kylin do put pre-calculate results in hbase, if cude desc is below: Dimensions:letter number Measures:count in hbase the result is count letter number 1 A 1 1 A 2 1 B 1 1 B 2 1 B 3 1 B 4 count letter 2 A 4 B If i query select count(1) from table group by letter,number limit 2,it should scan the first two rows(letter number Agg groups)? when i query select count(1) from table group by letter limit 2,it should scan the two rows(letter Agg group) Do i say right?
------------------ 原始邮件 ------------------ 发件人: "a.ramonportoles";<a.ramonporto...@gmail.com>; 发送时间: 2016年10月28日(星期五) 下午3:43 收件人: "dev"<dev@kylin.apache.org>; 主题: Re: Exceed scan threshold at 10000001 hummmm but are you using "group by LO_CUSTKEY,LO_PARTKEY" And limit apply to final result no to scan rows Example: table with two columns Letter / Number A:1 A:2 B:1 B:2 B:3 B:4 select count (1), Letter from TB group by Letter limit 1 Result: 2:A Scans 2 rows select count (1), Letter from TB group by Letter limit 2 Result: 2:A 4:B Scans 2 +4 rows Alb 2016-10-28 8:33 GMT+02:00 张磊 <121762...@qq.com>: > Query1:select count(1),sum(LO_REVENUE) from lineorder group by > LO_CUSTKEY,LO_PARTKEY > LIMIT 10000 > > > I find it scan 10000 rows from HBase > > > Query2: select count(1),sum(LO_REVENUE) from lineorder group by > LO_CUSTKEY,LO_PARTKEY > LIMIT 10001 > > > I find it scan 10000001 rows from Hbase > > > I do not know why? Should not scan 10001 row? > > > The two query i scan the same HTable KYLIN_78ROC49NQY > Kylin log:Endpoint RPC returned from HTable KYLIN_78ROC49NQY > > > > > ------------------ 原始邮件 ------------------ > 发件人: "ShaoFeng Shi";<shaofeng...@apache.org>; > 发送时间: 2016年10月28日(星期五) 中午11:20 > 收件人: "dev"<dev@kylin.apache.org>; > > 主题: Re: Exceed scan threshold at 10000001 > > > > Alberto, thanks for your explaination, you got the points and is already an > Kylin expert I believe. > > In order to protect HBase and Kylin from crashing by bad queries (which > scan too many rows), Kylin add this mechnisam to interrupt when reach some > threshold. Usually in an OLAP scenario, the result wouldn't be too large. > This is also a reminder for user to rethink the design; If you really want > to get the threshold be enlarged, you can allocate more memory to Kylin and > set "kylin.query.mem.budget" to bigger value. > > 2016-10-27 18:39 GMT+08:00 Alberto Ramón <a.ramonporto...@gmail.com>: > > > NOTE: I'm not a expert on Kylin ;) > > > > Where is mandatory? No > > Where is recommended? yes > > Where bypass the threshold? No, I think this limit is hardcoded ¿? > > > > The real question must be: why this limit exists ?: (opinion) > > - The target of Kylin is Real / Near RT, limit rows --> limit response > time > > - If Your are using JDBC, this is not a good option by performance > > - Protect the HBase Coprocesor > > - Perhaps you need a new Dim, to precalculate This Aggregate or filter by > > this new Dim > > > > For Extra-Large queries, you can also check: > > -kylin.query.mem.budget= 3GB > > -hbase.server.scanner.max.result.size = 100MB (limit from HBase, you > can > > disable with -1) > > > > Good Luck, Alb > > > > 2016-10-27 11:56 GMT+02:00 张磊 <121762...@qq.com>: > > > > > Do you mean when i query, i should add where clause, > > > but in some case, the number of records > threshold, how can i do? > > > For example, order by all groups, the number of the all groups > > > > threshold > > > > > > > > > > > > > > > ------------------ 原始邮件 ------------------ > > > 发件人: "Alberto Ramón";<a.ramonporto...@gmail.com>; > > > 发送时间: 2016年10月27日(星期四) 下午5:47 > > > 收件人: "dev"<dev@kylin.apache.org>; > > > > > > 主题: Re: Exceed scan threshold at 10000001 > > > > > > > > > > > > ERROR: Scan row count exceeded threshold > > > > > > MailList > > > <http://mail-archives.apache.org/mod_mbox/kylin-user/ > > > 201608.mbox/%3CCALjEW7M_YYi7Xs55OqPdxS6pzNvD0% > 2BamN2AX3hetnF0%3D9uFnow% > > > 40mail.gmail.com%3E> > > > Kilin > > > 1787 <https://issues.apache.org/jira/browse/KYLIN-1787>v1.5.3 > > > > > > *Scan row count exceeded threshold: 1000000, please add filter > condition > > to > > > narrow down backend scan range, like where clause* > > > > > > > > > BR, Alb > > > > > > 2016-10-27 11:40 GMT+02:00 张磊 <121762...@qq.com>: > > > > > > > Hi > > > > > > > > > > > > When i query a sql, I do not know why should scan hbase? How can i > do? > > > > Thanks! > > > > > > > > > > > > Table: lineorder 12,000,000 row records > > > > Dimensions: LO_CUSTKEY,LO_PARTKEY > > > > Measures: count(1), sum(LO_REVENUE) > > > > > > > > > > > > Query SQL: select count(1),sum(LO_REVENUE) from lineorder group by > > > > LO_CUSTKEY,LO_PARTKEY order by LO_CUSTKEY,LO_PARTKEY limit 50 > > > > > > > > > > > > I build a cude with two Dimensions and two Measures(count and sum), > the > > > > size of the Htable is 98 MB, when i execute a query in insight, it > > shows > > > > Error in coprocessor; and i check the hbase log, i find blow messages > > > > > > > > > > > > 2016-10-27 02:06:13,470 INFO [B.defaultRpcServer.handler=4, > > > queue=1,port=16020] > > > > gridtable.GTScanRequest: pre aggregation is not beneficial, skip it > > > > 2016-10-27 02:06:13,470 INFO [B.defaultRpcServer.handler=4, > > > queue=1,port=16020] > > > > endpoint.CubeVisitService: Scanned 1 rows from HBase. > > > > > > > > > > > > 2016-10-27 02:24:20,884 INFO [B.defaultRpcServer.handler=6, > > > queue=0,port=16020] > > > > endpoint.CubeVisitService: Scanned 9999001 rows from HBase. > > > > 2016-10-27 02:24:20,889 INFO [B.defaultRpcServer.handler=6, > > > queue=0,port=16020] > > > > endpoint.CubeVisitService: The cube visit did not finish normally > > because > > > > scan num exceeds threshold > > > > org.apache.kylin.gridtable.GTScanExceedThresholdException: Exceed > scan > > > > threshold at 10000001 > > > > at org.apache.kylin.storage.hbase.cube.v2.coprocessor. > > > > endpoint.CubeVisitService$2.hasNext(CubeVisitService.java:267) > > > > at org.apache.kylin.storage.hbase.cube.v2. > > > HBaseReadonlyStore$1$1. > > > > hasNext(HBaseReadonlyStore.java:111) > > > > at org.apache.kylin.storage.hbase.cube.v2.coprocessor. > > > > endpoint.CubeVisitService.visitCube(CubeVisitService.java:299) > > > > at org.apache.kylin.storage.hbase.cube.v2.coprocessor. > > > > endpoint.generated.CubeVisitProtos$CubeVisitService.callMethod( > > > > CubeVisitProtos.java:3952) > > > > at org.apache.hadoop.hbase.regionserver.HRegion. > > > > execService(HRegion.java:7815) > > > > at org.apache.hadoop.hbase.regionserver.RSRpcServices. > > > > execServiceOnRegion(RSRpcServices.java:1986) > > > > at org.apache.hadoop.hbase.regionserver.RSRpcServices. > > > > execService(RSRpcServices.java:1968) > > > > at org.apache.hadoop.hbase.protobuf.generated. > > > > ClientProtos$ClientService$2.callBlockingMethod( > > ClientProtos.java:33652) > > > > at org.apache.hadoop.hbase.ipc. > RpcServer.call(RpcServer.java: > > > 2178) > > > > at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner. > > > java:112) > > > > at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop( > > > > RpcExecutor.java:133) > > > > at org.apache.hadoop.hbase.ipc. > RpcExecutor$1.run(RpcExecutor. > > > > java:108) > > > > at java.lang.Thread.run(Thread.java:745) > > > > > > > > > -- > Best regards, > > Shaofeng Shi 史少锋 >