Thank you ! But why the second (and subsequent ones) that getScanner and first next is too slowly? I think the second (and subsequent ones) should be faster .
On Wed, Jan 26, 2011 at 12:50 PM, Tatsuya Kawano <tatsuya6...@gmail.com>wrote: > Hi, > > This is because of the server-side block cache. RS reads a block of rows > from HDFS and keep the block in its cache for a while. The first next() > takes longer because the RS serves the row from HDFS, and other next() are > faster because they are served from RS's cache. > > Thanks, > > -- > Tatsuya Kawano (Mr.) > Tokyo, Japan > > > On Jan 26, 2011, at 1:23 PM, 陈加俊 <cjjvict...@gmail.com> wrote: > > > 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 <jdcry...@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 <cjjvict...@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 > -- Thanks & Best regards jiajun
