*  hive.zookeeper.client.port
*  hive.zookeeper.session.timeout

They are documented in the wiki here:

* [Configuration Properties -- Locking | https://cwiki.apache.org/confluence/display/Hive/Configuration+Properties#ConfigurationProperties-Locking]

> Concurrency Model for Hive
> --------------------------
>
>                 Key: HIVE-1293
>                 URL: https://issues.apache.org/jira/browse/HIVE-1293
>             Project: 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.1293.7.patch, hive.1293.8.patch, hive.1293.9.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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