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From "Keith Turner (JIRA)" <j...@apache.org>
Subject [jira] [Reopened] (ACCUMULO-1566) Add ability for client to start Scanner readahead immediately
Date Tue, 08 Oct 2013 19:08:43 GMT

     [ https://issues.apache.org/jira/browse/ACCUMULO-1566?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Keith Turner reopened ACCUMULO-1566:
------------------------------------


[~elserj] read ahead also happens on the server side.   When the pipeline is fully spun two
threads will be running on the tserver (one reading data from rfiles and one transfering data
to client) and two threads on the client (one transfering data from server and one processing
data).   The server side currently has a hard coded trigger of three batches for spinning
up the extra thread.   Should probably pass the threshold from the client side and use it
for the server side scan session.

> 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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