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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12031) Parallel Scanners inside Region
Date Tue, 23 Sep 2014 19:55:36 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12031?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14145330#comment-14145330
] 

stack commented on HBASE-12031:
-------------------------------

A few high-level comments [~vrodionov]

You are adding a HFIleReaderContext.  We have a HFileContext already.  You cannot reuse/amend
this class to your purposes?

I would not expect a Context to do the actual reading as in +  public boolean read(long offset,
byte[] buffer, int bufOffset, int len). I could imagine passing in a context when you read.

Regards read-ahead and keeping the buffer local to the scanner, it is not enough just  having
the scanner do a read-ahead that ensures blockcache is populated?  You have to bring the data
local to the scanner? If multiple concurrent scans, we'll have duplicate data buffered?

Hard to see what you did in readAtOffset.

Keep going...





> Parallel Scanners inside Region
> -------------------------------
>
>                 Key: HBASE-12031
>                 URL: https://issues.apache.org/jira/browse/HBASE-12031
>             Project: HBase
>          Issue Type: New Feature
>          Components: Performance, Scanners
>    Affects Versions: 0.98.6
>            Reporter: Vladimir Rodionov
>            Assignee: Vladimir Rodionov
>             Fix For: 1.0.0, 2.0.0, 0.98.7, 0.99.1
>
>         Attachments: HBASE-12031.2.patch, HBASE-12031.3.patch, HBASE-12031.patch, ParallelScannerDesign.pdf,
hbase-12031-tests.tar.gz
>
>
> This JIRA to improve performance of multiple scanners running on a same region in parallel.
The scenarios where we will get the performance benefits:
> * New TableInputFormat with input splits smaller than HBase Region.
> * Scanning during compaction (Compaction scanner and application scanner over the same
Region).
> Some JIRAs related to this one:
> https://issues.apache.org/jira/browse/HBASE-7336
> https://issues.apache.org/jira/browse/HBASE-5979 



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