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From "ASF subversion and git services (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-1566) Add ability for client to start Scanner readahead immediately
Date Tue, 08 Oct 2013 17:24:44 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1566?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13789416#comment-13789416
] 

ASF subversion and git services commented on ACCUMULO-1566:
-----------------------------------------------------------

Commit dab1be962b6ab1ab095c4ccf7f3995ab1208c3d7 in branch refs/heads/master from [~elserj]
[ https://git-wip-us.apache.org/repos/asf?p=accumulo.git;h=dab1be9 ]

ACCUMULO-1566 Add in an integration-test which checks that the readahead
configuration works as intended.

By applying the SlowIterator to sleep on next(), and then sleep for the same
amount of time in the main loop over the iterator from the Scanner, we should
only have to wait once when we're in "readahead mode", but wait twice when we're
not.


> Add ability for client to start Scanner readahead immediately
> -------------------------------------------------------------
>
>                 Key: ACCUMULO-1566
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-1566
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: client
>            Reporter: Josh Elser
>            Assignee: Josh Elser
>             Fix For: 1.6.0
>
>
> When the client cares about getting results in sorted order, the BatchScanner, as nice
as it is, is mostly irrelevant.
> One interesting property of the Scanner is that it will begin to pre-fetch more results
after the 3rd batch of results has been fetched from the server.
> Clients may have an idea of the number of records that will be returned by a scan, and
thus will have an idea about how they want to control such a readahead. It would be nice to
allow the client to control after how many batches the readahead thread starts.



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