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From 陈加俊 <cjjvict...@gmail.com>
Subject Re: How to improve the speed of HTable scan
Date Wed, 26 Jan 2011 04:23:30 GMT
 final Scan scan = new Scan();
 scan.setCaching(1);
 scan.addColumn(family);
 ResultScanner  rs=table.getScanner(scan);

the speed is:

getTableScanner 2.28
next 27s832.12ms
next 0.99ms
next 0.94ms
next 0.82ms
next 0.94ms
next 0.88ms
next 0.95ms
next 0.94ms
next 1.37ms
next 0.90ms
next 0.89ms
next 0.90ms
next 0.91ms
next 0.86ms
next 1.23ms
next 0.87ms
next 0.87ms
next 0.83ms
next 0.87ms
next 0.90ms
next 0.91ms
next 1.73ms
next 0.98ms
next 0.89ms
next 0.86ms
next 0.92ms
next 1.33ms
next 0.87ms
next 0.89ms
next 0.82ms
next 0.87ms
next 0.84ms
next 0.94ms
next 0.96ms
next 0.93ms
next 0.79ms
next 0.82ms
next 0.84ms
next 0.84ms
next 0.87ms
next 1.17ms
next 0.80ms
next 1.25ms
next 1.08ms
next 1.08ms
next 1.95ms
next 1.66ms

....

getTableScanner 0.98ms
next 16s258.33ms
next 0.95ms
next 1.10ms
next 1.06ms
next 0.90ms
next 2.13ms
next 2.31ms
next 1.02ms
next 1.38ms
next 0.97ms
next 0.90ms
next 0.85ms
next 2.03ms
next 1.01ms
next 1.35ms
next 1.05ms
next 1.06ms
next 1.02ms
next 1.28ms
next 0.94ms
next 1.35ms
next 0.86ms
next 0.86ms
next 0.88ms
next 0.83ms
next 0.92ms
next 0.92ms
next 1.09ms
next 0.91ms
...

Why the first next is too slowly ?

HBase-0.20.6



On Wed, Jan 26, 2011 at 2:09 AM, Jean-Daniel Cryans <jdcryans@apache.org>wrote:

> Caching is the number of rows that will be fetched per RPC, depending
> on how big your rows are you might want to set it larger or smaller.
> Try 10 then do some experiments.
>
> There's not that many more, speed of reading is always improved with
> caching. Make sure your data can fit in the block cache and that it
> stays there.
>
> J-D
>
> On Tue, Jan 25, 2011 at 2:35 AM, 陈加俊 <cjjvictory@gmail.com> wrote:
> >  final Scan scan = new Scan();
> >  scan.setCaching(scannerCaching);
> >  scan.addColumn(family);
> >
> >  table.getScanner(scan);
> >
> > For improving  the speed of scan .
> > How to adjust the parameters ? Is there any more parameters or methods
> that
> > I don't know.
> >
>



-- 
Thanks & Best regards
jiajun

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