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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 17:24:43 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1566?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13789414#comment-13789414
] 

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

Commit 0d85d60c08f88bc6d3e366b192fba5a371654363 in branch refs/heads/master from [~elserj]
[ https://git-wip-us.apache.org/repos/asf?p=accumulo.git;h=0d85d60 ]

ACCUMULO-1566 Lift out the implicit "3 batch" convention from ScannerIterator
into Scanner so it can be configured by the user.

The ScannerIterator previously started pre-fetching the next batch after the
previous was returned, only after three batches are returned. Clients have the
ability to know how to control this better, and, as such, we should let them.


> 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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