final Pair<byte[][], byte[][]> ranges = table.getStartEndKeys(); final byte[][] startKeys = ranges.getFirst(); final byte[][] endKeys = ranges.getSecond();
I scan the first range and delete the rows,and get the second range and delete the rows. But I find the ranges is not changed after about 5 minutes. 2011/1/26 Stack <[email protected]> > We do an RPC to open a Scanner. The open returns Scanner id to use > subsequently. We then next. If caching is not enabled, we'll do an > RPC per next invocation. Otherwise every N invocations. Perhaps > the slowdown on first next is because its doing open RPC then a new > RPC that is pre-fetching a bunch of rows? > > St.Ack > > On Tue, Jan 25, 2011 at 9:36 PM, 陈加俊 <[email protected]> wrote: > > 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 <[email protected] > >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 <[email protected]> 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 < > [email protected] > >> >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 <[email protected]> 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 > > > -- Thanks & Best regards jiajun
