Hi James, Thank you for reminding me of that. Cheers, Weiping > Hi Weiping, > Take a look at Apache Phoenix (http://phoenix.incubator.apache.org/). It's > a SQL layer on top of HBase and has support for LIMIT and a query planner > and optimizer. > Thanks, > James > > > On Mon, Mar 17, 2014 at 12:19 PM, Weiping Qu <q...@informatik.uni-kl.de>wrote: > >> I am doing a mult-thread(100) scan test over hbase. >> If one request with given key-range matches a large number of >> correspoding rows in hbase, my request is waiting for this scan to >> complete. >> The throughput is really slow. >> For test purpose, I'd like to use LIMIT to reduce the time on scanning >> and transferring results back from hbase to increase the throughput. >> Do you think the "hbase.client.scan.max.result.size" or >> setMaxResultSize(in bytes) could help HBase to stop scan at the LIMIT >> before scanning complete corresponding rows? >> >> As you mentioned that there is no query optimizer in HBase, I assume >> that region servers will not stop scanning the rows in this key-range in >> this case until it gets all the results and limit the results to max >> size which is sent to the client. >> If so, there is not much I can do to compare the throughput with that in >> relational databases like MySQL. >> >> Thanks, >> Cheers. >>> Limit clause in SQL Select statement makes sense because it allows query >> optimizer to plan accordingly. >>> It does not make sense in HBase as since there is no query planner and >> or optimization involved during >>> scanning HBase table. You can easily mimic this functionality on a >> client side (I mean - limit). >>> Best regards, >>> Vladimir Rodionov >>> Principal Platform Engineer >>> Carrier IQ, www.carrieriq.com >>> e-mail: vrodio...@carrieriq.com >>> >>> ________________________________________ >>> From: Weiping Qu [q...@informatik.uni-kl.de] >>> Sent: Monday, March 17, 2014 4:48 AM >>> To: dev@hbase.apache.org >>> Subject: Re: 答复: setMaxResultSize method in Scan >>> >>> Thanks. >>> >>> I'd like to assume that setMaxResultSize is equivalent to the SQL Limit >>> clause as expected which is specified each time a SQL statement is >>> executed . >>> Now through "hbase.client.scanner.max.result.size" can the limitation of >>> number of row returned only apply to all the scanner instances. >>> I am wondering why the setMaxResultSize is removed now. >>> >>>> No such method for Scan in 0.94.x. >>>> >>>> If you want to set the max result size for a scan, you can achieve this >> by setting the "hbase.client.scanner.max.result.size" configuration, the >> default for which is Long.MAX_VALUE (no limited) >>>> ________________________________________ >>>> 发件人: Weiping Qu [q...@informatik.uni-kl.de] >>>> 发送时间: 2014年3月17日 18:50 >>>> 收件人: dev@hbase.apache.org >>>> 主题: setMaxResultSize method in Scan >>>> >>>> Hello, >>>> >>>> I could not find the method setMaxResultSize(long m) >>>> ( >> http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Scan.html) >>>> in my Scanclass (0.94.13 version). >>>> Can anyone help me? Thanks >>>> >>>> Weiping >>> -- >>> Mit freundlichen Grü?en / Kind Regards >>> >>> *Weiping Qu* >>> >>> University of Kaiserslautern >>> Department of Computer Science >>> Heterogeneous Information Systems Group >>> P.O. Box 3049 >>> 67653 Kaiserslautern, Germany >>> >>> Email: qu (at) informatik.uni-kl.de >>> Phone: +49 631 205 3264 >>> Fax: +49 631 205 3299 >>> Room: 36/331 >>> >>> Confidentiality Notice: The information contained in this message, >> including any attachments hereto, may be confidential and is intended to be >> read only by the individual or entity to whom this message is addressed. If >> the reader of this message is not the intended recipient or an agent or >> designee of the intended recipient, please note that any review, use, >> disclosure or distribution of this message or its attachments, in any form, >> is strictly prohibited. If you have received this message in error, please >> immediately notify the sender and/or notificati...@carrieriq.com and >> delete or destroy any copy of this message and its attachments. >> >> >> -- >> Mit freundlichen Grü?en / Kind Regards >> >> *Weiping Qu* >> >> University of Kaiserslautern >> Department of Computer Science >> Heterogeneous Information Systems Group >> P.O. Box 3049 >> 67653 Kaiserslautern, Germany >> >> Email: qu (at) informatik.uni-kl.de >> Phone: +49 631 205 3264 >> Fax: +49 631 205 3299 >> Room: 36/331 >>
-- Mit freundlichen Grü?en / Kind Regards *Weiping Qu* University of Kaiserslautern Department of Computer Science Heterogeneous Information Systems Group P.O. Box 3049 67653 Kaiserslautern, Germany Email: qu (at) informatik.uni-kl.de Phone: +49 631 205 3264 Fax: +49 631 205 3299 Room: 36/331
