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From "Duo Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17917) Use pread by default for all user scan
Date Sat, 29 Apr 2017 05:44:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17917?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15989776#comment-15989776
] 

Duo Zhang commented on HBASE-17917:
-----------------------------------

Yeah we should change the title but seems it will be very long since this patch also creates
a separated reader for streaming read...

1. Yeah I can imagine, under this scenario default will perform worse than stream. And under
some other scenario default will perform worse than pread. For example, you reopen the scanner
but the scanner is closed without read any new data... But in most cases I think it is good
enough? User can set the ReadType explicitly if he/she knows which one is better. And we can
also keep improving the trySwitchToStreamRead method to make it more intelligent.

2. 2.7.3 so I think it contains the fix.

3. I haven't collected the information since this is not a stress test and the DN is not overloaded.
Will collect the information next time when I'm back. Out for vacation in the next 3 days.

Thanks.

> Use pread by default for all user scan
> --------------------------------------
>
>                 Key: HBASE-17917
>                 URL: https://issues.apache.org/jira/browse/HBASE-17917
>             Project: HBase
>          Issue Type: Sub-task
>          Components: scan
>    Affects Versions: 2.0.0
>            Reporter: Duo Zhang
>            Assignee: Duo Zhang
>             Fix For: 2.0.0
>
>         Attachments: HBASE-17917.patch, HBASE-17917-v1.patch, HBASE-17917-v2.patch, HBASE-17917-v2.patch,
HBASE-17917-v3.patch, HBASE-17917-v4.patch, HBASE-17917-v5.patch
>
>
> As said in the parent issue. We need some benchmark here first.



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