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From Kyle Oba <kyle...@gmail.com>
Subject Re: Scanner Performance Question / Observation
Date Tue, 04 Aug 2009 10:06:47 GMT
Thanks for all the feedback.  We're going to spin up 0.20 to see if
the scanner time improves.  I'll try to get the times for scanner
start-up (as a percentage of total time) when we run those tests.

Much appreciated!

On Mon, Aug 3, 2009 at 3:34 PM, stack<stack@duboce.net> wrote:
> On Mon, Aug 3, 2009 at 1:58 PM, Xinan Wu <wuxinan@gmail.com> wrote:
>> 6 sec isn't crazy with 0.19. If you really want to research it, have a
>> look at where the time is spent, creating scanner or actually doing
>> the scanning. I think it's the former.
> You are probably right that it is the fomer.  In 0.19, scanners would open a
> new Reader against every file in the region before scanning could start
> (trip to namenode, then out to each dn to read in indices, etc.).  In
> 0.20.0, the already-open files are used.
> St.Ack

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