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From "Andrew Mains (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-7805) Support running multiple scans in hbase-handler
Date Fri, 19 Sep 2014 22:04:34 GMT

    [ https://issues.apache.org/jira/browse/HIVE-7805?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14141390#comment-14141390
] 

Andrew Mains commented on HIVE-7805:
------------------------------------

[~swarnim] yes, definitely! Thanks a lot for the review. Reviewboard review is here: https://reviews.apache.org/r/25850/
. 

Let me know if you need me to rebase against the latest trunk or anything else.

> Support running multiple scans in hbase-handler
> -----------------------------------------------
>
>                 Key: HIVE-7805
>                 URL: https://issues.apache.org/jira/browse/HIVE-7805
>             Project: Hive
>          Issue Type: Improvement
>          Components: HBase Handler
>    Affects Versions: 0.14.0
>            Reporter: Andrew Mains
>            Assignee: Andrew Mains
>            Priority: Minor
>         Attachments: HIVE-7805.1.patch, HIVE-7805.patch
>
>
> Currently, the HiveHBaseTableInputFormat only supports running a single scan. This can
be less efficient than running multiple disjoint scans in certain cases, particularly when
using a composite row key. For instance, given a row key schema of:
> {code}
> struct<bucket int, time timestamp>
> {code}
> if one wants to push down the predicate:
> {code}
> bucket IN (1, 10, 100) AND timestamp >= 1408333927 AND timestamp < 1408506670
> {code}
> it's much more efficient to run a scan for each bucket over the time range (particularly
if there's a large amount of data per day). With a single scan, the MR job has to process
the data for all time for buckets in between 1 and 100.
> hive should allow HBaseKeyFactory's to decompose a predicate into one or more scans in
order to take advantage of this fact.



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